[webrtc-svc] What should the scalability mode be when the preferred scalability mode is not supported on the requested codec? (#59)

alvestrand has just created a new issue for https://github.com/w3c/webrtc-svc:

== What should the scalability mode be when the preferred scalability mode is not supported on the requested codec? ==
Consider the following code snippet:

```
  const pc1 = new RTCPeerConnection();
  const transceiver = pc1.addTransceiver(track1, {
    sendEncodings: [{ scalabilityMode: 'L3T3' }],
  });
  // Pick a codec known to not have L3T3 support
  const capabilities = RTCRtpSender.getCapabilities('video');
  console.log(JSON.stringify(capabilities.codecs, null, 2));
  const codec = capabilities.codecs.find(c => c.mimeType === 'video/VP8');
 ... negotiate ...
```
What should the result of getParameters.encodings.scalabilityMode be?

Possible alternatives:

- Missing or empty string, corresponding to "platform made its own choice"
- The scalability mode that the platform is actually using
- L3T3, becaue that's what the user requested

At the moment, Chrome chooses the third alternative.


Please view or discuss this issue at https://github.com/w3c/webrtc-svc/issues/59 using your GitHub account


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Received on Thursday, 6 January 2022 11:29:59 UTC