Re: [rtcweb] No Plan

Paul Kyzivat <> Thu, 30 May 2013 16:53 UTC

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Date: Thu, 30 May 2013 12:53:52 -0400
From: Paul Kyzivat <>
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Subject: Re: [rtcweb] No Plan
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On 5/30/13 11:53 AM, Enrico Marocco wrote:
> On 5/30/13 5:14 PM, Paul Kyzivat wrote:
>>> 1. sender gets the additional local tracks
>>> 2. sender tells the receiver on the app-specific signalling channel
>>>      (assuming a plain-english-over-something one): "I can also send you
>>>      video and audio of a webcam I've just installed in the girls locker
>>>      room. They'll have SSRC xxx and yyy" (xxx and yyy retrieved through
>>>      JS API -- kind of what exists in Chrome today for stats)
>>> 3. receiver responds "Shoot!"
>> What does the receiver say if it can use the media, but cannot receive
>> it over the *existing* audio and video m-lines where it is receiving
>> other media already?
> I may have misinterpreted the draft, but it seems to me the whole point
> here is about having WebRTC endpoints support multiple SSRCs on the same
> m-line. If that's the case, an endpoint not supporting that would
> qualify as "legacy". It would be behind a gateway anyway, and the
> gateway function would be in the best position to translate both SDP and
> media in a way it can digest.

"legacy" and "decomposed" are not the same thing.

Presumably the design center for webrtc is a browser running on one 
system with a single display. And in that case everything to a single 
address makes sense.

But consider webrtc in the context of clue/telepresence. A browser be a 
very good basis for a controller for a telepresence room - providing the 
UI for managing a telepresence system. But that room will also have 
multiple displays. Each may have its own rendering hw.

Or, if that is too extreme for you, consider a simple PC running a 
browser and connecting to a telepresence room. The PC may be putting 
several video streams into windows, and be happy to get them on a single 
address/port. But the *other* end may be a sip-based clue system, 
decomposed, that can't group all of the streams into a single bundle. 
This is not a *legacy* case - we are still designing clue.