Re: [AVT] Vorbis RTP issues list for Vienna

[John Lazzaro <lazzaro@CS.Berkeley.EDU>]

> Aaron Colwell <acolwell@real.com> writes:
> I agree with Ross on this. It seems that these codebooks are causing too
> many problems that aren't worth dealing with. People have been suggesting
> getting the codebooks via HTTP, alternate TCP links, and all sorts of
> other methods. If your going to go that far why not just use HTTP to
> deliver the data. That way you are guaranteed to get everything in the
> right order.

I think its just an instance of a general problem -- transport of
hybrid streams with two components:

  -- A steady flow of media information that can handle the 
     occassional packet loss episode gracefully and without
     retransmission

  -- Occassional chunks of data, which can be sent well ahead of
     its need, which needs reliability, and which is synchronous
     to the media flow.

So, I think its a good idea for RTP to offer solutions that work
in this domain.  There are some studio-oriented uses of RTP MIDI
which fit into the model, and my motivation for doing 
draft-lazzaro-avt-rtp-framing-contrans-01 is to support those in
a general way, so that when things like Vorbis codebooks come
along, RTP has a way to support them.  I really don't think that
posing the question as all-or-none -- RTP streaming or Shoutcast-esqe
pseudo-streaming -- benefits AVT, it will just spawn more HTTP
streaming implementations.

That said:

> The Vorbis folks
> should come up with a "streamable" profile that encodes the audio using
> predefined codebooks.

This is a good option too -- my guess is that most Vorbis setups
will only need one codebook for the life of the stream, and that
need will be known in advance.  A URL in the session description
to support HTTP download of that one codebook would be a way to
go, with perhaps a known set of "standard codebooks" codable by
speak tokens or by GUIDs for the MIME HTTP codebook object.

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John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu     www.cs.berkeley.edu/~lazzaro
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