[vorbis-dev] RFC draft for Vorbis over RTP

[Tor-Einar Jarnbjo]

Onsdag, 26 mai 2004, skrev du:

>All the files produced by current encoders
>use the same set of codebooks for the same configurations anyways. 

Yes, but this is only valid for the current encoders. A future encoder 
may choose to create the codebooks while encoding, making an optimized 
set for the current input. Like sort of integrating Segher's tool 
(which name I've forgotten) with a current encoder. A chain with 
two such files would then not be streamable.

>I'm not saying "pick a set of codebooks" for everything.  I'm saying
>send a single set of codebooks on setup, and restrict the stream to
>_that_ set for the duration.  Essentially disallowing chains over RTP.

Yes, but I'm not sure if I like that limitation. Broadcasters are 
currently using chains to allow a midstream change in the metadata 
(comment header, title, artist) and this is a feature which should 
be preserved when using RTP too. One option would of course be to 
allow comment headers to appear between audio packets.  

>We don't change codebooks "on the fly".  New encoders use new codebooks.

>All current encoders that I know of have used a fixed set of codebooks
>for that encoder generation.  But there are several generations 
of these
>fixed sets.

Yes, this is the current state, but as I wrote earlier, it could 
be reasonable for future encoders to either have more fixed codebook 
settings for the same quality setting, selecting different codebook 
sets, depending on the encoded audio, or even generate new codebooks 
while encoding.

>Exactly.  I think in the case of streaming, it is more or less expected
>that a stream will have a fixed set of parameters.  I can't think 
of any
>counter arguments off the top of my head, so this idea seems like a
>valid and worthy compromise.

So what do you think about restricting the identification header 
and the setup header to remain static for the entire broadcast, but 
allow the comment header to be repeated? Or perhaps use some other 
content type to deliver meta data?

Tor

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