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Re: SDP renegotiation with same msid but different ssrc (video becomes frozen)

From: Iñaki Baz Castillo <ibc@aliax.net>
Date: Fri, 11 Mar 2016 14:55:55 +0100
Message-ID: <CALiegfk=YBU2yfxiFoiBUOWsc2YES1M801iLtHmUaxZv_EiVPg@mail.gmail.com>
To: Harald Alvestrand <harald@alvestrand.no>
Cc: "public-webrtc@w3.org" <public-webrtc@w3.org>
2016-03-11 14:48 GMT+01:00 Harald Alvestrand <harald@alvestrand.no>:
> I am not at all surprised it does not work. I think it should, but I'm
> not sure exactly how.

I'm strongly sure that this is 100% related:


Basically, when something changes in a MediaStream (added/removed
tracks) the video element rendering it is not updated. Setting again
video.src = URL.ObjectCreateURL(stream) updates it.

> Question: When does the sender change its SSRC to the new value? When
> sending the offer in the negotiation, or when getting the answer back
> that it's accepted?

Chrome sends a SDP re-offer. The SDP answer from the server contains
different ssrc than before the renegotiation.

> And what does it send inbetween those two times? Nothing, old SSRC or
> new SSRC?

Once the server receives the SDP re-offer from Chrome, the server
changes its sending ssrc and sends RTP packets with the new SSRC

Iñaki Baz Castillo
Received on Friday, 11 March 2016 13:56:42 UTC

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