Ogg

From XiphWiki

Jump to: navigation, search

The Ogg transport bitstream is designed to provide framing, error protection and seeking structure for higher-level codec streams that consist of raw, unencapsulated data packets, such as the Vorbis audio codec or Theora video codec.

Contents

[edit]

Name

Ogg derives from "ogging", jargon from the computer game Netrek. Ogg is not an acronym and should not be mentioned as "OGG".

[edit]

Design constraints for Ogg bitstreams

  • True streaming; we must not need to seek to build a 100% complete bitstream.
  • Use no more than approximately 1-2% of bitstream bandwidth for packet boundary marking, high-level framing, sync and seeking.
  • Specification of absolute position within the original sample stream.
  • Simple mechanism to ease limited editing, such as a simplified concatenation mechanism.
  • Detection of corruption, recapture after error and direct, random access to data at arbitrary positions in the bitstream.
[edit]

Projects using Ogg

[edit]

Codecs

[edit]

Servers

[edit]

Developer info

  • GranulePosAndSeeking -- a discussion of the interpretation of granulepos, and the algorithm for seeking on Ogg files
[edit]

Ogg page format

The LSb (least significant bit) comes first in the Bytes. Fields with more than one byte length are encoded LSB (least significant byte) first. 

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1| Byte
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | capture_pattern: Magic number for page start "OggS"           | 0-3
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | version       | header_type   | granule_position              | 4-7
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               | 8-11
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                               | bitstream_serial_number       | 12-15
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                               | page_sequence_number          | 16-19
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                               | CRC_checksum                  | 20-23
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                               |page_segments  | segment_table | 24-27
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | ...                                                           | 28-
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


[edit]

Implementations

The Ogg encapsulation format can be handled with the following libraries:

  • libogg: libogg svn (C, cross-platform) Low-level Ogg parsing and writing.
  • liboggz: liboggz svn or liboggz (C, cross-platform) liboggz wraps libogg and provides features such as seeking.
  • the Ogg Directshow filters: see illiminable (C++, Win32)
  • HOgg (pure Haskell)
  • JOrbis (pure Java) contains com.jcraft.jogg
  • Mutagen (pure Python)
[edit]

See also

[edit]

External links

Retrieved from "http://wiki.xiph.org/index.php/Ogg"
Personal tools