[xiph-rtp] Re: [Speex-dev] new RTP development list

[Aaron Colwell]

On Wed, Oct 20, 2004 at 08:30:03PM +0200, Tor-Einar Jarnbjo wrote:
> Onsdag, 20 oktober 2004, skrev Aaron Colwell <acolwell at real.com>:
> 
> >Why are chained streams not going to be supported? I looked at the wiki
> >pages and I don't agree with the arguments for dropping chaining 
> support.
> 
> Well, one major obstacle is that common control protocols for RTP 
> sessions (RTSP and SDP) are not directly supporting all the chaining 
> mechanisms. E.g., you cannot simply change the sample rate or number 
> of channels within a session as these are specified in the session's 
> SDP descriptor.

Why not just pick a master sample rate with sufficient resolution to
acommodate all the chains. If you still want to maintain sample accurate
timestamps then you can put a field in the payload that contains the part
that got rounded off when converting to the master sample rate. This allows
the RTP timestamp sample rate to stay constant while the actual sample rate
of the stream contents can vary. This mechanism can also apply to Theora
streams where the frame rate changes.

> 
> A simple workaround would be to use RTSP for the same functionality 
> as chaining is used now. If I'm not completely wrong, it would be 
> a straight forward task for an RTP server to inform the client using 
> RTSP that the session is about to end and recommend the client to 
> switch over to another specified session, which is then setup using 
> completely different parameters if necessary.

I think creating this sort of binding between RTSP and RTP is a large burden
and defeats the purpose of having the 2 protocols decoupled to begin with.
With the solution proposed above, you wouldn't need this anyways.

Aaron

> 
> Tor
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>