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Re: [AVTCORE] SSRC multiplexing of RTP

"Ali C. Begen (abegen)" <abegen@cisco.com> Mon, 14 March 2011 17:29 UTC

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Date: Mon, 14 Mar 2011 10:30:15 -0700
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Thread-Topic: [AVTCORE] SSRC multiplexing of RTP
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References: <11120238-4159-4BA7-B150-0B28E86651B3@cisco.com><4D7798A9.7080006@omnitor.se> <4D779F79.8090001@ericsson.com><4D79FEC3.9060204@alvestrand.no> <4D7E3F9C.4010505@ericsson.com> <19838.19728.906691.771074@amman.clic.cs.columbia.edu>
From: "Ali C. Begen (abegen)" <abegen@cisco.com>
To: lennox@cs.columbia.edu, Magnus Westerlund <magnus.westerlund@ericsson.com>
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Cc: Harald Alvestrand <harald@alvestrand.no>, avt@ietf.org
Subject: Re: [AVTCORE] SSRC multiplexing of RTP
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> -----Original Message-----
> From: avt-bounces@ietf.org [mailto:avt-bounces@ietf.org] On Behalf Of lennox@cs.columbia.edu
> Sent: Monday, March 14, 2011 1:15 PM
> To: Magnus Westerlund
> Cc: Harald Alvestrand; avt@ietf.org
> Subject: Re: [AVTCORE] SSRC multiplexing of RTP
> 
> On Monday, March 14 2011, "Magnus Westerlund" wrote to "Harald Alvestrand, avt@ietf.org" saying:
> 
> > > - if it is a new stream, how to tell that it's a new stream
> > > - if it is an old stream, renumbered, how to tell what the old stream was
> >
> > I don't think the specs are that unclear on what is what. You do need
> > the CNAME to determine which case it is. Sure it can be clarified. I
> > mostly think the issue is with the state of the implementations. They
> > haven't considered the implications and need for multiple SSRC support.
> 
> There are valid cases where multiple independent streams will have the same
> CNAME -- if they're multiple sources from the same participant.  Multiple
> video streams in the Telepresence/CLUE environment are probably the current
> most prominent example of this, but generally, this will be the case if you
> have multiple streams that all need to be synchronized together.

CNAME would be used to relate a source stream with its FEC stream as well. The cname guidelines document is a useful read:
http://tools.ietf.org/html/draft-ietf-avt-rtp-cnames-05

-acbegen
 
> --
> Jonathan Lennox
> lennox@cs.columbia.edu
> _______________________________________________
> Audio/Video Transport Core Maintenance
> avt@ietf.org
> https://www.ietf.org/mailman/listinfo/avt

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