XiphWiki - User contributions [en]

Work In Progress

2009-09-06T18:38:11Z

Decoy: the draft stuff has been settled, comments have been solicited, and while no formal decision has been made, the format has stabilised enough to stagnate for over two years

* '''General Usage:'''
** [[Metadata]]: Various types of Ogg metadata including the [[M3F]] (Multimedia Metadata Format) and [[XMLEmbedding]]
** [[MIME_Types_and_File_Extensions]]: MIME Types and file extensions for Ogg multimedia files
** [[Subtle]]: Subtitling tool for professional use that intends to support most subtitle formats including CMML and OggKate
** [[OggText]]: A generic media mapping for (discontinuous) text codecs into Ogg
** [[ROE]]: A description format for describing the tracks and languages etc. of an Ogg multitrack composition

* '''Compressed Codecs:'''
** [[Theora]] 1.1 "thusnelda": improving compression efficiency while keeping compatibility, see [[Theora11Todo]]
** [[OggDirac]]: The "next-generation" wavelet based video codec, lossy or lossless
** [[OggCELT]]: A low-latency audio codec
** [[OggMNG]]: A mapping for encapsulating the MNG animation format in Ogg

* '''Uncompressed Codecs:'''
** [[OggKate]]: A codec for karaoke and text encapsulation in Ogg
** [[OggPCM]]: Uncompressed PCM audio, currently being implemented
** [[OggSpots]]: A mapping for encapsulating timed images in Ogg
** [[OggUVS]]: Uncompressed RGB and YUV video, under active development (preferred to OggRGB and OggYUV).

* '''Abandonware''' (nobody working on those as far as we know)
** [[Ghost]]: A "next-generation" audio codec (vapourware so far -- don't hold your breath)
** [[Oggless]]: Embedding Xiph codecs like Vorbis in containers other than Ogg
** [[IceShare]]: P2P content distribution
** [[OggPCM_Draft1]]: Original uncompressed PCM audio proposal
** [[OggRGB]]: Original uncompressed RGB video proposal
** [[OggWrit]]: Text phrase codec (e.g. subtitles)
** [[OggYUV]]: Original uncompressed YUV video proposal

[[Category:Developers stuff]]

OggPCM

2009-09-06T18:06:17Z

Decoy: comments have been solicited, without effective feedback. removing notice of draft status.

== OggPCM ==

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping Headers ====

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type. A compatible implementation of OggPCM channel maps SHOULD support both types of maps, but MAY omit support for the Channel Conversion Header.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined at all, has not been defined for the indicaed version of the header, is not supported by the player, or cannot be rendered accurately, parsing SHOULD continue with the next header.

Encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. It MUST be possible for the user to override any mixing coefficients included by the encoder by default. If no header is found by a decoder which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number, channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_SCREEN_CENTER = 256 = 0x00000100 (ear level, straight ahead, at screen distance)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)
OGG_CHANNEL_FRONT_CENTER = 258 = 0x00000102 (ear level, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite, unless otherwise noted. Hence, the field produced by any speaker feed SHOULD by default approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found in the companion document ''[[channel mapping examples]]''.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affected. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

[[Category:Drafts]]
[[Category:Ogg Mappings]]

OggPCM

2008-10-22T10:40:32Z

Decoy: after waiting for comments and receiving some agreement, elevating option 2 channel mapping headers to the only supported option

== OggPCM ==

The following is an draft format for OggPCM. This is not a final proposal, but has remained reasonably stable for over a year.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping Headers ====

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type. A compatible implementation of OggPCM channel maps SHOULD support both types of maps, but MAY omit support for the Channel Conversion Header.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined at all, has not been defined for the indicaed version of the header, is not supported by the player, or cannot be rendered accurately, parsing SHOULD continue with the next header.

Encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. It MUST be possible for the user to override any mixing coefficients included by the encoder by default. If no header is found by a decoder which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number, channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_SCREEN_CENTER = 256 = 0x00000100 (ear level, straight ahead, at screen distance)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)
OGG_CHANNEL_FRONT_CENTER = 258 = 0x00000102 (ear level, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite, unless otherwise noted. Hence, the field produced by any speaker feed SHOULD by default approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affected. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

[[Category:Drafts]]
[[Category:Ogg Mappings]]

OggPCM

2008-10-22T10:38:26Z

Decoy: /* OggPCM */

== OggPCM ==

The following is an draft format for OggPCM. This is not a final proposal, but has remained reasonably stable for over a year.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type. A compatible implementation of OggPCM channel maps SHOULD support both types of maps, but MAY omit support for the Channel Conversion Header.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined at all, has not been defined for the indicaed version of the header, is not supported by the player, or cannot be rendered accurately, parsing SHOULD continue with the next header.

Encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. It MUST be possible for the user to override any mixing coefficients included by the encoder by default. If no header is found by a decoder which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number, channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_SCREEN_CENTER = 256 = 0x00000100 (ear level, straight ahead, at screen distance)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)
OGG_CHANNEL_FRONT_CENTER = 258 = 0x00000102 (ear level, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite, unless otherwise noted. Hence, the field produced by any speaker feed SHOULD by default approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affected. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

[[Category:Drafts]]
[[Category:Ogg Mappings]]

Channel mapping examples

2008-09-10T14:59:52Z

Decoy: front center semantics

This companion document to the [[OggPCM|OggPCM specification]] lists several examples of possible Channel Mapping and Channel Conversion Headers. They can be used to map most of the currently existing multichannel layouts into OggPCM. This document is INFORMATIVE.

Mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Mapping for Ambisonics G-format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

Mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Mapping for 5.1 in the ITU-R BS.775-1 layout, when a Dolby Surround fallback track is present:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Mapping for ambisonics G+2 format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000005 Channel 5
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000005 Channel 5
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Mapping for Ambisonics G-format, derived for a pentagonal layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000B Channel 11
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000C Channel 12
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x0000000E Channel 14
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x0000000F Channel 15
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

OggPCM

2008-09-10T14:58:21Z

Decoy: the dialogue channel has different semantics from front center

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type. A compatible implementation of OggPCM channel maps SHOULD support both types of maps, but MAY omit support for the Channel Conversion Header.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined at all, has not been defined for the indicaed version of the header, is not supported by the player, or cannot be rendered accurately, parsing SHOULD continue with the next header.

Encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. It MUST be possible for the user to override any mixing coefficients included by the encoder by default. If no header is found by a decoder which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number, channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_SCREEN_CENTER = 256 = 0x00000100 (ear level, straight ahead, at screen distance)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)
OGG_CHANNEL_FRONT_CENTER = 258 = 0x00000102 (ear level, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite, unless otherwise noted. Hence, the field produced by any speaker feed SHOULD by default approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_SCREEN_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_SCREEN_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affected. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

[[Category:Drafts]]
[[Category:Ogg Mappings]]

OggPCM

2007-12-19T12:09:22Z

Decoy: moved comments to discussion page and reverted

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type. A compatible implementation of OggPCM channel maps SHOULD support both types of maps, but MAY omit support for the Channel Conversion Header.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined at all, has not been defined for the indicaed version of the header, is not supported by the player, or cannot be rendered accurately, parsing SHOULD continue with the next header.

Encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. It MUST be possible for the user to override any mixing coefficients included by the encoder by default. If no header is found by a decoder which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number, channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker feed SHOULD approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affected. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

Talk:OggPCM

2007-12-19T12:07:45Z

Decoy: moved comments from the article

Moving these comments from the article for further discussion:

Portable players are usually ARM, which is usually little-endian. The Macintosh is now little-endian. Obviously the PC is little-endian. Clearly there is a winner. It's long past time to stop putting the bytes in an order that makes both programmers and computers do extra work for no good reason. Don't try to hold back the tide.

(the sample rate field) should be a rational with at least a 22-bit numerator and 10-bit denominator

An integer sampling rate is trouble. Audio does not always come that way. For example, audio is sometimes tied to the NTSC frame rate of 30000/1001. That 1001 can show up in the sample rate, and thus needs 10 bits. Rates with a 3 in the denominator are common too. Super Audio CD needs 22 bits to represent 2.8224 MHz. So 22 bits and 10 bits will do the job. Better would be 32 bits for both numerator and denominator of course. A float will never be quite right, though it sure beats an integer and will in fact hold exact values into the MHz. One can't express 1/3 or 1/10 as a float, so 12345.6 and 12345.6666... are undoable that way. BTW, allowing for subsonic recording would be nice.

[[User:Decoy|Decoy]] 04:07, 19 December 2007 (PST)

Perhaps so, but factually people do use OggPCM on big-endian machines. Having big-endian as an option makes sense then, and what is suggested above would then become a recommendation on how to use the format, not a necessary limitation on it.

DSD does not have to be supported, because while technically it can be viewed as high rate PCM, in practice OggPCM aims at supporting the most common forms of conventional PCM, not much more. DSD content is rare, there is no obvious reason why it would be generated by any of the free/open source software projects like Xiph, it would also need its own sample format tag, we would need to go into the specifics of bit packing, and so on. It seems like a whole lot of extra work and complexity for very little gain.

The physical header has already been finalized, so touching the sampling rate parameter is not really an option. Fractional sampling rates would again add complexity for little real benefit, and the option would be difficult to ignore if implemented. That's bad for embedded devices. The point about NTSC, drop-frame and the like is valid, granted, but given how imperfect such sources usually are, addressing the mismatch by simple resampling techniques should be sufficient.

Subsonic recording, that's IMO unnecessary generality for something intended for multimedia work.

[[User:Decoy|Decoy]] 04:07, 19 December 2007 (PST)

OggPCM

2007-11-15T11:10:08Z

Decoy: /* Further Suggestions for Conversion and Rendering */

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type. A compatible implementation of OggPCM channel maps SHOULD support both types of maps, but MAY omit support for the Channel Conversion Header.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined at all, has not been defined for the indicaed version of the header, is not supported by the player, or cannot be rendered accurately, parsing SHOULD continue with the next header.

Encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. It MUST be possible for the user to override any mixing coefficients included by the encoder by default. If no header is found by a decoder which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number, channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker feed SHOULD approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affected. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

OggPCM

2007-11-15T11:07:29Z

Decoy: /* Channel Mapping, proposed option 2 */

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type. A compatible implementation of OggPCM channel maps SHOULD support both types of maps, but MAY omit support for the Channel Conversion Header.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined at all, has not been defined for the indicaed version of the header, is not supported by the player, or cannot be rendered accurately, parsing SHOULD continue with the next header.

Encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. It MUST be possible for the user to override any mixing coefficients included by the encoder by default. If no header is found by a decoder which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number, channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker feed SHOULD approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affeced. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

OggPCM

2007-11-15T10:41:06Z

Decoy: /* External Links */

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker feed SHOULD approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot and in average they MUST be temporally aligned with the rest of the channels.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affeced. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]
*[http://www.acoustics.hut.fi/research/cat/vbap/ Vector Base Amplitude Panning]

OggPCM

2007-11-15T10:40:35Z

Decoy: /* Further Suggestions for Conversion and Rendering */

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker feed SHOULD approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot and in average they MUST be temporally aligned with the rest of the channels.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

When speakers are available all around the position of the desired feed, and they subtend no more than a typical stereo pair (60 degrees), a common simulation of a feed is to apply an equal power panning law among the closest two or three speakers. This is also what is done in the default mappings from the central channels to the stereo pair. In three dimensions this approach leads to Vector Base Amplitude Panning (VBAP).

Another possibility is to pan the speaker feed into an Ambisonics representation of some chosen order, and then to decode for the actual speaker layout.

When speakers to the back are not available, the respective speaker feeds are often mixed to opposite speakers in the front. The default mappings do this for stereo, and apply a 3dB attenuation to the back. The latter convention derives from European Broadcasting Union downmixing guidelines, and Dolby AC-3 defaults.

If speakers close to the desired positions are available, the speaker feed can also be routed directly to one of them, as long as the overall directional errors stay limited and the relative ordering of the channels is not affeced. The channel maps and channel numbering are aimed at helping such mappings in existing systems: when the mapping examples in this document and the companion one are applied, in most cases channel ordering becomes identical to that used in WAV files and USB serializations. Rounding the channels to the positions specified in the respective channel masks should then lead to a workable rendering.

OggPCM encoders are encouraged to supply downmixing information for common output formats, but it is to be expected that the information will often be incomplete. In such cases, the mapping examples given in this document and the companion can be applied by default by the decoder when the stored signal set seems to fit one of them.

Proper downmixing to certain output formats, like Dolby Surround and Ambisonics UHJ, require complex processing which cannot be specified using a simple downmix matrix. If such output options are available, proper transcoding can be attempted as soon as the first channel map has been found which specifies a set of channels amenable to such a representation. The same goes for binaural rendering and is extensions, like crosstalk cancellation, which utilize head related transfer functions (HRTF) for accurate spatial rendering over a limited number of channels.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]

OggPCM

2007-11-15T10:12:14Z

Decoy: /* Defaulting and Standard Mappings */

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker feed SHOULD approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot and in average they MUST be temporally aligned with the rest of the channels.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.
* Files containing some other number of channels and no explicit channel map are assumed to contain channels tagged with OGG_CHANNEL_UNUSED

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]

OggPCM

2007-11-15T10:03:50Z

Decoy: stereo and mono conversions for the rest of the default layouts

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping Header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, encoders SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate rendering MAY be attempted, as outlined in the section on conversions and rendering below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. However, if more than one channel is tagged as OGG_CHANNEL_UNUSED, they are all considered unused and shouldn't be played. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

// specials
OGG_CHANNEL_UNUSED = 2816 = 0x00000B00 (the channel is unused and should not be rendered)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker feed SHOULD approximate a planar wave at the sweet spot.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Channel_types marked as being "diffuse" are intended to be reproduced in a spatially dispersed manner, from and around the indicated direction. As two common examples, they might be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot and in average they MUST be temporally aligned with the rest of the channels.

===== Defaulting and Standard Mappings =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion Headers that are implied are specified below. Further INFORMATIVE mappings for various channel layouts can be found [[channel mapping examples|in a companion document]].

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_AMBISONICS_X
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_AMBISONICS_Y
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0xFFFF4AFC Mixing coefficient -1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_AMBISONICS_W
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00016A09 Mixing coefficient sqrt(2)

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 6.1 in the ITU+back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00008000 Mixing coefficient 1/2

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_BACK_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00010000 Mixing coefficient 1
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00010000 Mixing coefficient 1
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00071231 Mixing coefficient 10/sqrt(2)
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000D744 Mixing coefficient 1/sqrt(sqrt(2))

32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000002 Channel 2, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00010000 Mixing coefficient 1
32 0x00000003 Channel 3, containing OGG_CHANNEL_LFE
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x000A0000 Mixing coefficient 10
32 0x00000004 Channel 4, containing OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000005 Channel 5, containing OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00008000 Mixing coefficient 1/2
32 0x00000006 Channel 6, containing OGG_CHANNEL_SIDE_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000007 Channel 7, containing OGG_CHANNEL_SIDE_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. This section outlines some strategies which MAY be used in approximate rendering.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]
*[http://developer.apple.com/documentation/MusicAudio/Reference/CAFSpec/CAF_intro/chapter_1_section_1.html#//apple_ref/doc/uid/TP40001862-CH203-DontLinkElementID_60 Apple Core Audio Format 1.0 specification]

Channel mapping examples

2007-11-15T09:22:08Z

Decoy: let's just take the basic 10.2, because data on the extended version is scarce

This companion document to the [[OggPCM|OggPCM specification]] lists several examples of possible Channel Mapping and Channel Conversion Headers. They can be used to map most of the currently existing multichannel layouts into OggPCM. This document is INFORMATIVE.

Mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Mapping for Ambisonics G-format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

Mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Mapping for 5.1 in the ITU-R BS.775-1 layout, when a Dolby Surround fallback track is present:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Mapping for ambisonics G+2 format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000005 Channel 5
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000005 Channel 5
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Mapping for Ambisonics G-format, derived for a pentagonal layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000B Channel 11
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000C Channel 12
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x0000000E Channel 14
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x0000000F Channel 15
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

OggPCM

2007-11-15T09:15:31Z

Decoy: added default mapping headers, lightened the language some, added OGG_CHANNEL_UNUSED

OggPCM

2007-11-14T20:40:14Z

Decoy: /* Further Suggestions for Conversion and Rendering */

OggPCM

2007-11-14T17:23:38Z

Decoy: /* Further Suggestions for Conversion and Rendering */

OggPCM

2007-11-14T17:16:09Z

Decoy: added lnk to caf spec

Channel mapping examples

2007-11-14T17:13:52Z

Decoy: the mappings are no longer defaults, just informative examples

This companion document to the [[OggPCM|OggPCM specification]] lists several examples of possible Channel Mapping and Channel Conversion Headers. They can be used to map most of the currently existing multichannel layouts into OggPCM. This document is INFORMATIVE.

Mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Mapping for Ambisonics G-format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

Mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Mapping for 5.1 in the ITU-R BS.775-1 layout, when a Dolby Surround fallback track is present:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Mapping for ambisonics G+2 format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000005 Channel 5
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000005 Channel 5
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Mapping for Ambisonics G-format, derived for a pentagonal layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

Channel mapping examples

2007-11-14T17:12:10Z

Decoy: added ambisonics G+2, and G-format for square layout

This companion document to the [[OggPCM|OggPCM specification]] lists several examples of possible Channel Mapping and Channel Conversion Headers. They can be used to map most of the currently existing multichannel layouts into OggPCM. This document is INFORMATIVE.

Default mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Default mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Default mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Default mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Default mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for Ambisonics G-format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

Default mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Default mapping for 5.1 in the ITU-R BS.775-1 layout, when a Dolby Surround fallback track is present:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for ambisonics G+2 format, derived for a square layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00004000 Mixing coefficient 0.25
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00005A82 Mixing coefficient 0.25*sqrt(2)
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFA57E Mixing coefficient -0.25*sqrt(2)

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000005 Channel 5
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000004 Channel 4
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000005 Channel 5
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for Ambisonics G-format, derived for a pentagonal layout using the energy decoding equation:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00003333 Mixing coefficient 0.2
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Default mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Default mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

Channel mapping examples

2007-11-14T16:56:46Z

Decoy: moved most of the mapping examples from oggpcm, and made them INFORMATIVE

This companion document to the [[OggPCM|OggPCM specification]] lists several examples of possible Channel Mapping and Channel Conversion Headers. They can be used to map most of the currently existing multichannel layouts into OggPCM. This document is INFORMATIVE.

Default mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Default mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Default mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Default mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Default mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for Ambisonics G-format:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L, redundant and only present in G+2 format
32 0x00000006 Channel 6
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R, redundant and only present in G+2 format

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000006 Channel 6
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Default mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Default mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

OggPCM

2007-11-14T16:51:42Z

Decoy: separated the example mappings into a companion document

OggPCM

2007-11-13T17:49:42Z

Decoy: removed duplicate mapping

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Unless otherwise indicated, channel_types marked as being "diffuse" are intended to be reproduced with an average cardioid response emanating from the stated direction. They MAY instead be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or they MAY be reproduced by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot, in average they MUST be temporally aligned with the rest of the channels at the sweet spot, at each frequency they SHOULD be reproduced with maximal spatial dispersion consistent with the above, and each pair of diffuse channels SHOULD be temporally decorrelated to the maximum degree that is consistent with the above.

===== Defaulting =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.

===== Standard Mappings =====

The OggPCM channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below.

Because there is more variability in the source standards than in the OggPCM specification, different mappings might sometimes be needed. That is why most of this list is to be considered INFORMATIVE. However, the mappings referred to by the section on defaulting, above, are to be considered NORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Default mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Default mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Default mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 6.1 in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics G-format:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L, redundant and only present in G+2 format
32 0x00000006 Channel 6
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R, redundant and only present in G+2 format

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000006 Channel 6
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Default mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Default mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

===== Standard Conversions =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also to support rudimentary downmixing into many different layouts. In the following a set of Channel Conversion Headers are provided which MAY be applied by default.

If this is done, these headers should be considered as having lower priority than any header explicitly provided by the OggPCM stream. That is, if they are incorporated by the decoder, they MUST be added after the last header provided by the OggPCM stream itself.

If they are instead incorporated by the OggPCM encoder, they MUST be fully controllable by the user. Furthermore, the mixing functionality of Channel Conversion Headers MUST NOT be used to override the semantics of defined channel_types.

Default conversion from plain stereo to plain mono:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default conversion from plain mono to plain stereo:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even when extensive downmixing information is present, it might not cover the precise speaker layout or hardware capabilities needed for precise playback. That is why this INFORMATIVE section gives some extra tips on channel mapping which cannot be expressed using Channel Conversion Headers.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]

OggPCM

2007-11-12T12:58:58Z

Decoy: diffuseness is better explained via pairwise decorrelation

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Unless otherwise indicated, channel_types marked as being "diffuse" are intended to be reproduced with an average cardioid response emanating from the stated direction. They MAY instead be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or they MAY be reproduced by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot, in average they MUST be temporally aligned with the rest of the channels at the sweet spot, at each frequency they SHOULD be reproduced with maximal spatial dispersion consistent with the above, and each pair of diffuse channels SHOULD be temporally decorrelated to the maximum degree that is consistent with the above.

===== Defaulting =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.

===== Standard Mappings =====

The OggPCM channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below.

Because there is more variability in the source standards than in the OggPCM specification, different mappings might sometimes be needed. That is why most of this list is to be considered INFORMATIVE. However, the mappings referred to by the section on defaulting, above, are to be considered NORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Default mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Default mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Default mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 6.1 in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics G-format:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L, redundant and only present in G+2 format
32 0x00000006 Channel 6
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R, redundant and only present in G+2 format

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000006 Channel 6
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Default mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Default mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

===== Standard Conversions =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also to support rudimentary downmixing into many different layouts. In the following a set of Channel Conversion Headers are provided which MAY be applied by default.

If this is done, these headers should be considered as having lower priority than any header explicitly provided by the OggPCM stream. That is, if they are incorporated by the decoder, they MUST be added after the last header provided by the OggPCM stream itself.

If they are instead incorporated by the OggPCM encoder, they MUST be fully controllable by the user. Furthermore, the mixing functionality of Channel Conversion Headers MUST NOT be used to override the semantics of defined channel_types.

Default conversion from plain stereo to plain mono:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default conversion from plain mono to plain stereo:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even when extensive downmixing information is present, it might not cover the precise speaker layout or hardware capabilities needed for precise playback. That is why this INFORMATIVE section gives some extra tips on channel mapping which cannot be expressed using Channel Conversion Headers.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]

OggPCM

2007-11-12T12:53:29Z

Decoy: blumlein and xy seem to be different after all

== OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, option 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed option 2 ====

This proposed version of Channel Mapping has not yet gained the support of the Xiph.Org Foundation. However, it is likely the more mature proposal between the two. Still needs a bit more of polish, though.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_BLUMLEIN_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_BLUMLEIN_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_XY_LEFT = 20 = 0x00000014 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 21 = 0x00000015 (cardioid response 45 degrees to the right)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Unless otherwise indicated, channel_types marked as being "diffuse" are intended to be reproduced with an average cardioid response emanating from the stated direction. They MAY instead be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or they MAY be reproduced by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot, in average they MUST be temporally aligned with the rest of the channels at the sweet spot, at each frequency they SHOULD be reproduced with maximal spatial dispersion consistent with the above, and they SHOULD be reproduced with maximal phase delay variation consistent with the above, and with the psychoacoustics of maximally reverberant sound arriving from the stated principal direction.

===== Defaulting =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.

===== Standard Mappings =====

The OggPCM channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below.

Because there is more variability in the source standards than in the OggPCM specification, different mappings might sometimes be needed. That is why most of this list is to be considered INFORMATIVE. However, the mappings referred to by the section on defaulting, above, are to be considered NORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Default mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Default mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Default mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 6.1 in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics G-format:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L, redundant and only present in G+2 format
32 0x00000006 Channel 6
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R, redundant and only present in G+2 format

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000006 Channel 6
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Default mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Default mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

===== Standard Conversions =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also to support rudimentary downmixing into many different layouts. In the following a set of Channel Conversion Headers are provided which MAY be applied by default.

If this is done, these headers should be considered as having lower priority than any header explicitly provided by the OggPCM stream. That is, if they are incorporated by the decoder, they MUST be added after the last header provided by the OggPCM stream itself.

If they are instead incorporated by the OggPCM encoder, they MUST be fully controllable by the user. Furthermore, the mixing functionality of Channel Conversion Headers MUST NOT be used to override the semantics of defined channel_types.

Default conversion from plain stereo to plain mono:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default conversion from plain mono to plain stereo:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even when extensive downmixing information is present, it might not cover the precise speaker layout or hardware capabilities needed for precise playback. That is why this INFORMATIVE section gives some extra tips on channel mapping which cannot be expressed using Channel Conversion Headers.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]

OggPCM

2007-10-24T16:29:55Z

Decoy: killed uhj_sigma, uhj_delta, and regular matrix, changed XY to figure of eights /* Channel Mapping, proposed draft 2 */

'''This page was created as an alternative to the original [[OggPCM Draft1]]. After a [http://lists.xiph.org/pipermail/ogg-dev/2005-November/thread.html heated debate] most developers are now working on this version of the spec.'''

== Draft format 2 for OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, draft 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed draft 2 ====

This proposal has not yet gained the support of the Xiph community. It should be considered EXPERIMENTAL.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_XY_LEFT = 4 = 0x00000004 (figure of eight response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 5 = 0x00000005 (figure of eight response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Unless otherwise indicated, channel_types marked as being "diffuse" are intended to be reproduced with an average cardioid response emanating from the stated direction. They MAY instead be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or they MAY be reproduced by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot, in average they MUST be temporally aligned with the rest of the channels at the sweet spot, at each frequency they SHOULD be reproduced with maximal spatial dispersion consistent with the above, and they SHOULD be reproduced with maximal phase delay variation consistent with the above, and with the psychoacoustics of maximally reverberant sound arriving from the stated principal direction.

===== Defaulting =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.

===== Standard Mappings =====

The OggPCM channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below.

Because there is more variability in the source standards than in the OggPCM specification, different mappings might sometimes be needed. That is why most of this list is to be considered INFORMATIVE. However, the mappings referred to by the section on defaulting, above, are to be considered NORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Default mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Default mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Default mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 6.1 in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics G-format:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L, redundant and only present in G+2 format
32 0x00000006 Channel 6
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R, redundant and only present in G+2 format

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000006 Channel 6
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Default mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Default mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

===== Standard Conversions =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also to support rudimentary downmixing into many different layouts. In the following a set of Channel Conversion Headers are provided which MAY be applied by default.

If this is done, these headers should be considered as having lower priority than any header explicitly provided by the OggPCM stream. That is, if they are incorporated by the decoder, they MUST be added after the last header provided by the OggPCM stream itself.

If they are instead incorporated by the OggPCM encoder, they MUST be fully controllable by the user. Furthermore, the mixing functionality of Channel Conversion Headers MUST NOT be used to override the semantics of defined channel_types.

Default conversion from plain stereo to plain mono:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default conversion from plain mono to plain stereo:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even when extensive downmixing information is present, it might not cover the precise speaker layout or hardware capabilities needed for precise playback. That is why this INFORMATIVE section gives some extra tips on channel mapping which cannot be expressed using Channel Conversion Headers.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]

OggPCM

2007-10-24T14:46:35Z

Decoy: renumbered the channels, added standard mappings for most extant systems /* Channel Mapping, proposed draft 2 */

'''This page was created as an alternative to the original [[OggPCM Draft1]]. After a [http://lists.xiph.org/pipermail/ogg-dev/2005-November/thread.html heated debate] most developers are now working on this version of the spec.'''

== Draft format 2 for OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and Ambisonic signals.

==== Channel Mapping, draft 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format Ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed draft 2 ====

This proposal has not yet gained the support of the Xiph community. It should be considered EXPERIMENTAL.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used.

A header is considered to be present once its header ID has been read successfully. If a field or structure is prematurely terminated after reading the ID, the header is considered erroneous. If an error is encountered in a header, it MUST be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels MUST be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use, but they MUST NOT be considered an error.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type which has not been defined is encountered, this MUST be considered an error. If a channel_type is encountered which is defined only for a newer version of the header than indicated, this MAY be considered an error, in which case parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the decoder, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the decoder, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, the first associated channel_type MUST be used. If a channel_type is present more than once in a Channel Mapping Header, the first associated channel number MUST be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, the first mixing coefficient for the pair MUST be used. If channel mapping data is neglected because of these rules, readers SHOULD still accept the header without treating it as an error, but MAY warn the user.

The mixing coefficients are 32 bit signed, two's complement, fixed point numbers. The 16 most significant bits contain the integer part (including sign), and the 16 least significant bits are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined. They are divided into groups corresponding to the closest mapping into the set of channels used in CAF, RIFF WAVE and USB channel masks:

// front left/right
OGG_CHANNEL_STEREO_LEFT = 0 = 0x00000000 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 1 = 0x00000001 (30 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 2 = 0x00000002 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 3 = 0x00000003 (45 degrees right)
OGG_CHANNEL_XY_LEFT = 4 = 0x00000004 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_RIGHT = 5 = 0x00000005 (cardioid response 45 degrees to the right)
OGG_CHANNEL_WALL_FRONT_LEFT = 6 = 0x00000006 (55 degrees left)
OGG_CHANNEL_WALL_FRONT_RIGHT = 7 = 0x00000007 (55 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 8 = 0x00000008 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 9 = 0x00000009 (60 degrees right)
OGG_CHANNEL_PENTAGONAL_FRONT_LEFT = 10 = 0x0000000A (72 degrees left)
OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT = 11 = 0x0000000B (72 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 12 = 0x0000000C (fed directly into the left ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_BINAURAL_RIGHT = 13 = 0x0000000D (fed directly into the right ear canal, or front stereo dipole with crosstalk cancellation)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 14 = 0x0000000E (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 15 = 0x0000000F (5 degrees right)
OGG_CHANNEL_UHJ_L = 16 = 0x00000010 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 17 = 0x00000011 (ambisonics UHJ right)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 18 = 0x00000012 (dolby stereo/surround left total)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 19 = 0x00000013 (dolby stereo/surround right total)
OGG_CHANNEL_REGULAR_MATRIX_LEFT = 20 = 0x00000014 (regular matrix left total)
OGG_CHANNEL_REGULAR_MATRIX_RIGHT = 21 = 0x00000015 (regular matrix right total)

// front center/mono
OGG_CHANNEL_FRONT_CENTER = 256 = 0x00000100 (ear level, straight ahead)
OGG_CHANNEL_MS_MID = 257 = 0x00000101 (cardioid response, straight ahead)
OGG_CHANNEL_UHJ_SIGMA = 258 = 0x00000102 (ambisonics UHJ mono/sum/mid)

// lfe
OGG_CHANNEL_LFE = 512 = 0x00000200 (omnidirectional, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_LEFT = 513 = 0x00000201 (90 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_SIDE_RIGHT = 514 = 0x00000202 (90 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_LEFT = 515 = 0x00000203 (22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT = 516 = 0x00000204 (22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT = 517 = 0x00000205 (45 degrees lowered, 22.5 degrees left, bandlimited to 120Hz, 10dB louder than the reference level)
OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT = 518 = 0x00000206 (45 degrees lowered, 22.5 degrees right, bandlimited to 120Hz, 10dB louder than the reference level)

// back left/right
OGG_CHANNEL_ITU_BACK_LEFT = 768 = 0x00000300 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 769 = 0x00000301 (back, 70 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT_SURROUND = 770 = 0x00000302 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND = 771 = 0x00000303 (back, 70 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 772 = 0x00000304 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 773 = 0x00000305 (back, 60 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 774 = 0x00000306 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 775 = 0x00000307 (back, 45 degrees right)
OGG_CHANNEL_PENTAGONAL_BACK_LEFT = 776 = 0x00000308 (back, 36 degrees left)
OGG_CHANNEL_PENTAGONAL_BACK_RIGHT = 777 = 0x00000309 (back, 36 degrees right)
OGG_CHANNEL_BACK_STEREO_LEFT = 778 = 0x0000030A (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 779 = 0x0000030B (back, 30 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 780 = 0x0000030C (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 781 = 0x0000020E (back, 5 degrees right)

// front center left/right
OGG_CHANNEL_FRONT_CENTER_LEFT = 1024 = 0x00000400 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 1025 = 0x00000401 (22.5 degrees right)

// back center
OGG_CHANNEL_BACK_CENTER = 1280 = 0x00000500 (straight back)
OGG_CHANNEL_BACK_CENTER_SURROUND = 1281 = 0x00000501 (straight back, diffuse)
OGG_CHANNEL_SURROUND = 1282 = 0x00000502 (back and sides, diffuse)

// side left/right
OGG_CHANNEL_SIDE_LEFT = 1536 = 0x00000600 (90 degrees left)
OGG_CHANNEL_SIDE_RIGHT = 1537 = 0x00000601 (90 degrees right)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 1538 = 0x00000602 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 1539 = 0x00000603 (90 degrees right, diffuse)

// rest of the wav/usb/caf mask types
OGG_CHANNEL_TOP_CENTER = 1792 = 0x00000700 (90 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 1793 = 0x00000701 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_CENTER = 1794 = 0x00000702 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_RIGHT = 1795 = 0x00000703 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_LEFT = 1796 = 0x00000704 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 1797 = 0x00000705 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_RIGHT = 1798 = 0x00000706 (back, 45 degrees elevated, 45 degrees right)

// rest of the cube
OGG_CHANNEL_SIDE_TOP_LEFT = 2048 = 0x00000800 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP_RIGHT = 2049 = 0x00000801 (45 degrees elevated, 90 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 2050 = 0x00000802 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 2051 = 0x00000803 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 2052 = 0x00000804 (45 degrees lowered, 45 degrees right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 2053 = 0x00000805 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BOTTOM_CENTER = 2054 = 0x00000806 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 2055 = 0x00000807 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 2056 = 0x00000808 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 2057 = 0x00000809 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 2058 = 0x0000080A (back, 45 degrees lowered, 45 degrees right)

// ambisonics
OGG_CHANNEL_AMBISONICS_W = 2304 = 0x00000900 (0th order)
OGG_CHANNEL_AMBISONICS_X = 2305 = 0x00000901 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 2306 = 0x00000902 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 2307 = 0x00000903 (1st order)
OGG_CHANNEL_AMBISONICS_R = 2308 = 0x00000904 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 2309 = 0x00000905 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 2310 = 0x00000906 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 2311 = 0x00000907 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 2312 = 0x00000908 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 2313 = 0x00000909 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 2314 = 0x0000090A (3rd order)
OGG_CHANNEL_AMBISONICS_M = 2315 = 0x0000090B (3rd order)
OGG_CHANNEL_AMBISONICS_N = 2316 = 0x0000090C (3rd order)
OGG_CHANNEL_AMBISONICS_O = 2317 = 0x0000090D (3rd order)
OGG_CHANNEL_AMBISONICS_P = 2318 = 0x0000090E (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 2319 = 0x0000090F (3rd order)

// passive matrix additions
OGG_CHANNEL_MS_SIDE = 2306 = 0x00000902 (figure of eight response left to right, same as Ambisonics Y)
OGG_CHANNEL_UHJ_DELTA = 2560 = 0x00000A00 (ambisonics UHJ side/difference)
OGG_CHANNEL_UHJ_T = 2561 = 0x00000A01 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 2562 = 0x00000A02 (ambisonics UHJ addition for periphony)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

Unless otherwise indicated, each channel should give rise to the same sound pressure level at the listener. The channel mapping metadata does not impose an absolute reference level for the channel data. The relative levels for ambisonic channels are given by the Furse-Malham convention.

Unless otherwise indicated, channel_types marked as being "diffuse" are intended to be reproduced with an average cardioid response emanating from the stated direction. They MAY instead be reproduced using dipole speakers aligned so that direct arrival of sound to the sweet spot is minimized, or they MAY be reproduced by multiple speakers placed slightly above the listener in and around the stated direction. They SHOULD retain flat average spectral response as measured from the sweet spot, in average they MUST be temporally aligned with the rest of the channels at the sweet spot, at each frequency they SHOULD be reproduced with maximal spatial dispersion consistent with the above, and they SHOULD be reproduced with maximal phase delay variation consistent with the above, and with the psychoacoustics of maximally reverberant sound arriving from the stated principal direction.

===== Defaulting =====

OggPCM streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order pantophonic Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order periphonic Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 in the ITU+back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 in the Dolby/DTS discrete layout.

===== Standard Mappings =====

The OggPCM channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below.

Because there is more variability in the source standards than in the OggPCM specification, different mappings might sometimes be needed. That is why most of this list is to be considered INFORMATIVE. However, the mappings referred to by the section on defaulting, above, are to be considered NORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for stereo with headphone rendering intent:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000C Channel_type OGG_CHANNEL_BINAURAL_LEFT
32 0x00000001 Channel 1
32 0x0000000D Channel_type OGG_CHANNEL_BINAURAL_RIGHT

Default mapping for two channel ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L
32 0x00000001 Channel 1
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R

Default mapping for mono compatible ambisonics UHJ:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000102 Channel_type OGG_CHANNEL_UHJ_SIGMA
32 0x00000001 Channel 1
32 0x00000A00 Channel_type OGG_CHANNEL_UHJ_DELTA

Default mapping for mid/side stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000101 Channel_type OGG_CHANNEL_MS_MID
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_MS_SIDE

Default mapping for Dolby MP matrix stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT

Default mapping for first order pantophonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y

Default mapping for first order periphonic Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for horizontal quadraphony in the diagonal layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for horizontal quadraphony in the diamond layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000002 Channel 2
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000003 Channel 3
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 4.1:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT

Default mapping for Dolby format 42 ("baby boom") 4.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000203 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000204 Channel_type OGG_CHANNEL_LFE_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for 5.0 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for horizontal pentaphony:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

Default mapping for 5.1 in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000012 Channel_type OGG_CHANNEL_DOLBY_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000013 Channel_type OGG_CHANNEL_DOLBY_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT, redundant, used to signal the presence of a stereo fallback mix
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT, redundant, used to signal the presence of a stereo fallback mix

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 5.1 in the layout suggested by THX mastering guidelines:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000005 Channel 5
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 6.0 in the Dolby format 40 layout, used with 70mm film:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000502 Channel_type OGG_CHANNEL_SURROUND

Default mapping for horizontal hexagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000008 Channel_type OGG_CHANNEL_HEX_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000009 Channel_type OGG_CHANNEL_HEX_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000304 Channel_type OGG_CHANNEL_HEX_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000305 Channel_type OGG_CHANNEL_HEX_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics B+format:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000005 Channel 5
32 0x00000903 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 6.1 in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for Ambisonics G-format:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000001 Channel 1
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000002 Channel 2
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000003 Channel 3
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000004 Channel 4
32 0x00000900 Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00002434 Mixing coefficient 0.2*1/sqrt(2)
32 0x00000000 Channel 0
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000001 Channel 1
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000002 Channel 2
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x0000CCCC Mixing coefficient 0.8
32 0x00000003 Channel 3
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000004 Channel 4
32 0x00000901 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0xFFFFCCCD Mixing coefficient -0.2
32 0x00000000 Channel 0
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x0000434B Mixing coefficient 1/(4sin(2pi/5))
32 0x00000001 Channel 1
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFFBCB5 Mixing coefficient 1/(4sin(-2pi/5))
32 0x00000003 Channel 3
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00006CE2 Mixing coefficient 1/(4sin(2pi/10))
32 0x00000004 Channel 4
32 0x00000902 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0xFFFF931E Mixing coefficient 1/(4sin(-2pi/10))

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000000A Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_LEFT
32 0x00000001 Channel 1
32 0x0000000B Channel_type OGG_CHANNEL_PENTAGONAL_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000308 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000309 Channel_type OGG_CHANNEL_PENTAGONAL_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000010 Channel_type OGG_CHANNEL_UHJ_L, redundant and only present in G+2 format
32 0x00000006 Channel 6
32 0x00000011 Channel_type OGG_CHANNEL_UHJ_R, redundant and only present in G+2 format

32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000005 Channel 5
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000006 Channel 6
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for 7.1 in the Dolby/DTS discrete layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000030A Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000005 Channel 5
32 0x0000030B Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for 7.1 in the THX Advanced Speaker Array (ASA) layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel 1
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000002 Channel 2
32 0x0000030C Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT
32 0x00000003 Channel 3
32 0x0000030D Channel_type OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for 7.1 in the SDDS layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000200 Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000005 Channel 5
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000006 Channel 6
32 0x00000602 Channel_type OGG_CHANNEL_SIDE_LEFT_SURROUND
32 0x00000007 Channel 7
32 0x00000603 Channel_type OGG_CHANNEL_SIDE_RIGHT_SURROUND

Default mapping for the CAF cubical layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000003 Channel 3
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000004 Channel 4
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x00000005 Channel 5
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000006 Channel 6
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000007 Channel 7
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT

Default mapping for horizontal octagonal:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000004 Channel 4
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000005 Channel 5
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x00000006 Channel 6
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000007 Channel 7
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT

Default mapping for TMH 10.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000201 Channel_type OGG_CHANNEL_LFE_SIDE_LEFT
32 0x00000004 Channel 4
32 0x00000202 Channel_type OGG_CHANNEL_LFE_SIDE_RIGHT
32 0x00000005 Channel 5
32 0x00000300 Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000301 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000302 Channel_type OGG_CHANNEL_ITU_BACK_LEFT_SURROUND
32 0x00000008 Channel 8
32 0x00000303 Channel_type OGG_CHANNEL_ITU_BACK_RIGHT_SURROUND
32 0x00000009 Channel 9
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT, only present in extended configuration
32 0x0000000A Channel 10
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT, only present in extended configuration
32 0x0000000B Channel 11
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000C Channel 12
32 0x00000501 Channel_type OGG_CHANNEL_BACK_CENTER_SURROUND
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000006 Channel_type OGG_CHANNEL_WALL_FRONT_LEFT
32 0x00000011 Channel 17
32 0x00000007 Channel_type OGG_CHANNEL_WALL_FRONT_RIGHT

Default mapping for Hamasaki 22.2:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000002 Channel_type OGG_CHANNEL_QUAD_FRONT_LEFT
32 0x00000001 Channel 1
32 0x00000003 Channel_type OGG_CHANNEL_QUAD_FRONT_RIGHT
32 0x00000002 Channel 2
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x00000205 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_LEFT
32 0x00000004 Channel 4
32 0x00000206 Channel_type OGG_CHANNEL_LFE_FRONT_BOTTOM_CENTER_RIGHT
32 0x00000005 Channel 5
32 0x00000306 Channel_type OGG_CHANNEL_QUAD_BACK_LEFT
32 0x00000006 Channel 6
32 0x00000307 Channel_type OGG_CHANNEL_QUAD_BACK_RIGHT
32 0x00000007 Channel 7
32 0x00000400 Channel_type OGG_CHANNEL_FRONT_CENTER_LEFT
32 0x00000008 Channel 8
32 0x00000401 Channel_type OGG_CHANNEL_FRONT_CENTER_RIGHT
32 0x00000009 Channel 9
32 0x00000500 Channel_type OGG_CHANNEL_BACK_CENTER
32 0x0000000A Channel 10
32 0x00000600 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x0000000B Channel 11
32 0x00000601 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x0000000C Channel 12
32 0x00000700 Channel_type OGG_CHANNEL_TOP_CENTER
32 0x0000000D Channel 13
32 0x00000701 Channel_type OGG_CHANNEL_FRONT_TOP_LEFT
32 0x0000000E Channel 14
32 0x00000702 Channel_type OGG_CHANNEL_FRONT_TOP_CENTER
32 0x0000000F Channel 15
32 0x00000703 Channel_type OGG_CHANNEL_FRONT_TOP_RIGHT
32 0x00000010 Channel 16
32 0x00000704 Channel_type OGG_CHANNEL_BACK_TOP_LEFT
32 0x00000011 Channel 17
32 0x00000705 Channel_type OGG_CHANNEL_BACK_TOP_CENTER
32 0x00000012 Channel 18
32 0x00000706 Channel_type OGG_CHANNEL_BACK_TOP_RIGHT
32 0x00000013 Channel 19
32 0x00000800 Channel_type OGG_CHANNEL_SIDE_TOP_LEFT
32 0x00000014 Channel 20
32 0x00000801 Channel_type OGG_CHANNEL_SIDE_TOP_RIGHT
32 0x00000015 Channel 21
32 0x00000802 Channel_type OGG_CHANNEL_FRONT_BOTTOM_LEFT
32 0x00000016 Channel 22
32 0x00000803 Channel_type OGG_CHANNEL_FRONT_BOTTOM_CENTER
32 0x00000017 Channel 23
32 0x00000804 Channel_type OGG_CHANNEL_FRONT_BOTTOM_RIGHT

===== Standard Conversions =====

Even if a decoder supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also to support rudimentary downmixing into many different layouts. In the following a set of Channel Conversion Headers are provided which MAY be applied by default.

If this is done, these headers should be considered as having lower priority than any header explicitly provided by the OggPCM stream. That is, if they are incorporated by the decoder, they MUST be added after the last header provided by the OggPCM stream itself.

If they are instead incorporated by the OggPCM encoder, they MUST be fully controllable by the user. Furthermore, the mixing functionality of Channel Conversion Headers MUST NOT be used to override the semantics of defined channel_types.

Default conversion from plain stereo to plain mono:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_STEREO_LEFT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000001 Channel 1, containing OGG_CHANNEL_STEREO_RIGHT
32 0x00000100 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x0000B504 Mixing coefficient 1/sqrt(2)

Default conversion from plain mono to plain stereo:
32 0x00000001 Channel Conversion Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000000 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x0000B504 Mixing coefficient 1/sqrt(2)
32 0x00000000 Channel 0, containing OGG_CHANNEL_FRONT_CENTER
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x0000B504 Mixing coefficient 1/sqrt(2)

===== Further Suggestions for Conversion and Rendering =====

Even when extensive downmixing information is present, it might not cover the precise speaker layout or hardware capabilities needed for precise playback. That is why this INFORMATIVE section gives some extra tips on channel mapping which cannot be expressed using Channel Conversion Headers.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]

OggPCM

2007-10-22T11:50:34Z

Decoy: since OggPCM now redirects here and the {{draft}} tag had been removed there, I removed it from here as well

'''This page was created as an alternative to the original [[OggPCM_Draft1]]. After a [http://lists.xiph.org/pipermail/ogg-dev/2005-November/thread.html heated debate] most developers are now working on this version of the spec.'''

== Draft format 2 for OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and ambisonics signals.

==== Channel Mapping, draft 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADRAPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing three channels are assumed to be B-format ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y

* Files containing four channels are assumed to be B-format ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to a mono file by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to a mono file using Mono = W*sqrt(2).
* Ambisonic files SHOULD be converted to stereo files by dematrixing W, X and Y.

==== Channel Mapping, proposed draft 2 ====

This proposal has not yet gained the support of the Xiph community. It should be considered EXPERIMENTAL.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM2 stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used. If an error is encountered in one of the headers, the header SHOULD be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM2 stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels SHOULD be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type is encountered which is not defined for the given version of the mapping header, this SHOULD be considered an error and parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the player, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the player, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, only the first associated channel_type SHOULD be used. If a channel_type is present more than once in a Channel Mapping Header, only the first associated channel number SHOULD be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, only the first mixing coefficient for the pair SHOULD be used. Readers SHOULD still accept the header without treating it as an error, but SHOULD warn the user.

The mixing coefficients are 32 bit signed, fixed point numbers. The 16 most significant bits are the integer part (including sign), and 16 least significant parts are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined:

OGG_CHANNEL_FRONT_CENTER = 0 (ear level, straight ahead)
OGG_CHANNEL_STEREO_LEFT = 1 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 2 (30 degrees right)
OGG_CHANNEL_FRONT_CENTER_LEFT = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 4 (22.5 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 5 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 6 (45 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 7 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 8 (back, 45 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 9 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 10 (60 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 11 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 12 (back, 60 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT = 13 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 14 (back, 70 degrees right)
OGG_CHANNEL_FRONT_TOP_CENTER = 15 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 16 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_RIGHT = 17 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 18 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 19 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 20 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_SIDE_TOP_LEFT = 21 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP = 22 (90 degrees elevated)
OGG_CHANNEL_SIDE_TOP_RIGHT = 23 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_LEFT = 24 (90 degrees left, also used for lfe left)
OGG_CHANNEL_SIDE_RIGHT = 25 (90 degrees right, also used for lfe right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 26 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_SIDE_BOTTOM = 27 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 28 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 29 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_LEFT = 30 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_RIGHT = 31 (back, 45 degrees elevated, 45 degrees right)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 32 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 33 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 34 (back, 45 degrees lowered, 45 degrees right)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 35 (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 36 (5 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 37 (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 38 (back, 5 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 39 (fed directly into the left ear canal)
OGG_CHANNEL_BINAURAL_RIGHT = 40 (fed directly into the right ear canal)
OGG_CHANNEL_SURROUND = 41 (mono, omnidirectional, diffuse)
OGG_CHANNEL_HEX_BACK_LEFT_SURROUND = 42 (back, 60 degrees left, diffuse)
OGG_CHANNEL_HEX_BACK_RIGHT_SURROUND = 43 (back, 60 degrees right, diffuse)
OGG_CHANNEL_BACK_CENTER_SURROUND = 44 (straight back, diffuse)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 45 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 46 (90 degrees right, diffuse)
OGG_CHANNEL_AMBISONICS_W = 47 (0th order, also used for lfe)
OGG_CHANNEL_AMBISONICS_X = 48 (1st order)
OGG_CHANNEL_AMBISONICS_Y = 49 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Z = 50 (1st order)
OGG_CHANNEL_AMBISONICS_R = 51 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 52 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 53 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 54 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 55 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 56 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 57 (3rd order)
OGG_CHANNEL_AMBISONICS_M = 58 (3rd order)
OGG_CHANNEL_AMBISONICS_N = 59 (3rd order)
OGG_CHANNEL_AMBISONICS_O = 60 (3rd order)
OGG_CHANNEL_AMBISONICS_P = 61 (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 62 (3rd order)
OGG_CHANNEL_UHJ_L = 63 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 64 (ambisonics UHJ right)
OGG_CHANNEL_UHJ_SIGMA = 65 (ambisonics UHJ mono/sum/mid)
OGG_CHANNEL_UHJ_DELTA = 66 (ambisonics UHJ side/difference)
OGG_CHANNEL_UHJ_T = 67 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 68 (ambisonics UHJ addition for periphony)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 69 (dolby stereo/surround left)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 70 (dolby stereo/surround right)
OGG_CHANNEL_MS_MID = 71 (cardioid response straight ahead)
OGG_CHANNEL_MS_SIDE = 49 (figure of eight response left to right, also used for ambisonics Y)
OGG_CHANNEL_XY_X = 72 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_Y = 73 (cardioid response 45 degrees to the right)
OGG_CHANNEL_LFE_LEFT = 24 (90 degrees left, also used for side left)
OGG_CHANNEL_LFE_RIGHT = 25 (90 degrees right, also used for side right)
OGG_CHANNEL_FRONT_CENTER_LEFT_LFE = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT_LFE = 4 (22.5 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_LEFT = 74 (45 degrees lowered, 22.5 degrees left, also used for front left lfe)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_RIGHT = 75 (45 degrees lowered, 22.5 degrees right, also used for front right lfe)
OGG_CHANNEL_BACK_CENTER = 76 (straight back)
OGG_CHANNEL_LFE = 47 (omnidirectional, also used for ambisonics W)
OGG_CHANNEL_BACK_STEREO_LEFT = 77 (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 78 (back, 30 degrees right)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

===== Defaulting =====

OggPCM2 streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely three channels and no explicit channel map are assumed to contain 1st order Ambisonics (W, X and Y).
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order Ambisonics (W, X, Y and Z).
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 surround in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 surround in the ITU+EX/ES back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 surround in the Dolby layout.

===== Standard Mappings =====

The OggPCM2 channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below. This list is INFORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for three-channel first order Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000002F Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000030 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000031 Channel_type OGG_CHANNEL_AMBISONICS_Y

Default mapping for four-channel first order Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000002F Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000030 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000031 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000032 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 5.1 surround in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for 6.1 surround in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x0000004C Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for 7.1 surround in the Dolby layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000018 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000005 Channel 5
32 0x00000019 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x00000006 Channel 6
32 0x0000004D Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000007 Channel 7
32 0x0000004E Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT

===== Example Conversions =====

Even if a player supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM2 format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also support rudimentary downmixing into many different layouts. However, full downmixing information may not always be available, and in any case the speaker layout rarely supports the exact requirements of all of the different channel_types. That is why some common mappings, conversions and adaptations are outlined in this section. The section is purely INFORMATIVE.

== See Also ==
*[[Ambisonics]]

== External Links ==
*[http://www.mediatwins.com/en/support/kb_topic_11.html Short info about AC-3]
*[http://www.atsc.org/standards/a_52a.pdf AC-3 spec.] Note: around p34/140 it appears to be how the channel mapping is encoded.
*[http://www.microsoft.com/whdc/device/audio/multichaud.mspx .wav extended headers (WAVE-EX) for multi channel]
*[http://en.wikipedia.org/wiki/Ambisonic Ambisonics on Wikipedia]
*[http://www.surroundassociates.com/fqmain.html General surround info]

OggPCM

2007-10-19T20:29:04Z

Decoy: added full name of the ITU 5.1 recommendation

{{draft}}
'''This page was created as an alternative to the original [[OggPCM_Draft1]]. After a [http://lists.xiph.org/pipermail/ogg-dev/2005-November/thread.html heated debate] most developers are now working on this version of the spec.'''

== Draft format 2 for OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and ambisonics signals.

==== Channel Mapping, draft 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADROPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing four channels are assumed to be B-format ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to mono files by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to stereo files basic ambisonic dematrixing W and X.

==== Channel Mapping, proposed draft 2 ====

This proposal has not yet gained the support of the Xiph community. It should be considered EXPERIMENTAL.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM2 stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used. If an error is encountered in one of the headers, the header SHOULD be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM2 stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels SHOULD be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type is encountered which is not defined for the given version of the mapping header, this SHOULD be considered an error and parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the player, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the player, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, only the first associated channel_type SHOULD be used. If a channel_type is present more than once in a Channel Mapping Header, only the first associated channel number SHOULD be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, only the first mixing coefficient for the pair SHOULD be used. Readers SHOULD still accept the header without treating it as an error, but SHOULD warn the user.

The mixing coefficients are 32 bit signed, fixed point numbers. The 16 most significant bits are the integer part (including sign), and 16 least significant parts are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined:

OGG_CHANNEL_FRONT_CENTER = 0 (ear level, straight ahead)
OGG_CHANNEL_STEREO_LEFT = 1 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 2 (30 degrees right)
OGG_CHANNEL_FRONT_CENTER_LEFT = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 4 (22.5 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 5 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 6 (45 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 7 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 8 (back, 45 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 9 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 10 (60 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 11 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 12 (back, 60 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT = 13 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 14 (back, 70 degrees right)
OGG_CHANNEL_FRONT_TOP_CENTER = 15 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 16 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_RIGHT = 17 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 18 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 19 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 20 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_SIDE_TOP_LEFT = 21 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP = 22 (90 degrees elevated)
OGG_CHANNEL_SIDE_TOP_RIGHT = 23 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_LEFT = 24 (90 degrees left, also used for lfe left)
OGG_CHANNEL_SIDE_RIGHT = 25 (90 degrees right, also used for lfe right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 26 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_SIDE_BOTTOM = 27 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 28 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 29 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_LEFT = 30 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_RIGHT = 31 (back, 45 degrees elevated, 45 degrees right)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 32 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 33 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 34 (back, 45 degrees lowered, 45 degrees right)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 35 (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 36 (5 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 37 (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 38 (back, 5 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 39 (fed directly into the left ear canal)
OGG_CHANNEL_BINAURAL_RIGHT = 40 (fed directly into the right ear canal)
OGG_CHANNEL_SURROUND = 41 (mono, omnidirectional, diffuse)
OGG_CHANNEL_HEX_BACK_LEFT_SURROUND = 42 (back, 60 degrees left, diffuse)
OGG_CHANNEL_HEX_BACK_RIGHT_SURROUND = 43 (back, 60 degrees right, diffuse)
OGG_CHANNEL_BACK_CENTER_SURROUND = 44 (straight back, diffuse)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 45 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 46 (90 degrees right, diffuse)
OGG_CHANNEL_AMBISONICS_W = 47 (0th order, also used for lfe)
OGG_CHANNEL_AMBISONICS_X = 48 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Y = 49 (1st order)
OGG_CHANNEL_AMBISONICS_Z = 50 (1st order)
OGG_CHANNEL_AMBISONICS_R = 51 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 52 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 53 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 54 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 55 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 56 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 57 (3rd order)
OGG_CHANNEL_AMBISONICS_M = 58 (3rd order)
OGG_CHANNEL_AMBISONICS_N = 59 (3rd order)
OGG_CHANNEL_AMBISONICS_O = 60 (3rd order)
OGG_CHANNEL_AMBISONICS_P = 61 (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 62 (3rd order)
OGG_CHANNEL_UHJ_L = 63 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 64 (ambisonics UHJ right)
OGG_CHANNEL_UHJ_SIGMA = 65 (ambisonics UHJ mono/sum/mid)
OGG_CHANNEL_UHJ_DELTA = 66 (ambisonics UHJ side/difference)
OGG_CHANNEL_UHJ_T = 67 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 68 (ambisonics UHJ addition for periphony)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 69 (dolby stereo/surround left)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 70 (dolby stereo/surround right)
OGG_CHANNEL_MS_MID = 71 (cardioid response straight ahead)
OGG_CHANNEL_MS_SIDE = 48 (figure of eight response left to right, also used for ambisonics X)
OGG_CHANNEL_XY_X = 72 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_Y = 73 (cardioid response 45 degrees to the right)
OGG_CHANNEL_LFE_LEFT = 24 (90 degrees left, also used for side left)
OGG_CHANNEL_LFE_RIGHT = 25 (90 degrees right, also used for side right)
OGG_CHANNEL_FRONT_CENTER_LEFT_LFE = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT_LFE = 4 (22.5 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_LEFT = 74 (45 degrees lowered, 22.5 degrees left, also used for front left lfe)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_RIGHT = 75 (45 degrees lowered, 22.5 degrees right, also used for front right lfe)
OGG_CHANNEL_BACK_CENTER = 76 (straight back)
OGG_CHANNEL_LFE = 47 (omnidirectional, also used for ambisonics W)
OGG_CHANNEL_BACK_STEREO_LEFT = 77 (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 78 (back, 30 degrees right)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

===== Defaulting =====

OggPCM2 streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order Ambisonics.
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 surround in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 surround in the ITU+EX/ES back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 surround in the Dolby layout.

===== Standard Mappings =====

The OggPCM2 channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below. This list is INFORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for first order Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000002F Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000030 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000031 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000032 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 5.1 surround in the ITU-R BS.775-1 layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for 6.1 surround in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x0000004C Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for 7.1 surround in the Dolby layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000018 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000005 Channel 5
32 0x00000019 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x00000006 Channel 6
32 0x0000004D Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000007 Channel 7
32 0x0000004E Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT

===== Example Conversions =====

Even if a player supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM2 format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also support rudimentary downmixing into many different layouts. However, full downmixing information may not always be available, and in any case the speaker layout rarely supports the exact requirements of all of the different channel_types. That is why some common mappings, conversions and adaptations are outlined in this section. The section is purely INFORMATIVE.

== Related Links ==
Short info about AC-3: http://www.mediatwins.com/en/support/kb_topic_11.html

AC-3 spec: http://www.atsc.org/standards/a_52a.pdf <br>
Note: around p34/140 it appears to be how the channel mapping is encoded.

.wav extended headers for multi channel: http://www.microsoft.com/whdc/device/audio/multichaud.mspx

General surround info: http://www.surroundassociates.com/fqmain.html

OggPCM

2007-10-19T20:28:28Z

Decoy: added full name of the ITU 5.1 recommendation

{{draft}}
'''This page was created as an alternative to the original [[OggPCM_Draft1]]. After a [http://lists.xiph.org/pipermail/ogg-dev/2005-November/thread.html heated debate] most developers are now working on this version of the spec.'''

== Draft format 2 for OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and ambisonics signals.

==== Channel Mapping, draft 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADROPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing four channels are assumed to be B-format ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to mono files by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to stereo files basic ambisonic dematrixing W and X.

==== Channel Mapping, proposed draft 2 ====

This proposal has not yet gained the support of the Xiph community. It should be considered EXPERIMENTAL.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM2 stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used. If an error is encountered in one of the headers, the header SHOULD be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM2 stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels SHOULD be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type is encountered which is not defined for the given version of the mapping header, this SHOULD be considered an error and parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the player, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the player, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, only the first associated channel_type SHOULD be used. If a channel_type is present more than once in a Channel Mapping Header, only the first associated channel number SHOULD be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, only the first mixing coefficient for the pair SHOULD be used. Readers SHOULD still accept the header without treating it as an error, but SHOULD warn the user.

The mixing coefficients are 32 bit signed, fixed point numbers. The 16 most significant bits are the integer part (including sign), and 16 least significant parts are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined:

OGG_CHANNEL_FRONT_CENTER = 0 (ear level, straight ahead)
OGG_CHANNEL_STEREO_LEFT = 1 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 2 (30 degrees right)
OGG_CHANNEL_FRONT_CENTER_LEFT = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 4 (22.5 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 5 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 6 (45 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 7 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 8 (back, 45 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 9 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 10 (60 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 11 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 12 (back, 60 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT = 13 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 14 (back, 70 degrees right)
OGG_CHANNEL_FRONT_TOP_CENTER = 15 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 16 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_RIGHT = 17 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 18 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 19 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 20 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_SIDE_TOP_LEFT = 21 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP = 22 (90 degrees elevated)
OGG_CHANNEL_SIDE_TOP_RIGHT = 23 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_LEFT = 24 (90 degrees left, also used for lfe left)
OGG_CHANNEL_SIDE_RIGHT = 25 (90 degrees right, also used for lfe right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 26 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_SIDE_BOTTOM = 27 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 28 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 29 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_LEFT = 30 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_RIGHT = 31 (back, 45 degrees elevated, 45 degrees right)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 32 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 33 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 34 (back, 45 degrees lowered, 45 degrees right)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 35 (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 36 (5 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 37 (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 38 (back, 5 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 39 (fed directly into the left ear canal)
OGG_CHANNEL_BINAURAL_RIGHT = 40 (fed directly into the right ear canal)
OGG_CHANNEL_SURROUND = 41 (mono, omnidirectional, diffuse)
OGG_CHANNEL_HEX_BACK_LEFT_SURROUND = 42 (back, 60 degrees left, diffuse)
OGG_CHANNEL_HEX_BACK_RIGHT_SURROUND = 43 (back, 60 degrees right, diffuse)
OGG_CHANNEL_BACK_CENTER_SURROUND = 44 (straight back, diffuse)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 45 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 46 (90 degrees right, diffuse)
OGG_CHANNEL_AMBISONICS_W = 47 (0th order, also used for lfe)
OGG_CHANNEL_AMBISONICS_X = 48 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Y = 49 (1st order)
OGG_CHANNEL_AMBISONICS_Z = 50 (1st order)
OGG_CHANNEL_AMBISONICS_R = 51 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 52 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 53 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 54 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 55 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 56 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 57 (3rd order)
OGG_CHANNEL_AMBISONICS_M = 58 (3rd order)
OGG_CHANNEL_AMBISONICS_N = 59 (3rd order)
OGG_CHANNEL_AMBISONICS_O = 60 (3rd order)
OGG_CHANNEL_AMBISONICS_P = 61 (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 62 (3rd order)
OGG_CHANNEL_UHJ_L = 63 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 64 (ambisonics UHJ right)
OGG_CHANNEL_UHJ_SIGMA = 65 (ambisonics UHJ mono/sum/mid)
OGG_CHANNEL_UHJ_DELTA = 66 (ambisonics UHJ side/difference)
OGG_CHANNEL_UHJ_T = 67 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 68 (ambisonics UHJ addition for periphony)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 69 (dolby stereo/surround left)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 70 (dolby stereo/surround right)
OGG_CHANNEL_MS_MID = 71 (cardioid response straight ahead)
OGG_CHANNEL_MS_SIDE = 48 (figure of eight response left to right, also used for ambisonics X)
OGG_CHANNEL_XY_X = 72 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_Y = 73 (cardioid response 45 degrees to the right)
OGG_CHANNEL_LFE_LEFT = 24 (90 degrees left, also used for side left)
OGG_CHANNEL_LFE_RIGHT = 25 (90 degrees right, also used for side right)
OGG_CHANNEL_FRONT_CENTER_LEFT_LFE = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT_LFE = 4 (22.5 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_LEFT = 74 (45 degrees lowered, 22.5 degrees left, also used for front left lfe)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_RIGHT = 75 (45 degrees lowered, 22.5 degrees right, also used for front right lfe)
OGG_CHANNEL_BACK_CENTER = 76 (straight back)
OGG_CHANNEL_LFE = 47 (omnidirectional, also used for ambisonics W)
OGG_CHANNEL_BACK_STEREO_LEFT = 77 (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 78 (back, 30 degrees right)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

===== Defaulting =====

OggPCM2 streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order Ambisonics.
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 surround in the ITU-R BS.775-1 layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 surround in the ITU+EX/ES back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 surround in the Dolby layout.

===== Standard Mappings =====

The OggPCM2 channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below. This list is INFORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for first order Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000002F Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000030 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000031 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000032 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 5.1 surround in the ITU layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for 6.1 surround in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x0000004C Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for 7.1 surround in the Dolby layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000018 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000005 Channel 5
32 0x00000019 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x00000006 Channel 6
32 0x0000004D Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000007 Channel 7
32 0x0000004E Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT

===== Example Conversions =====

Even if a player supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM2 format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also support rudimentary downmixing into many different layouts. However, full downmixing information may not always be available, and in any case the speaker layout rarely supports the exact requirements of all of the different channel_types. That is why some common mappings, conversions and adaptations are outlined in this section. The section is purely INFORMATIVE.

== Related Links ==
Short info about AC-3: http://www.mediatwins.com/en/support/kb_topic_11.html

AC-3 spec: http://www.atsc.org/standards/a_52a.pdf <br>
Note: around p34/140 it appears to be how the channel mapping is encoded.

.wav extended headers for multi channel: http://www.microsoft.com/whdc/device/audio/multichaud.mspx

General surround info: http://www.surroundassociates.com/fqmain.html

OggPCM

2007-10-19T19:19:01Z

Decoy: added the first version of draft2 channel mapping

{{draft}}
'''This page was created as an alternative to the original [[OggPCM_Draft1]]. After a [http://lists.xiph.org/pipermail/ogg-dev/2005-November/thread.html heated debate] most developers are now working on this version of the spec.'''

== Draft format 2 for OggPCM ==

The following is an draft format for OggPCM. This is a work in progress and not a final proposal. In particular, there is no agreement yet on the channel mapping extra headers.

OggPCM is an encapsulation of PCM audio data into an Ogg logical bitstream. An OggPCM bistream may be concurrently multiplexed with other Ogg logical bitstreams such as [[OggUVS]] video or [[CMML]] metadata,

Note that unless otherwise noted, all multi-byte fields use the network byte order (big endian). The first packet in a stream MUST be the main header packet. The second packet MUST be the comment packet. Some extra header packets MAY be included after the comment header, provided this is identified in the main header. The packets that follow MUST all be data packets.

=== Main Header Packet ===
Multibyte fields in the header packets are packed in big endian order, to be consistent with network byte order. A header packet contains the following fields:

64 "PCM " Codec identifier
16 0x00 Version Major (breaks backwards compatibility to increment)
16 0x00 Version Minor (backwards compatible, ie, more supported format id's)
32 [uint] PCM format
32 [uint] Sampling rate [Hz]
8 [uint] Number of significant bits
8 [uint] Number of Channels (< 256)
16 [uint] Maximum number of frames per packet
32 [uint] Number of extra header packets

A PCM "frame" is composed of samples for all channels at a given time.

The "Codec identifier" is 64 bit long since most other Ogg codecs specify their identifier within the first 64 bits rather than the first 32 bits, so this allows applications to match on all 64 bits consistently.

The "Maximum number of frames per packet" field is meant to notify an application reading the file that no data packet will contain more than a certain number of frames. This not only makes implementation easier, but also provides information on how much needs to be buffered when streaming PCM files. A value of 0 means a maximum of 65536 frames. Implementations SHOULD make this field such that packets do not get split into multiple pages.

The "Number of significant bits" field specifies how many bits are actually used. The other bits MUST be zero. This can be used to support audio with any resolution. For example, 12-bit PCM can be supported as "16 bit PCM" for the format and 12 for the number of significant bits.

For streams where the number of significant bits is the same as the bit width specified by the format, the significant bits field may be set to zero.

For streams where the number of significant bits is less than that specified by the bit width, the data shall be justified to fill the most significant bits. For 12 bit PCM in a 16 bit format, the 12 valid bits will occupy the 12 most significant bits of the 16 bit word and the least significant 4 bits shall be zero.

Since the main header packet and the comment packet are mandatory, the "extra header packets" field counts any additional header packets (aside from these two) that can be provided before the start of the data packets.

==== Supported PCM Formats ====

Format ID Short Name Description
-- Integer coding
0x00000000 OGGPCM_FMT_S8 Signed integer 8 bit
0x00000001 OGGPCM_FMT_U8 Unsigned integer 8 bit
0x00000002 OGGPCM_FMT_S16_LE Signed integer 16 bit little endian
0x00000003 OGGPCM_FMT_S16_BE Signed integer 16 bit big endian
0x00000004 OGGPCM_FMT_S24_LE Signed integer 24 bit little endian
0x00000005 OGGPCM_FMT_S24_BE Signed integer 24 bit big endian
0x00000006 OGGPCM_FMT_S32_LE Signed integer 32 bit little endian
0x00000007 OGGPCM_FMT_S32_BE Signed integer 32 bit big endian
--
-- Compressed PCM
0x00000010 OGGPCM_FMT_ULAW G.711 u-law encoding (8 bit)
0x00000011 OGGPCM_FMT_ALAW G.711 A-law encoding (8 bit)
--
-- IEEE Floating point coding
0x00000020 OGGPCM_FMT_FLT32_LE IEEE Float [-1,1] 32 bit little endian
0x00000021 OGGPCM_FMT_FLT32_BE IEEE Float [-1,1] 32 bit big endian
0x00000022 OGGPCM_FMT_FLT64_LE IEEE Float [-1,1] 64 bit little endian
0x00000023 OGGPCM_FMT_FLT64_BE IEEE Float [-1,1] 64 bit big endian

Format IDs below 0x80000000 are reserved for use by Xiph and all the ones above are allowed for application-specific formats.

=== Comment packet ===

The codec header is followed by a "vorbis comment" packet and by optional extra headers, if any. The format used is the same as for Vorbis with the exception that there is no packet identifier (so the packet is exactly like it is for Speex).

=== Data Packets ===

Data packets contain the raw PCM audio in interleaved format (complete frames are encoded sequentially) with the following definitions/restrictions:

* A PCM "frame" is composed of samples for all channels at a given time.
* Any OggPCM packet MUST only contain complete frames (ie samples for all channels at a given sampling instance). Partial frames are forbidden. It is RECOMMENDED that decoders that come across an invalid packet containing a partial frame to drop the partial frame (at the end) and issue an error.
* There is no padding allowed in a frame except when some bits (<8) are needed to complete a byte. This means that packet size has a direct relationship to the number of frames in the packet (for purposes of seeking).
* Recommended packet size is smaller than 4k since interleaving and seeking in Ogg bitstreams is done on the resolution of packets and thus larger packet sizes create suboptimal bitstreams.

=== Extra Headers (optional) ===

Extra header packets contain additional information about the OggPCM stream, and must come after the Comment Packet and before the first Data Packet. Each extra header is defined as:

32 [uint] Header ID
... Header data

The first optional headers to be defined handle mappings from physically stored channels to logical channels, such as speaker feeds and ambisonics signals.

==== Channel Mapping, draft 1 ====

===== Channel Mapping Header =====

The channel mapping header is defined as:

32 0x00000000 Header ID
16 [uint] Major version
16 [uint] Minor version
32 [uint] Channel type
32x2N [uint]Channel map (channel-target pairs)

All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions.

This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names.

Exampe values for channel types might be:

OGG_CHANNEL_MAP_MONO = 0
OGG_CHANNEL_MAP_STEREO = 1
OGG_CHANNEL_MAP_MS_WAVE = 2
OGG_CHANNEL_MAP_QUADROPHONIC = 3

and defined channels might be:

OGG_CHANNEL_FRONT_CENTER = 0
OGG_CHANNEL_FRONT_LEFT = 1
OGG_CHANNEL_FRONT_RIGHT = 2
OGG_CHANNEL_SURROUND_LEFT = 3
OGG_CHANNEL_SURROUND_RIGHT = 4
OGG_CHANNEL_SURROUND_REAR = 5
OGG_CHANNEL_REAR_LEFT = 6
OGG_CHANNEL_REAR_RIGHT = 7
OGG_CHANNEL_LFE_CENTER = 8
OGG_CHANNEL_LFE_LEFT = 9
OGG_CHANNEL_LFE_RIGHT = 10

A stereo file could thus be defined as:

channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

The channel map in this case is: "0 1 1 2".

===== Channel Mapping Defaults =====

(ideas by JMV, not yet approved by anyone else. Should be merged in respective header definition above if approved)

In order to simplify implementations when it comes to channel mappings, several defaults are defined when no extra header is present.

* Files containing one channel are assumed to be plain mono files with:
channel_type = OGG_CHANNEL_MAP_MONO
channel_map [0] = OGG_CHANNEL_FRONT_CENTER

* Files containing two channels are assumed to be stereo files with:
channel_type = OGG_CHANNEL_MAP_STEREO
channel_map [0] = OGG_CHANNEL_FRONT_LEFT
channel_map [1] = OGG_CHANNEL_FRONT_RIGHT

* Files containing four channels are assumed to be B-format ambisonic files with:
channel_type = OGG_CHANNEL_MAP_B_FORMAT
channel_map [0] = OGG_CHANNEL_W
channel_map [1] = OGG_CHANNEL_X
channel_map [2] = OGG_CHANNEL_Y
channel_map [3] = OGG_CHANNEL_Z

===== Channel Conversion Header =====

Any number of channel conversion headers can be specified. This header specifies how to down-mix the data to another format.

32 0x00000001 Remixing Header Id
16 [uint] Major version
16 [uint] Minor version
32 [uint] Target Channel type
32xMxN [sint] Target Channel (M) x Src Channel (N) Gain array

The ordering of the mixing matrix is such that source channel gains are consecutive. The gain (note: *signed* integer) has the 16 MSBs for the integer part (including sign) and 16 bits for the fracional part of the gain. Note: the gain can be negative.

===== Channel Conversion Defaults =====

* Stereo files SHOULD be converted to mono files by averaging the left channel and the right channel
* Ambisonic files SHOULD be converted to stereo files basic ambisonic dematrixing W and X.

==== Channel Mapping, proposed draft 2 ====

This proposal has not yet gained the support of the Xiph community. It should be considered EXPERIMENTAL.

Channel mappings are used to convey the meaning of the PCM signals stored in an OggPCM2 stream. They have been designed so that commonly used transmission formats like stereo, 5.1 and Ambisonics can be accurately tagged and distinguished from each other. Rudimentary downmixing from multichannel formats to stereo and mono and interoperability with compatibility formats like Dolby Surround and Ambisonics UHJ are also supported.

A channel mapping can be given in two forms, using one of two headers. The Channel Mapping header tags any subset of the transmitted channels with its intended playback semantics. The Channel Conversion Header additionally provides a mixing matrix which can be applied to the channels before interpretation as a target, logical channel type.

An arbitrary number of mapping and conversion headers can be present, including none at all. The header types can be mixed and they can appear in any order. When neither header is present, the defaults spelled out in the section below on defaulting apply. When more than one header is present, they describe alternative mappings in a decreasing preferential order, and the first supported one SHOULD be used. If an error is encountered in one of the headers, the header SHOULD be discarded and parsing SHOULD continue with the next header. If mapping headers are present but they are all erroneous, defaulting MUST NOT be applied.

The channel mapping header lists physical channels and their associated logical channels, identified by a channel_type value. It is defined as:

32 0x00000000 Channel Mapping Header ID
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x2N [uint] Channel number - channel_type pairs

The channel conversion header adds a mixing coefficient to each physical-logical routing, and explicitly allows many-to-many mappings between the two sets of channels. It is defined as:

32 0x00000001 Channel Conversion Header Id
16 0x0000 Version Major (breaks backwards compatibility to increment)
16 0x0000 Version Minor (backwards compatible, e.g. more supported format id's)
32x3N 2*[uint]+[sint] Channel number - channel_type - mixing coefficient triplets

Channel numbers refer to the physical channels transmitted in the OggPCM2 stream. They start at zero, denoting the first channel transmitted in a frame, and range to the number of channels indicated in the main header packet minus one. References to absent channels SHOULD be treated as an error. If a physical channel is not referenced in any of the channel maps and defaulting is not being used, its semantics are unknown. Such channels SHOULD NOT be played without user intervention, and SHOULD NOT be routed to audio outputs which are currently in use.

Channel_types refer to logical channels with a clear interpretation on how the sound data routed to them is to be reproduced. All channel_types less than 0x80000000 are reserved for use by Xiph; 0x80000000 and above are allowed for application specific extensions. This scheme allows for 2^31 -1 Xiph defined channel map types and 2^32 distinct channel names. If a channel_type is encountered which is not defined for the given version of the mapping header, this SHOULD be considered an error and parsing SHOULD continue with the next header. If a channel_type is encountered which is defined but is not supported by the player, parsing SHOULD also continue with the next header. If a channel_type is encountered which is both valid and supported by the player, but cannot be rendered accurately, parsing SHOULD continue with the next header. Furthermore, writers SHOULD include appropriate Channel Conversion Headers at least into stereo and mono, if possible. Finally, if no header is found which leads to an accurate rendering but at least one valid, supported header is present, approximate conversion MAY be attempted, as outlined in the section on compatibility below.

The mapping rows SHOULD be written sorted first by channel number, then by channel_type, and then by mixing coefficient. If a channel number is present more than once in a Channel Mapping Header, only the first associated channel_type SHOULD be used. If a channel_type is present more than once in a Channel Mapping Header, only the first associated channel number SHOULD be used. If a channel number - channel_type pair is present more than once in a Channel Conversion Header, only the first mixing coefficient for the pair SHOULD be used. Readers SHOULD still accept the header without treating it as an error, but SHOULD warn the user.

The mixing coefficients are 32 bit signed, fixed point numbers. The 16 most significant bits are the integer part (including sign), and 16 least significant parts are the fraction. Note that the gain can be negative.

For major version 0, minor version 0 of the Channel Mapping and Channel Conversion headers, the following channel_type values are defined:

OGG_CHANNEL_FRONT_CENTER = 0 (ear level, straight ahead)
OGG_CHANNEL_STEREO_LEFT = 1 (30 degrees left)
OGG_CHANNEL_STEREO_RIGHT = 2 (30 degrees right)
OGG_CHANNEL_FRONT_CENTER_LEFT = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT = 4 (22.5 degrees right)
OGG_CHANNEL_QUAD_FRONT_LEFT = 5 (45 degrees left)
OGG_CHANNEL_QUAD_FRONT_RIGHT = 6 (45 degrees right)
OGG_CHANNEL_QUAD_BACK_LEFT = 7 (back, 45 degrees left)
OGG_CHANNEL_QUAD_BACK_RIGHT = 8 (back, 45 degrees right)
OGG_CHANNEL_HEX_FRONT_LEFT = 9 (60 degrees left)
OGG_CHANNEL_HEX_FRONT_RIGHT = 10 (60 degrees right)
OGG_CHANNEL_HEX_BACK_LEFT = 11 (back, 60 degrees left)
OGG_CHANNEL_HEX_BACK_RIGHT = 12 (back, 60 degrees right)
OGG_CHANNEL_ITU_BACK_LEFT = 13 (back, 70 degrees left)
OGG_CHANNEL_ITU_BACK_RIGHT = 14 (back, 70 degrees right)
OGG_CHANNEL_FRONT_TOP_CENTER = 15 (45 degrees elevated)
OGG_CHANNEL_FRONT_TOP_LEFT = 16 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_TOP_RIGHT = 17 (45 degrees elevated, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_CENTER = 18 (45 degrees lowered)
OGG_CHANNEL_FRONT_BOTTOM_LEFT = 19 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_FRONT_BOTTOM_RIGHT = 20 (45 degrees lowered, 45 degrees left)
OGG_CHANNEL_SIDE_TOP_LEFT = 21 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_TOP = 22 (90 degrees elevated)
OGG_CHANNEL_SIDE_TOP_RIGHT = 23 (45 degrees elevated, 90 degrees left)
OGG_CHANNEL_SIDE_LEFT = 24 (90 degrees left, also used for lfe left)
OGG_CHANNEL_SIDE_RIGHT = 25 (90 degrees right, also used for lfe right)
OGG_CHANNEL_SIDE_BOTTOM_LEFT = 26 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_SIDE_BOTTOM = 27 (90 degrees lowered)
OGG_CHANNEL_SIDE_BOTTOM_RIGHT = 28 (45 degrees lowered, 90 degrees left)
OGG_CHANNEL_BACK_TOP_CENTER = 29 (back, 45 degrees elevated)
OGG_CHANNEL_BACK_TOP_LEFT = 30 (back, 45 degrees elevated, 45 degrees left)
OGG_CHANNEL_BACK_TOP_RIGHT = 31 (back, 45 degrees elevated, 45 degrees right)
OGG_CHANNEL_BACK_BOTTOM_CENTER = 32 (back, 45 degrees lowered)
OGG_CHANNEL_BACK_BOTTOM_LEFT = 33 (back, 45 degrees lowered, 45 degrees left)
OGG_CHANNEL_BACK_BOTTOM_RIGHT = 34 (back, 45 degrees lowered, 45 degrees right)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_LEFT = 35 (5 degrees left)
OGG_CHANNEL_FRONT_STEREO_DIPOLE_RIGHT = 36 (5 degrees right)
OGG_CHANNEL_BACK_STEREO_DIPOLE_LEFT = 37 (back, 5 degrees left)
OGG_CHANNEL_BACK_STEREO_DIPOLE_RIGHT = 38 (back, 5 degrees right)
OGG_CHANNEL_BINAURAL_LEFT = 39 (fed directly into the left ear canal)
OGG_CHANNEL_BINAURAL_RIGHT = 40 (fed directly into the right ear canal)
OGG_CHANNEL_SURROUND = 41 (mono, omnidirectional, diffuse)
OGG_CHANNEL_HEX_BACK_LEFT_SURROUND = 42 (back, 60 degrees left, diffuse)
OGG_CHANNEL_HEX_BACK_RIGHT_SURROUND = 43 (back, 60 degrees right, diffuse)
OGG_CHANNEL_BACK_CENTER_SURROUND = 44 (straight back, diffuse)
OGG_CHANNEL_SIDE_LEFT_SURROUND = 45 (90 degrees left, diffuse)
OGG_CHANNEL_SIDE_RIGHT_SURROUND = 46 (90 degrees right, diffuse)
OGG_CHANNEL_AMBISONICS_W = 47 (0th order, also used for lfe)
OGG_CHANNEL_AMBISONICS_X = 48 (1st order, also used for mid/side side)
OGG_CHANNEL_AMBISONICS_Y = 49 (1st order)
OGG_CHANNEL_AMBISONICS_Z = 50 (1st order)
OGG_CHANNEL_AMBISONICS_R = 51 (2nd order)
OGG_CHANNEL_AMBISONICS_S = 52 (2nd order)
OGG_CHANNEL_AMBISONICS_T = 53 (2nd order)
OGG_CHANNEL_AMBISONICS_U = 54 (2nd order)
OGG_CHANNEL_AMBISONICS_V = 55 (2nd order)
OGG_CHANNEL_AMBISONICS_K = 56 (3rd order)
OGG_CHANNEL_AMBISONICS_L = 57 (3rd order)
OGG_CHANNEL_AMBISONICS_M = 58 (3rd order)
OGG_CHANNEL_AMBISONICS_N = 59 (3rd order)
OGG_CHANNEL_AMBISONICS_O = 60 (3rd order)
OGG_CHANNEL_AMBISONICS_P = 61 (3rd order)
OGG_CHANNEL_AMBISONICS_Q = 62 (3rd order)
OGG_CHANNEL_UHJ_L = 63 (ambisonics UHJ left)
OGG_CHANNEL_UHJ_R = 64 (ambisonics UHJ right)
OGG_CHANNEL_UHJ_SIGMA = 65 (ambisonics UHJ mono/sum/mid)
OGG_CHANNEL_UHJ_DELTA = 66 (ambisonics UHJ side/difference)
OGG_CHANNEL_UHJ_T = 67 (ambisonics UHJ addition for pantophony)
OGG_CHANNEL_UHJ_Q = 68 (ambisonics UHJ addition for periphony)
OGG_CHANNEL_DOLBY_STEREO_LEFT = 69 (dolby stereo/surround left)
OGG_CHANNEL_DOLBY_STEREO_RIGHT = 70 (dolby stereo/surround right)
OGG_CHANNEL_MS_MID = 71 (cardioid response straight ahead)
OGG_CHANNEL_MS_SIDE = 48 (figure of eight response left to right, also used for ambisonics X)
OGG_CHANNEL_XY_X = 72 (cardioid response 45 degrees to the left)
OGG_CHANNEL_XY_Y = 73 (cardioid response 45 degrees to the right)
OGG_CHANNEL_LFE_LEFT = 24 (90 degrees left, also used for side left)
OGG_CHANNEL_LFE_RIGHT = 25 (90 degrees right, also used for side right)
OGG_CHANNEL_FRONT_CENTER_LEFT_LFE = 3 (22.5 degrees left)
OGG_CHANNEL_FRONT_CENTER_RIGHT_LFE = 4 (22.5 degrees right)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_LEFT = 74 (45 degrees lowered, 22.5 degrees left, also used for front left lfe)
OGG_CHANNEL_FRONT_BOTTOM_CENTER_RIGHT = 75 (45 degrees lowered, 22.5 degrees right, also used for front right lfe)
OGG_CHANNEL_BACK_CENTER = 76 (straight back)
OGG_CHANNEL_LFE = 47 (omnidirectional, also used for ambisonics W)
OGG_CHANNEL_BACK_STEREO_LEFT = 77 (back, 30 degrees left)
OGG_CHANNEL_BACK_STEREO_RIGHT = 78 (back, 30 degrees right)

Unless otherwise indicated, the logical channels are assumed to be speaker feeds, with the speaker lying in the indicated direction. The direction is referenced to either the front center, or where indicated, the back center speaker. By default all of the speakers SHOULD be at the same distance from the listener, or the so called "sweet spot", so that temporally coincident signals give rise to temporally coincident sound at the listening position. Where the channel_type indicates an interpretation other than a speaker feed, temporal coincidence SHOULD still hold.

Some of the base standards used to derive the channel mappings are sensitive to speaker distance in addition to any possible time delay, and some are not. In any case interoperability between the different standards calls for setting the distance. The base standards used to derive the channel map rarely take a stance on that, so for the purposes of this specification the speaker distance, the listening area, and the Ambisonics coding radius are all idealized as being infinite. Hence, the field produced by any speaker near the sweet spot SHOULD approximate a planar wave, and if this cannot be achieved, an effort SHOULD be made to compensate for the difference e.g. electronically.

===== Defaulting =====

OggPCM2 streams were originally defined without channel maps, so for compatibility purposes, the simplest cases are defaulted based on the number of physical channels present. The precise Channel Mapping Headers and Channel Conversion headers that are implied can be found below, in the list of standard mappings.

* Files containing precisely one channel and no explicit channel map are assumed to contain plain mono.
* Files containing precisely two channels and no explicit channel map are assumed to contain plain stereo.
* Files containing precisely four channels and no explicit channel map are assumed to contain 1st order Ambisonics.
* Files containing precisely six channels and no explicit channel map are assumed to contain 5.1 surround in the ITU layout.
* Files containing precisely seven channels and no explicit channel map are assumed to contain 6.1 surround in the ITU+EX/ES back channel layout.
* Files containing precisely eight channels and no explicit channel map are assumed to contain 7.1 surround in the Dolby layout.

===== Standard Mappings =====

The OggPCM2 channel mapping approach is based on supersetting existing standards, and logical extension where appropriate. Hence a large number of shared channel_types exists, which can make it difficult to find the right set even when encoding to an existing standard. To ease this task, default mappings for several existing standards are set out below. This list is INFORMATIVE.

Default mapping for plain mono:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER

Default mapping for plain stereo:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT

Default mapping for first order Ambisonics:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x0000002F Channel_type OGG_CHANNEL_AMBISONICS_W
32 0x00000001 Channel 1
32 0x00000030 Channel_type OGG_CHANNEL_AMBISONICS_X
32 0x00000002 Channel 2
32 0x00000031 Channel_type OGG_CHANNEL_AMBISONICS_Y
32 0x00000003 Channel 3
32 0x00000032 Channel_type OGG_CHANNEL_AMBISONICS_Z

Default mapping for 5.1 surround in the ITU layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT

Default mapping for 6.1 surround in the ITU+EX/ES back channel layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x0000000D Channel_type OGG_CHANNEL_ITU_BACK_LEFT
32 0x00000005 Channel 5
32 0x0000000E Channel_type OGG_CHANNEL_ITU_BACK_RIGHT
32 0x00000006 Channel 6
32 0x0000004C Channel_type OGG_CHANNEL_BACK_CENTER

Default mapping for 7.1 surround in the Dolby layout:
32 0x00000000 Channel Mapping Header
16 0x0000 Version Major 0
16 0x0000 Version Minor 0
32 0x00000000 Channel 0
32 0x00000001 Channel_type OGG_CHANNEL_STEREO_LEFT
32 0x00000001 Channel 1
32 0x00000002 Channel_type OGG_CHANNEL_STEREO_RIGHT
32 0x00000002 Channel 2
32 0x00000000 Channel_type OGG_CHANNEL_FRONT_CENTER
32 0x00000003 Channel 3
32 0x0000002F Channel_type OGG_CHANNEL_LFE
32 0x00000004 Channel 4
32 0x00000018 Channel_type OGG_CHANNEL_SIDE_LEFT
32 0x00000005 Channel 5
32 0x00000019 Channel_type OGG_CHANNEL_SIDE_RIGHT
32 0x00000006 Channel 6
32 0x0000004D Channel_type OGG_CHANNEL_BACK_STEREO_LEFT
32 0x00000007 Channel 7
32 0x0000004E Channel_type OGG_CHANNEL_BACK_STEREO_RIGHT

===== Example Conversions =====

Even if a player supports a given channel_type, it is not always possible to recreate the precise intention of the coder because of differences and uncertainties in the available speaker layout. The first fallback offered by the OggPCM2 format is the preferential hierarchy of Channel Mapping and Channel Conversion Headers, which allow the coder to both include multiple separate mixes for different layouts, and also support rudimentary downmixing into many different layouts. However, full downmixing information may not always be available, and in any case the speaker layout rarely supports the exact requirements of all of the different channel_types. That is why some common mappings, conversions and adaptations are outlined in this section. The section is purely INFORMATIVE.

== Related Links ==
Short info about AC-3: http://www.mediatwins.com/en/support/kb_topic_11.html

AC-3 spec: http://www.atsc.org/standards/a_52a.pdf <br>
Note: around p34/140 it appears to be how the channel mapping is encoded.

.wav extended headers for multi channel: http://www.microsoft.com/whdc/device/audio/multichaud.mspx

General surround info: http://www.surroundassociates.com/fqmain.html

OggPCM

2007-10-19T14:27:23Z

Decoy: made channel mappings a section, intend to add a refined, competing version