Re: [AVTCORE] SSRC multiplexing of RTP

The rtp-cnames document seems to give good advice.

Statements that make me want to stay away from SSRC multiplexing is for 
example what is stated in RFC 3550 RTP
in 6.2.1
  "New sites are added to the count when they are heard, and an entry 
for each SHOULD be created in a table indexed by the SSRC or CSRC 
identifier (see Section 8.2) to keep track of them. New entries MAY be 
considered not valid until multiple packets carrying the new SSRC have 
been received "

If a source is regarded not valid, I see a risk that RTP implementations 
ignore packets from that source.

/Gunnar

Ali C. Begen (abegen) skrev 2011-03-14 18:30:
>
>> -----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
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