Subject: [avtext] qusetions on draft-westerlund-avtext-rtcp-sdes-srcname-00

From: Roni Even <[email-masked]>
Date: Wed, 16 Nov 2011 07:47:08 +0200

Hi,

I read the draft and I am not sure I fully understand the mechanism so there
are clarification questions

Looking at the examples in section 5.1 through 5.4 it looks to me that the
offer has one RTP payload type number that is being used to send two video
streams with the same parameters. I was expecting to see two payload type
numbers that will allow separate a=fmtp lines for each of the streams.
Having both with the same functionality is limiting. Looking at 5.1 I see
for example two streams (SSRCs 192392452 and 834753488)having mid=2 with the
same capability so I assume that they may come from two cameras for example.
How do you know which is from which camera, will there be another a:ssrc
parameter. It is also limited since it assumes that both have the same video
capabilities

I am also not sure how does it work without the SDP.  If a receiver receives
two SDES for two SSRCs with the same srcname how does he know which one is
each without getting the mapping from the SDP, like in 5.1 how does a
receiver know if this is the mid=2 or 3 stream, is it based on RTP session
multiplexing. From the current text I get it this is intended for SSRC
multiplexing but to associate streams that can be identified either by the
RTP session or by the payload like in 5.3.

Roni