Re: [rtcweb] About unified Plan and multiple m lines

Eric Rescorla <ekr@rtfm.com> Wed, 24 July 2013 14:30 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 24 Jul 2013 07:29:01 -0700
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To: =?ISO-8859-1?Q?I=F1aki_Baz_Castillo?= <ibc@aliax.net>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] About unified Plan and multiple m lines
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On Wed, Jul 24, 2013 at 7:08 AM, Iñaki Baz Castillo <ibc@aliax.net> wrote:

> Hi, let's suppose WebRTC 1.0 borns with "Unified Plan" built-in, and
> my browser receives a session invitation from a conference server, and
> there are 8 audio participants in the conference.
>
> So the SDP I receive has 8 "m=audio" lines, maybe with different audio
> codecs in each line. And following SDP O/A rules my browser will
> generate SDP answer that will also contain 8 "m=audio" lines.
>
> Now, where it is supposed my browser will send my single audio track
> to the conference server? What does it mean that I receive 8 "m=audio"
> lines while I'm just able to send a single audio track? which m=audio
> line should I use for sending RTP?
>

One of them will be a=sendrecv. The others will be a=sendonly.
The sendrecv line is the one you use to send media.

-Ekr