[theora-dev] Multiplexed Ogg and header problems.

Monty xiphmont at xiph.org
Wed Nov 27 23:29:25 PST 2002

On Fri, Nov 08, 2002 at 04:13:06PM -0300, Alejandro G. Belluscio wrote:
>   I there was a discussion on the vorbis list about Real Audio
>   SureStream (tm) format. The basic idea was that they put multiple RA
>   files with different compression levels. So when they have to switch
>   the bit rate due to bandwidth changes, they choose from the streams
>   they have. Since peeling is a long time away, 

It's not that it's a long way away, more that it's tricky and my
personal implementation model requires encoder support to make it work
really well.  I'm not sure that it's substantially harder than
implementing the multiple-stream model, it just requires more

>   it could be implemented
>   with ogg vorbis multiplexing several times the same file with
>   different compression levels. My question (and I think Monty can
>   answer it) is how should the the presence of multiple concurrent
>   vorbis streams be handled. Because if you have multiple audio tracks
>   for a movie, or you have multiple compression rates it's very similar.
>   The only problem seems to identify what's each of those streams for.
>   In other word, how should I know that stream A is Swahili and stream B
>   is Speranto, or that stream A is the -q3 compressed and Stream B is
>   the -q1 compressed?

Well... how specilised an implementation do you want?  The most
flexible solution (in the multi-stream vein) would be to have a
multiplexed file on the server side, and a server that is smart enough
to hide whatever stream was actually in use into a single output
stream and single header that switched back and forth without the
client ever knowing...  Or one could switch streams witht he client
fully aware of different headers, it just decodes whatever it's
getting at the moment....

More than one way to tackle this beast.  The Perl-like mixed-curse.

(Personally, I'd rather code peeling.  Certainly there's been much
more clamor for this feature recently.  It's time to start bumping it
up on my priority list.)

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