OggOpus: Difference between revisions
(→Ogg mapping for Opus: Sketch what I understand so far about requirements) |
(→Draft spec: Lowercase the non-initial bytes of the magic) |
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Id header: | Id header: | ||
- 8 byte magic signature ' | - 8 byte magic signature 'Opus\0\0\0\0' | ||
- <custom mode flags> | - <custom mode flags> | ||
| Line 24: | Line 24: | ||
- follows the vorbis-comment header design used in OggVorbis, OggTheora, and Speex. | - follows the vorbis-comment header design used in OggVorbis, OggTheora, and Speex. | ||
- Magic is ' | - Magic is 'Opus\0\0\001' | ||
Revision as of 14:00, 22 July 2011
Ogg mapping for Opus
The IETF Opus codec is a low-latency audio codec optimized for both voice and general-purpose audio. See [tools.ietf.org/html/draft-ietf-codec-opus the spec] for technical details.
Almost everything about this codec is either fixed or dynamically switchable, so the usual id and setup header parameters in a the header packets of an Ogg encapsulation aren't useful. In particular, bitrate, frame size, mono/stereo, and coding modes are all dynamically switchable from packet to packet. A one-byte header on each data packet defines the parameters for that particular packet.
Remaining parameters we need to signal are:
- magic number for stream identification
- comment/metadata tags
Additionally there's been a desire to support some kind of channel bonding for surround, and some kind of option signalling for "Opus Custom", in particular the granulerate.
Draft spec
Two headers: id, comment
Id header:
- 8 byte magic signature 'Opus\0\0\0\0' - <custom mode flags>
Comment header:
- follows the vorbis-comment header design used in OggVorbis, OggTheora, and Speex. - Magic is 'Opus\0\0\001'