[jitsi-dev] Thanks for your reply, and one more SDP question about Jitsi.


#1

Hi George and Jitsi Experts,

Thanks for your time and help, sorry I don't know how to reply to the email
thread, but I attached the previous email below.

Hmm, when I checked the chrome://webrtc-internal, I saw 2 sets of creating
SDP.
2 * (setRemoteDescription -> createAnswerOnSuccess -> setLocalDescription),
in case of simulcast, does that mean Jicofo or Jitsi-Meet is sending 2 SDPs?

Also, I saw "a=ssrc-group:SIM" in the first set of setLocalDescription,
and in the second set, I saw that in both "createAnswerOnSuccess" and
"setLocalDescription", and that makes me confused...

And, could you please tell me the negotiation steps in case of Jitsi-Meet?
I have my own application, which call flow is: "createOffer ->
createOfferOnSuccess -> setLocalDescription -> setRemoteDescription"...

Thanks so much again~ :stuck_out_tongue:

Best,
Yisheng

Message: 2
Date: Fri, 11 Dec 2015 16:22:31 -0600
From: George Politis <gp@jitsi.org>
To: Jitsi Developers <dev@jitsi.org>
Subject: Re: [jitsi-dev] Having questions about SDP(s) sent to video
       bridge when simulcast.
Message-ID: <20151211222205.GA22587@localhost.localdomain>
Content-Type: text/plain; charset=us-ascii

Hi Yisheng,

Hi Experts,

I have a question about how many SDPs Chrome sends to the video bridge in
case of simulcast?

Enabling simulcast doesn't change the negotiation steps.

And I don't see in the setLocal/RemoteDescription set any max-fs for

frame

···

On Fri, Dec 11, 2015 at 05:03:14PM -0500, Yisheng Yang wrote:

size/resolution, do we set it anywhere else?

max-fs is not used in Chrome simulcast signaling nor in COLIBRI
simulcast signaling (which follows closely the Chrome simulcast
signaling).

If it sends two SDPs, do the two specify one for large resolution video
while the other specifies the small resolution video?

The simulcast formats are hardcoded into the webrtc.org enine so you
don't have much control over the actual resolutions, but they're
reasonably chosen. Also, we have recently updated the simulcast
documentation, you might want to have a look at that
https://github.com/jitsi/jitsi-videobridge/blob/master/doc/simulcast.md.

Best,
George

Best,
Yisheng

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