[vorbis-dev] audio/vorbis media type registration

[rillian]

On Saturday, May 19, 2001, at 10:33 , Monty wrote:

> The master TOC on multiplexed Ogg files (which don't yet exist; Vorbis
> is using the degenerate case), will tag streams by media type such
> that it is possible to identify audio, video, whatever, without having
> codec knowledge.

I'm fine with adding this to the toc-format requirements list, though I 
think it's of limited usefulness. To do much of the "manipulation and 
playback" the original post mentions you have to be able to match the 
substreams with their specific codec implementations. I only see this 
has helpful for "copy out all the audio tracks" or something like that. 
But it's easy to add.

Monty, could you please articulate your idea for this master TOC more 
clearly? I spoke to Jack about it last week, and he seemed to thinking 
of some kind of special glued-on-the-front section. I really *don't* 
think that's the way to go. There's no way to do magic detection this 
way, at it either breaks the simplicity of the current spec, or carries 
information over a chaining boundary.

I think we're much better off with the primary-substream first method:

     audio/vorbis is any ogg file with a vorbis header packet in the 
first page. Any other bitstreams may follow (and be ignored at the 
player's discretion).

     video/tarkin is any ogg file with a tarkin header packet (which, 
like vorbis begins with the magic 'tarkin' string) in the first page, 
optionally followed by other bitstream headers.

     application/ogg is anything else that starts with 'OggS'.

That nicely grandfathers in degenerate streams, and means the TOC (which 
would be in its own logical bitstream) can continue to be optional 
except when there are 'dvd' features that require it: alternate audio or 
video tracks, overlays and subtitiles. In practice, I'd put it after the 
primary audio stream or after the primary video and audio streams in a 
video file.
Once we fix the ignoring-other-substreams bug, we can be free to use 
degenerate streams forever without player compatibility problems.

IMNSO,
  -ralph

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-dev-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.