Re: [rtcweb] Why is required to have local streams before running ICE gathering? (another SDP limitation?)
Eric Rescorla <ekr@rtfm.com> Thu, 13 June 2013 15:22 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 13 Jun 2013 08:21:12 -0700
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To: Iñaki Baz Castillo <ibc@aliax.net>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Why is required to have local streams before running ICE gathering? (another SDP limitation?)
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On Thu, Jun 13, 2013 at 7:55 AM, Iñaki Baz Castillo <ibc@aliax.net> wrote: > Hi, let me expose the following simple case: > > > 1) SIP application in the web. > > 2) Alice receives INVITE from Bob with audio and video. > > 3) Alice JS UA is ringing, Alice does not answer or reject the call yet. > > 4) Alice JS UA does not know whether Alice would answer with audio and/or > video. > > 5) Alice JS UA starts ICE gathering and obtains all its ICE candidates. > > 6) Alice presses "Answer with audio and video". > > 7) Alice JS UA calls getUserMedia, creates the PC, gets the SDP and > passes it to Bob JS UA in a SIP 200 response. > > > Well, this is not possible in WebRTC due to step 5. Unfortunately > before ICE gathering, the local PC must be set with the local SDP, so > getUserMedia is required to happen before ICE gathering. > I don't think that there is an intention that ICE gathering must not happen prior to setLocal: 1. There is agreement that there should be a mechanism to pre-specify the size of a candidate pool to gather, though I just glanced in the spec and I didn't see it. (May have missed it though). 2. Firefox, at least, gathers some candidates as soon as the PC is created, and I don't think this should be forbidden. (Though there is some disagreement about this.) > But we cannot prompt Alice with the getUserMedia pop-up while she has > not yet decided to answer the incoming call. > > The fact is that both the audio and video will use the same UDP > channel/transport, so having ICE candidates for the audio and the > video m lines is just unneeded. > > So IMHO this is another issue due to the usage of SDP, right? or may > be I am wrong? If so please let me know a use case in which the > browser would mantain two different UDP channels/transports for the > same "call" (a single SDP O/A). > It's not a matter of using SDP, it's a matter of being able to interop at all with endpoints which don't bundle. -Ekr
- [rtcweb] Why is required to have local streams be… Iñaki Baz Castillo
- Re: [rtcweb] Why is required to have local stream… Eric Rescorla
- Re: [rtcweb] Why is required to have local stream… Eric Rescorla
- Re: [rtcweb] Why is required to have local stream… Iñaki Baz Castillo
- Re: [rtcweb] Why is required to have local stream… Eric Rescorla
- Re: [rtcweb] Why is required to have local stream… Jim Barnett
- Re: [rtcweb] Why is required to have local stream… Justin Uberti
- Re: [rtcweb] Why is required to have local stream… Iñaki Baz Castillo