[rtcweb] SDP is not suitable for WebRTC
Iñaki Baz Castillo <ibc@aliax.net> Mon, 29 July 2013 17:34 UTC
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From: Iñaki Baz Castillo <ibc@aliax.net>
Date: Mon, 29 Jul 2013 19:31:55 +0200
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To: "rtcweb@ietf.org" <rtcweb@ietf.org>, "public-webrtc@w3.org" <public-webrtc@w3.org>
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Subject: [rtcweb] SDP is not suitable for WebRTC
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Hi, I initiated a thread [*] about Plan-Unified and multiple m lines, but it was moved to MMUSIC maillist (don't know why since it is about WebRTC applications design): http://www.ietf.org/mail-archive/web/mmusic/current/msg11966.html Sorry for the cross-posting but at this point I'm a bit lost and do not know which is the appropriate group for my concern. So my concern is: - Web application with a SIP over WebSocket client running in the web. - The web user is provided with a conference SIP URI in which there are *already* 8 participants (5 of them emitting audio and video and 3 just emitting audio). - The user calls, from his webphone, to the given URI to join the conference. Let's imagine that the JS app knows the number of participant in the conference. Let's imagine my browser have mic and webcam. QUESTION: How can my browser join the conference without requiring SDP renegotiation from the server and, at the same time, being able to send audio/video and receive audio/video from others (different tracks / m=lines)? "SOLUTIONS": 1) I tell my browser to generate a SDP offer with: - 1 send/receive m=audio line. - 7 recvonly m=audio line. - 1 send/only m=video line. - 4 recvonly m=video line. (Obviously this is a joke) 2) SDP seems to allow that the offer and the answer have different number of m lines (I'm not aware of that but I believe that SDP can do "everything"). So my browser generates a SDP offer with 1 m=audio line and 1 m=video line, and the server replies with 8 m=audio lines and 4 m=video lines. Will my browser understand such a SDP answer with more m lines than its generated offer? I assume NOT. 3) My browser generates a SDP offer with 1 m=audio line and 1 m=video line and the server too. And later the server sends re-INVITE with all the m lines. Oppss, SDP renegotiation... SDP is bad for WebRTC. SDP is good for legacy symmetric communications in which there is a single-track audio communication and, of course, both endpoints emit audio. But SDP is bad for modern RTC protocols in which an endpoint can emit tons of tracks to a single endpoint. Do we really want this for WebRTC 1.0 ? -- Iñaki Baz Castillo <ibc@aliax.net>
- [rtcweb] SDP is not suitable for WebRTC Iñaki Baz Castillo
- Re: [rtcweb] SDP is not suitable for WebRTC piranna@gmail.com
- Re: [rtcweb] SDP is not suitable for WebRTC Bossiel thioriguel
- Re: [rtcweb] SDP is not suitable for WebRTC Iñaki Baz Castillo
- Re: [rtcweb] SDP is not suitable for WebRTC Silvia Pfeiffer
- Re: [rtcweb] SDP is not suitable for WebRTC Ron
- Re: [rtcweb] SDP is not suitable for WebRTC Christer Holmberg
- Re: [rtcweb] SDP is not suitable for WebRTC Iñaki Baz Castillo
- Re: [rtcweb] SDP is not suitable for WebRTC Iñaki Baz Castillo
- Re: [rtcweb] SDP is not suitable for WebRTC Christer Holmberg
- Re: [rtcweb] SDP is not suitable for WebRTC Iñaki Baz Castillo
- Re: [rtcweb] SDP is not suitable for WebRTC (UNCL… Roy, Radhika R CIV USARMY (US)