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Re: [rtcweb] Proposal for a JS API for NoPlan (adding multiple sources without encoding them in SDP)

Emil Ivov <emcho@jitsi.org> Tue, 18 June 2013 06:17 UTC

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Date: Tue, 18 Jun 2013 08:17:09 +0200
From: Emil Ivov <emcho@jitsi.org>
Organization: Jitsi
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To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
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Cc: "<rtcweb@ietf.org>" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Proposal for a JS API for NoPlan (adding multiple sources without encoding them in SDP)
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Hey Silvia,

On 18.06.13, 03:00, Silvia Pfeiffer wrote:
> What I would like to see, though, is a bit different from what you've
> proposed. In particular, the MediaFlowDescription object is the one
> object that I believe is supposed to enable JS developers to  do "SDP
> hacking" without having to understand SDP. Unfortunately, the way in
> which it is currently written, this API doesn't help a JS developer
> much. There are properties in that object like "ssrc" that mean
> nothing unless you understand SDP.

SSRC is really just a flow identifier and it actually comes from RTP, 
not SDP.

Using SSRCs is important because they are the only way to refer to an 
RTP flow. Any other identifier (such as an MSID) would have to be mapped 
to an SSRC. Such a mapping could only happen in SDP and would have to be 
updated when new streams are added which brings us back to over-reliance 
on SDP Offer/Answer, which is what No Plan is trying to alleviate.

Emil

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