Re: [AVTCORE] draft-westerlund-avtcore-multiplex-architecture-01 - same SSRC for SVC

["Roni Even" <[e-mail]>]

Hi,
I will just address the SVC multiplexing issue and start a different thread
on the session and ssrc multiplexing and the relation between RTP session
and the transport infrastructure used which is also discussed in
draft-alvestrand-rtp-sess-neutral-00.

As for the SVC example in the document, I think that the reason for MST mode
is because the idea is to use the session multiplexing based on different
UDP ports to divide the streams, for example in multicast allowing the users
to join just the relevant multicast groups. IF you want SSRC multiplexing in
SVC you can use SST (Single Session Transmission) mode and I think this is
the reason there is no need to address SSRC multiplexing using multiple
sessions to a single UDP receive port is not discussed.

What I am saying is that the example in 3.2 is not correct since it was not
addressed on purpose being non relevant use for MST.
Roni Even

> -----Original Message-----
> From: Magnus Westerlund [mailto:[e-mail]]
> Sent: Friday, March 16, 2012 5:07 PM
> To: Roni Even
> Cc: 'IETF AVTCore WG'
> Subject: Re: [AVTCORE] draft-westerlund-avtcore-multiplex-architecture-
> 01 - same SSRC
> 
> On 2012-03-16 14:41, Roni Even wrote:
> > Hi Magnus,
> > I thought that RFC5583 is used to signal the media decoding
> dependency
> > between the different sessions as mentioned in section 7.2.3 of RFC
> 6190.
> > I also think that this allows you to provide also the SSRC value of
> > the different RTP streams.
> 
> No, to my understanding RFC 5583 only defines how the media description
> grouping to indicate which m= lines that contains dependent media. And
> the a=depend SDP attribute links which RTP payload types in the
> respective media descriptions. There is no linking of the SSRCs. So
> when there is more than one SSRC with a given CNAME you have no other
> defined method than to use the same SSRC value across sessions.
> 
> Cheers
> 
> Magnus Westerlund
> 
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