Re: [MMUSIC] Draft on source-specific SDP attributes: draft-lennox-mmusic-sdp-source-attributes-00

On 19 Mar 2007, at 10:38, Jonathan Lennox wrote:
> Colin Perkins wrote:
>> Can you comment on the interactions between parameters specified in
>> "a=fmtp:" lines and those specified in "a=ssrc: fmtp" lines? There
>> would seem to be the potential for significant confusion here, yet
>> the draft goes into relatively little detail.
>
> Source-specific fmtp parameters are going to need to be defined per- 
> format;
> I don't think there's much you can meaningfully say about them on a
> format-independent basis.
>
> The particular use case I'm thinking about here is when you have  
> several
> H.264 streams with different (and incompatible) parameter sets in  
> an RTP
> session, and you want to send parameter sets out of band (as  
> recommended by
> RFC 3984).  There's no way to support this with SDP at present.

Sure, but there are potential problems if conflicting format  
parameters are specified at media and source level.

>> Also, what are the interactions between congestion control and the
>> media source bandwidth attribute? The are already problems with
>> reconciling this with media level "b=" attributes: will these get
>> worse with media source bandwidth attributes?
>
> It doesn't solve the problem, but I don't think it makes it worse.  
> Basically
> this just allocates the (sending) media bandwidth among the sources.

We do need to be clear that these are not a substitute for congestion  
control, though.

-- 
Colin Perkins
http://csperkins.org/

_______________________________________________
mmusic mailing list
mmusic@ietf.org
https://www1.ietf.org/mailman/listinfo/mmusic