Re: [webrtc-pc] WebRTC spec should explicitly specify all causes of a PeerConnection-sourced track being muted (#2915)

Here's https://jsfiddle.net/jib1/p6bzhme0/37/ showing what existing implementations fire on remote PC tracks. It opens a connection, and sender-side calls sender.track.stop() at the 3 second mark, and transceiver.stop() at 5.

Firefox:
```js
0.011: audio track event fired
0.011: video track event fired
0.011: sRD done.
0.016: checking
0.016: connected
0.043: video track unmute event fired
0.045: audio track unmute event fired
3.003: Stopped audio track
3.003: Stopped video track
5.006: Stopped audio transceiver
5.006: Stopped video transceiver
5.010: sRD done.
5.010: audio track ended event fired
5.010: video track ended event fired
```

Safari:
```js
0.016: audio track event fired
0.016: video track event fired
0.016: sRD done.
0.017: audio track unmute event fired
0.017: video track unmute event fired
0.023: checking
0.023: connected
3.001: Stopped audio track
3.001: Stopped video track
5.008: Stopped audio transceiver
5.008: Stopped video transceiver
5.016: audio track ended event fired
5.016: video track ended event fired
5.017: audio track mute event fired
5.017: video track mute event fired
5.017: sRD done.
```

Chrome:
```js
0.007: audio track event fired
0.007: video track event fired
0.007: audio track unmute event fired
0.007: video track unmute event fired
0.007: sRD done.
0.013: checking
0.017: connected
3.005: Stopped audio track
3.006: Stopped video track
4.196: video track mute event fired
5.003: Stopped audio transceiver
5.003: Stopped video transceiver
5.010: new
5.013: audio track ended event fired
5.013: video track ended event fired
5.014: sRD done.
```

Takeaways:
- Firefox appears to follow webrtc-pc's [ยง 9.3 MediaStreamTrack](https://w3c.github.io/webrtc-pc/#mediastreamtrack-network-use)
- Safari deviates by
  - unmuting after 1 ms, which is likely ahead of RTP reception (compared to 32 ms in Firefox)
  - muting tracks on stopped transceiver
- Chrome deviates by
  - unmuting ahead of sRD ([crbug 1295295](https://bugs.chromium.org/p/chromium/issues/detail?id=1295295))
  - muting (only!) video track after ~1 second ([crbug 941740](https://crbug.com/941740))

I did not try severing the network connection, but based on the above I would guess Chrome would mute the video track only.

Are there other causes of mute we should consider?

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Received on Wednesday, 17 January 2024 22:42:32 UTC