Re: [rtcweb] No Plan - SDP offer/answer clarification
Emil Ivov <emcho@jitsi.org> Tue, 04 June 2013 16:13 UTC
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Date: Tue, 04 Jun 2013 15:09:01 +0300
From: Emil Ivov <emcho@jitsi.org>
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To: Roni Even <ron.even.tlv@gmail.com>
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Subject: Re: [rtcweb] No Plan - SDP offer/answer clarification
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Hey Roni, On 04.06.13, 01:05, Roni Even wrote: > Hi Emil, > My understanding is that you propose to de-multiplex by the pt number so you > cannot have two rtp streams with the same payload type number A PT number is only used to pick a codec/processing chain. Different SSRCs would then be used as an indication that packets belong to different RTP flows and that they have to end-up in different MediaStream-s and eventually <video> tags. This works with No Plan and it does not require that SSRCs be known in advance. Does this answer your question? Emil > Roni > >> -----Original Message----- >> From: Emil Ivov [mailto:emcho@jitsi.org] >> Sent: 03 June, 2013 1:46 PM >> To: Roni Even >> Cc: rtcweb@ietf.org >> Subject: Re: [rtcweb] No Plan - SDP offer/answer clarification >> >> Hey Roni, >> >> On 03.06.13, 13:29, Roni Even wrote: >>> 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) >> >> Yes, this is exactly it. >> >>> 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? >> >> The max-ssrc in the SDP was just an example for capabilities that the > offerer >> could add to SDP (could be useful for mobile devices for example). It is > by no >> means essential to the approach. >> >>> 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? >> >> Can you help me understand why you need the PT duplication? Is this just > so >> that you could understand distinguish between two sources? If so, then it >> wouldn't be necessary. >> >> With No Plan you would just send: >> >> m=video 5002 RTP/SAVPF 97 99 >> a=mid:video >> a=rtcp-mux >> a=rtpmap:97 VP8/90000 >> a=rtpmap:99 H264/90000 >> >> If then you want to have one of the VP8 streams rendered on the left > screen >> and the other on the right, you will add this in application-specific > signalling. A >> web application could do this like this: >> >> { >> "leftSSRC": "1234", >> "rightSSRC": "5678" >> } >> >> An WebRTC-to-SIP gateway could transform this into SDP or whatever that >> target devices need. >> >> Does this answer your question? >> >> Emil >> >> >> >>> >>> >>> 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 >>> >>> >> >> -- >> https://jitsi.org > > -- https://jitsi.org
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Roni Even
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Emil Ivov
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Emil Ivov
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Roni Even
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Emil Ivov
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Roni Even
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Bernard Aboba
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Roni Even
- Re: [rtcweb] No Plan - SDP offer/answer clarifica… Mary Barnes