Subject: Re: [AVTCORE] Fwd: I-D Action: draft-westerlund-avtcore-rtp-topologies-update-01.txt

From: Magnus Westerlund <[email-masked]>
Date: Wed, 14 Nov 2012 15:57:05 +0100

Hi,

Sorry for the delay in responding.

On 2012-10-25 15:00, Roni Even wrote:
> Hi Magnus,
> I read the draft so to answer the questions
> 
> 1. I think the document need also to discuss the SDES behavior (CNAME must
> be forwarded to support the CSRC) specified in 7.2 and 7.3 of RFC 3550 for
> the different topologies (we had recently a discussion about using SDES
> messages). 

Yes, that is a good idea.

> 2. I did not fully understand the SSRC behavior for source projecting
> middlebox and how it is different from the topologies in 3.5.

The difference between a RTP mixer and a source projecting mixer and its
usage of SSRCs are as follow.

Source projection: SSRC has a one to one relation to a CSRC
RTP Mixer: Has one SSRC that carries content from potentially multiple
CSRCs.

The big difference is that an RTP mixer's SSRC contains either a
selection or a media level mix/composition of the contributed media
streams. A source projection mixer really is a way of projecting the
other media sources in the conference into the RTP session between the
Mixer and this particular conference participant.

Does this make it clearer?

Cheers

Magnus Westerlund

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