Echo cancellation doesn't work

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

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Browser affected

Browser name including version (e.g. Chrome 64.0.3282.119) Chrome on MacOS: Version 78.0.3904.108 (Official Build) (64-bit) Actually I haven't got it work in any browser, either on Mac or PC.

Description

I am trying to use this sample for echo cancellation, but it doesn't work. https://webrtc.github.io/samples/src/content/getusermedia/record/

Steps to reproduce

1. On any laptop, unplug any headphone to make sure audio can play from speakers. (I am using a MBP)
2. Open https://webrtc.github.io/samples/src/content/getusermedia/record/ in Chrome, and check the "echo cancellation" box.
3. Start playing any YouTube in another Chrome tab. Make sure the audio is played from speaker.
4. Start to record video using this sample, accept any permissions for camera and microphone.

Expected results

I expect the recorded video should cancel the audio from YouTube significantly when the "echo cancellation" is checked.

Actual results

The audio from YouTube still got recorded and played back in original volume, regardless of whether "echo cancellation" is checked or not. I haven't made it work in any browser, either on Mac or PC.