[vorbis] Split Ogg Files

[Kenneth Arnold]

On Tue, Aug 07, 2001 at 12:06:50PM -0600, David Mitchell wrote:
> Michael Smith wrote:
> 
> > 
> > Actually, that's exactly the right way to do it. Some players might treat
> > it a bit strangely (time display, seeking, etc. might be a bit 'weird' in
> > some players, though most of them are fine), but they should all play it
> > correctly.
> 
> This is something I've just been wondering about. I'm playing
> around with using the
> ogg_* and vorbis_* functions directly instead of ov_*, and I'm
> not sure how to
> handle multiple streams. Right now, it's probably safe to ignore
> streams entirely,
> and just get pages out of ogg_sync and push them all up to the
> vorbis decoder. But,
> in the future, there might be multiple concurrent audio streams
> in a file, right? 
> Even now, we might see chained streams in a single file.

AFAIK all icecast2 Vorbis streams at the moment are chained streams
(or at least a chained stream is a common way to assemble streaming
media).

To answer just about all of your questions, I'd highly suggest reading
through vorbisfile.c in the libvorbis sources, which implement the
ov_* functions you had been using. Note, however, that vorbisfile only
understands the degenerate file format we have now -- foresight for
Ogg includes a standardized TOC-style header as well as some form of
unified metadata (any progress at all on these?). So yes, in the
future there may be files with multiple simultaneous audio streams
interleaved into the same bitstream, and the task of pulling packets
out of the Ogg layer and shuttling them to the codecs will get
significantly more involved, even just finding which codecs will
decode which packets and loading them if they're not available
(assuming that Vorbis will indeed be, as its creators suggest, the
first in a line of several codecs, both audio and video, or any other
unforseen applications of the Ogg media format). 


-- 
Kenneth Arnold <ken at arnoldnet.net> / kcarnold / Linux user #180115
http://arnoldnet.net/~kcarnold/



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