CaptureStream/mozCaptureStream problem in video-to-peerconnection sample

[Sida63]

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• [ x ] I have provided steps to reproduce
• [ x ] I have provided browser name and version
• [ x ] I have provided a link to the sample here or a modified version thereof

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Browser affected

Firefox Browser name including version (e.g. Chrome 64.0.3282.119) Firefox 83.0 (64-bit)

Description

I use the CaptureStream/mozCaptureStream to capture video steam for video-to-peerconnection target in Chrome/Firefox. However, I noticed that when using mozCaptureStream in Fireforx, the video which is consumed by mozCpatureStream will lose it's sound output. I also give a test in Chrome and there is no such problem.

Steps to reproduce

The sample you post on the website is actually having same problem. Here are reproduce steps:

sample link: https://webrtc.github.io/samples/src/content/capture/video-pc/

1. Open the link in Firefox
2. Click the right video's mute button to mute the right video

Expected results

You should still hear the sound from the webpage you opened since only the video on the right side is muted. The result in Chrome is expected.

Actual results

No sound can be heard from the webpage.

[eyaler]

having the same issue. i think this is the culprit: https://bugzilla-dev.allizom.org/show_bug.cgi?id=1178751