Re: [rtcweb] No Plan - SDP offer/answer clarification

"Roni Even" <ron.even.tlv@gmail.com> Mon, 03 June 2013 10:31 UTC

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From: "Roni Even" <ron.even.tlv@gmail.com>
To: "'Emil Ivov'" <emcho@jitsi.org>, <rtcweb@ietf.org>
Date: Mon, 3 Jun 2013 13:29:53 +0300
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Subject: Re: [rtcweb] No Plan - SDP offer/answer clarification
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Hi,
I read the draft and the email thread and I think I have similar questions
to the ones Cullen made.
My understanding was that the proposal is to  do one SDP offer/ answer
exchange  and add remove streams using other means (not specified)
I looked at the offer example is section 3 and it has 

a=max-send-ssrc:{*:1}                      // declaring maximum
   a=max-recv-ssrc:{*:4}                     // number of SSRCs

I have some clarifying questions?

1. Is the proposal to always offer max-send-ssrc=1?

2. What is the answer in this case can it be max-send-ssrc=4?

3. If max-send-ssrc >1 in the answer and the m-line has, for example,
support for H.264 and VP8 with max-send-ssrc=2  and de-multiplexing is based
on pt number, it will require four pt in the m-line since there can be two
VP8 or two H.264 RTP streams 

   m=video 5002 RTP/SAVPF 97 98 99 100
   a=mid:video
   a=rtcp-mux
   a=rtpmap:97 VP8/90000        
   a=rtpmap:98 VP8/90000        
   a=rtpmap:99 H264/90000
   a=rtpmap:100 H264/90000
Is my understanding correct?


Roni



> -----Original Message-----
> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On
> Behalf Of Emil Ivov
> Sent: 29 May, 2013 10:00 PM
> To: rtcweb@ietf.org
> Subject: [rtcweb] No Plan
> 
> Hey all,
> 
> Based on many of the discussions that we've had here, as well as many
> others that we've had offlist, it seemed like a good idea to investigate a
> negotiation alternative that relies on SDP and Offer/Answer just a little
bit
> less.
> 
> The following "no plan" draft attempts to present one such approach:
> 
> http://tools.ietf.org/html/draft-ivov-rtcweb-noplan
> 
> The draft relies on conventional use of SDP O/A but leaves the intricacies
of
> multi-source scenarios to application-specific signalling, with
potentially a
> little help from RTP.
> 
> Hopefully, proponents of Plans A and B would find that the
interoperability
> requirements that concerned them can still be met with "no plan". Of
course
> they would have to be addressed by application-specific signalling and/or
> signalling gateways.
> 
> Comments are welcome!
> 
> Cheers,
> Emil
> 
> --
> https://jitsi.org
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb