sousa-gecko/testing/web-platform/tests/webrtc/RTCRtpEncodingParameters-codec-opus-stereo.https.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>RTCRtpEncodingParameters codec opus stereo</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
'use strict';

const kNumChannelsMono = 1;
const kNumChannelsStereo = 2;
const kAudioProcessingEnabled = true;
const kAudioProcessingDisabled = false;

// In some implementations (e.g. Chrome), whether or not audio processing is
// used may affect the number of channels we get.
// To isolate this factor from the test, we constrain both channels and APM.
function getAudioConstraints(numChannels, audioProcessing) {
  return {
    channelCount: {exact: numChannels},
    autoGainControl: audioProcessing,
    echoCancellation: audioProcessing,
    noiseSuppression: audioProcessing
  };
}

// Polls getSettings() until `channelCount` is known.
// Remote tracks don't populate their `channelCount` until media is received.
async function pollChannelCount(t, track) {
  while (true) {
    if (track.getSettings().channelCount != undefined) {
      break;
    }
    await new Promise(r => t.step_timeout(r, 50));
  }
  return track.getSettings().channelCount;
}

promise_test(async t => {
  const pc1 = new RTCPeerConnection();
  t.add_cleanup(() => pc1.close());
  const pc2 = new RTCPeerConnection();
  t.add_cleanup(() => pc2.close());
  pc1.onicecandidate = e => pc2.addIceCandidate(e.candidate);
  pc2.onicecandidate = e => pc1.addIceCandidate(e.candidate);

  // Open microphone as mono.
  const stream = await navigator.mediaDevices.getUserMedia(
      {audio: getAudioConstraints(kNumChannelsMono, kAudioProcessingEnabled)});
  const [track] = stream.getTracks();
  t.add_cleanup(() => track.stop());
  // Prerequisite of the test.
  assert_equals(track.getSettings().channelCount, 1,
                'Can open track in mono');

  // Negotiate opus.
  const transceiver = pc1.addTransceiver(track);
  transceiver.setCodecPreferences(
      RTCRtpSender.getCapabilities('audio').codecs.filter(
          codec => codec.mimeType == 'audio/opus'));
  await pc1.setLocalDescription();
  await pc2.setRemoteDescription(pc1.localDescription);
  await pc2.setLocalDescription();
  await pc1.setRemoteDescription(pc2.localDescription);

  const [receiver] = pc2.getReceivers();
  const remoteTrack = receiver.track;
  // Attaching the track to an audio element is needed for media to flow,
  // otherwise the `channelCount` is never known.
  const audio = document.createElement('audio');
  audio.srcObject = new MediaStream();
  audio.srcObject.addTrack(remoteTrack);
  // The stereo opus decoder outputs stereo regardless of the signal on the
  // wire.
  assert_equals(await pollChannelCount(t, remoteTrack), 2,
                'Remote track is stereo (despite local track being mono)');
}, 'Sending and receiving a mono track with opus (stereo decoder upmix)');

promise_test(async t => {
  const pc1 = new RTCPeerConnection();
  t.add_cleanup(() => pc1.close());
  const pc2 = new RTCPeerConnection();
  t.add_cleanup(() => pc2.close());
  pc1.onicecandidate = e => pc2.addIceCandidate(e.candidate);
  pc2.onicecandidate = e => pc1.addIceCandidate(e.candidate);

  // Open microphone as stereo.
  const stream = await navigator.mediaDevices.getUserMedia(
    {audio: getAudioConstraints(kNumChannelsStereo, kAudioProcessingDisabled)});
  const [track] = stream.getTracks();
  t.add_cleanup(() => track.stop());
  // Prerequisite of the test.
  assert_equals(track.getSettings().channelCount, 2,
                'Can open track in stereo');

  // Negotiate opus.
  const transceiver = pc1.addTransceiver(track);
  transceiver.setCodecPreferences(
      RTCRtpSender.getCapabilities('audio').codecs.filter(
          codec => codec.mimeType == 'audio/opus'));
  await pc1.setLocalDescription();
  await pc2.setRemoteDescription(pc1.localDescription);
  await pc2.setLocalDescription();
  await pc1.setRemoteDescription(pc2.localDescription);

  const [receiver] = pc2.getReceivers();
  const remoteTrack = receiver.track;
  // Attaching the track to an audio element is needed for media to flow,
  // otherwise the `channelCount` is never known.
  const audio = document.createElement('audio');
  audio.srcObject = new MediaStream();
  audio.srcObject.addTrack(remoteTrack);
  assert_equals(await pollChannelCount(t, remoteTrack), 2,
                'Remote track is also stereo');
}, 'Sending and receiving a stereo track with opus');
</script>