How to enable chrome to send 4 simulcast streams instead of only 3

[Prashant Laheri]

Hi Folks,

I am encoding the 4 simulcast streams like below but chrome sends only 3.

How to enable chrome/browser to send 4 simulcast streams without reducing the count to 3?

chrome Debug Logs:

[22568:29187:1124/001230.930248:WARNING:simulcast.cc(242)] Reducing simulcast layer count from 4 to 3
[22568:29187:1124/001230.930348:INFO:video_stream_encoder.cc(724)] ReconfigureEncoder:
Simulcast streams:
0: 160x90 fps: 15 min_kbps: 30 target_kbps: 99 max_kbps: 120 max_fps: 15 max_qp: 56 num_tl: 2 active: true
1: 320x180 fps: 30 min_kbps: 150 target_kbps: 272 max_kbps: 272 max_fps: 30 max_qp: 56 num_tl: 2 active: true
2: 640x360 fps: 30 min_kbps: 600 target_kbps: 640 max_kbps: 640 max_fps: 30 max_qp: 56 num_tl: 2 active: true

From application SDK I am encoding like below:

this.simulcast = new Simulcast({numOfLayers: 4});
...

var videoSender = self.pc.getSenders().find(function(stream){return stream.track.kind === "video";});

var parameters = videoSender.getParameters();

//90p

                            parameters.encodings[0].maxBitrate = browserMediaConfig.profile90p.maxBitrate;

                            parameters.encodings[0].maxFramerate = browserMediaConfig.profile90p.maxFramerate;

                            parameters.encodings[0].scaleResolutionDownBy = browserMediaConfig.profile90p.scaleResolutionDownBy;

                            parameters.encodings[0].scalabilityMode = 'L1T3';

                            //180p

                            parameters.encodings[1].maxBitrate = browserMediaConfig.profile180p.maxBitrate;

                            parameters.encodings[1].maxFramerate = browserMediaConfig.profile180p.maxFramerate;

                            parameters.encodings[1].scaleResolutionDownBy = browserMediaConfig.profile180p.scaleResolutionDownBy;

                            parameters.encodings[1].scalabilityMode = 'L1T3';

                            // 360p

                            parameters.encodings[2].maxBitrate = browserMediaConfig.profile360p.maxBitrate;

                            parameters.encodings[2].maxFramerate = browserMediaConfig.profile360p.maxFramerate;

                            parameters.encodings[2].scaleResolutionDownBy = browserMediaConfig.profile360p.scaleResolutionDownBy;

                            parameters.encodings[2].scalabilityMode = 'L1T3';

                            // 720p

                            parameters.encodings[3].maxBitrate = browserMediaConfig.profile720p.maxBitrate;

                            parameters.encodings[3].maxFramerate = browserMediaConfig.profile720p.maxFramerate;

                            parameters.encodings[3].scalabilityMode = 'L1T3';

Note: We use VP8, so is there any restriction to send only 3 simulcast streams?

Thanks,

Prashant Laheri

[Prashant Laheri]

Hi Team,

Does anyone have any idea on this limitation of chromium?

Thanks,

Prashant Laheri

[Florent Castelli]

This is not supported by Chrome at the moment and the hard limit is 3 simulcast streams.

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[Roman Lakhtadyr]

Does Chrome or Chromium support disabling/enabling simulcasting layers on the fly?

[Philipp Hancke]

it does, https://webrtchacks.com/suspending-simulcast-streams/ is a pretty good description

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