Re: [AVTCORE] SSRC multiplexing of RTP

I have a doubt with SSRC multiplexing. When two multiplexed SSRC sessions
appear in a RTP session, do have two separate sequence number series or
share the same. Also in unicast sessions when the receiver receives two such
sessions what does it considers the two streams as?

-PC

2011/3/15 Gunnar Hellström <gunnar.hellstrom@omnitor.se>

> 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
>>> avt@ietf.org
>>> https://www.ietf.org/mailman/listinfo/avt
>>>
>> _______________________________________________
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