Improving Screen share quality for an h264 video room that was VP8 before

Kaplan

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Oct 30, 2017, 9:19:29 AM10/30/17

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Hi Janusers,

I am experimenting with the new h264 support in Edge and iOS, so I moved my previously VP8 video room to be an H264 room and changed nothing else.

The screen-share quality is significantly worse than on the VP8 room, text looks blurry, and it takes a few seconds to become sharp, then when a new FIR is set, it goes blurry again, and so on and so for.

I have my Janus video room fir_rate at 5 , and my getUserMedia constrains to only do 1 frame per second (maxFrameRate:1, minFrameRate: 1) This with VP8 gives very sharp text and images. Not so with h264.

Does anybody have any suggestion on how to make h264 screen-share better? Is a fir_rate of 5 too low?

Any help appreciated.

Kaplan

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Oct 30, 2017, 9:06:09 PM10/30/17

to meetecho-janus

Hopefully this will help somebody. turns out I was screensharing from a mac, and long ago I had enabled a Chrome flag on it that messed the software h264 decoder/encoder (under chrome://flags), I just reset that flag and now screenshare looks nice on h264 as well as vp8.

thanks!

Lorenzo Miniero

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Oct 31, 2017, 5:49:51 AM10/31/17

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Thanks for sharing your findings, this will definitrly be helpful to many people with the same issue.

L.

Anil Wadghule

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Oct 31, 2017, 6:43:58 AM10/31/17

to Lorenzo Miniero, meetecho-janus

Thanks, Kaplan.

Are there any other tweaks in Janus or WebRTC to make screen sharing look as good as Screenhero?

I noticed that Screenhero is more clear and crisp when I do screen sharing with it. compared to my app with Janus.

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Best,

Anil

Lorenzo Miniero

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Oct 31, 2017, 7:25:10 AM10/31/17

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It's probably JavaScript tweaks on the client side (Janus is a server and never modifies the media, so it can't make it worse). Besides, AFAIK Screenhero uses Janus too.

L.

Kaplan

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Oct 31, 2017, 11:17:23 AM10/31/17

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Like Lorenzo said, what I found to help at least for my use case is to play with the constrains on janus.js

Look into using maxFrameRate: 1 , minFrameRate: 1 and also make sure your Janus Video Room has an ample bitrate, at least 512000 , but also try with 1024000.

If you are using Chrome to screen-share, look into the "goog" optional getUserMedia constrains, they have some interesting ones that Hangouts used for screensharing (google them ;).

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Best,
Anil

Mirko Brankovic

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Oct 31, 2017, 11:43:46 AM10/31/17

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Yeah, increasing the bitrate limit, to at least 2mbps is necessary if you want 1080HD image, and webrtc at least on chrome will try to maximize it to that value

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Regards,

Mirko

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