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

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.

> 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.

It probably interacts with the send-bandwidth attribute, though.

-- 
Jonathan Lennox -- Layered Media
jonathan@layeredmedia.com

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