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Re: [rtcweb] JSEP question: How to set up simulcast for server-originated calls?

Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com> Tue, 06 November 2018 00:59 UTC

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To: Harald Alvestrand <harald@alvestrand.no>, Bernard Aboba <bernard.aboba@gmail.com>
Cc: RTCWeb IETF <rtcweb@ietf.org>
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From: Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com>
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Date: Tue, 06 Nov 2018 02:02:57 +0100
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Subject: Re: [rtcweb] JSEP question: How to set up simulcast for server-originated calls?
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On 06/11/2018 0:50, Harald Alvestrand wrote:
>> [BA] Most of the code examples I have seen that use addTrack for 
>> simulcast call setParameters prior to createOffer().  To allow this, 
>> we might consider saying that when addTrack returns, the encodings 
>> are initially null, and so can be set by setParameters().
>
> We could also allow the number of encodings to be changed in general, 
> with the proviso that if you increase the number, you have to inspect 
> the result to see how many you got (browser would drop extra elements).

IMHO the number of encodings should be allowed to be changed by 
setParameters (either for a transceiver started via addTrack or 
addTransceiver) until the corresponding m-line is negotiated by an SDP 
O/A (until it has a mid value?). Changing the number of encodings after 
that, I don't think it is allowed by the simulcast draft.

Best regards

Sergio

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