webrtc/RTCRtpTransceiver-setCodecPreferences.html

<!doctype html>
<meta charset=utf-8>
<meta name="variant" content="?interop-2026">
<meta name="variant" content="?rest">
<title>RTCRtpTransceiver.prototype.setCodecPreferences</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="./third_party/sdp/sdp.js"></script>
<script>
'use strict';
const rest = !new URLSearchParams(location.search).has("interop-2026");
const interop2026 = !new URLSearchParams(location.search).has("rest");

if (rest) {
  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('audio');
    transceiver.setCodecPreferences(capabilities.codecs);
  }, `setCodecPreferences() on audio transceiver with codecs returned from RTCRtpReceiver.getCapabilities('audio') should succeed`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('video');
    const capabilities = RTCRtpReceiver.getCapabilities('video');
    transceiver.setCodecPreferences(capabilities.codecs);
  }, `setCodecPreferences() on video transceiver with codecs returned from RTCRtpReceiver.getCapabilities('video') should succeed`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    transceiver.setCodecPreferences([]);
  }, `setCodecPreferences([]) should succeed`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('audio');
    const { codecs } = capabilities;

    if(codecs.length >= 2) {
      const tmp = codecs[0];
      codecs[0] = codecs[1];
      codecs[1] = tmp;
    }

    transceiver.setCodecPreferences(codecs);
  }, `setCodecPreferences() with reordered codecs should succeed`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('video');
    const capabilities = RTCRtpReceiver.getCapabilities('video');
    const { codecs } = capabilities;
    // This test verifies that the mandatory VP8 codec is present
    // and can be preferred.
    const codec = codecs.find(c => c.mimeType === 'video/VP8');
    assert_true(!!codec, 'VP8 video codec was found');
    transceiver.setCodecPreferences([codec]);
  }, `setCodecPreferences() with only VP8 should succeed`);
}

if (interop2026) {
  test(() => {
    const pc = new RTCPeerConnection();
    const transceiver = pc.addTransceiver('video');
    const capabilities = RTCRtpReceiver.getCapabilities('video');
    const { codecs } = capabilities;
    // This test verifies that the mandatory H264 codec is present
    // and can be preferred.
    const codec = codecs.find(c => c.mimeType === 'video/H264');
    assert_true(!!codec, 'H264 video codec was found');
    transceiver.setCodecPreferences([codec]);
  }, `setCodecPreferences() with only H264 should succeed`);
}

  async function getRTPMapLinesWithCodecAsFirst(firstCodec)
  {
     const codecs = RTCRtpReceiver.getCapabilities('video').codecs;
     codecs.forEach((codec, idx) => {
       if (codec.mimeType === firstCodec) {
        codecs.splice(idx, 1);
        codecs.unshift(codec);
       }
     });

     const pc = new RTCPeerConnection();
     const transceiver = pc.addTransceiver('video');
     transceiver.setCodecPreferences(codecs);
     const offer = await pc.createOffer();

     return offer.sdp.split('\r\n').filter(line => line.startsWith('a=rtpmap:'));
  }

if (interop2026) {
  promise_test(async () => {
    const lines = await getRTPMapLinesWithCodecAsFirst('video/H264');

    assert_greater_than(lines.length, 1);
    assert_true(lines[0].indexOf('H264') !== -1, 'H264 should be the first codec');
  }, `setCodecPreferences() should allow setting H264 as first codec`);
}

if (rest) {
  promise_test(async () => {
    const lines = await getRTPMapLinesWithCodecAsFirst('video/VP8');

    assert_greater_than(lines.length, 1);
    assert_true(lines[0].indexOf('VP8') !== -1, 'VP8 should be the first codec');
  }, `setCodecPreferences() should allow setting VP8 as first codec`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('video');
    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(capabilities.codecs));
  }, `setCodecPreferences() on audio transceiver with codecs returned from getCapabilities('video') should throw InvalidModificationError`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const codecs = [{
      mimeType: 'data',
      clockRate: 2000,
      channels: 2,
      sdpFmtpLine: '0-15'
    }];

    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(codecs));
  }, `setCodecPreferences() with user defined codec with invalid mimeType should throw InvalidModificationError`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const codecs = [{
      mimeType: 'audio/piepiper',
      clockRate: 2000,
      channels: 2,
      sdpFmtpLine: '0-15'
    }];

    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(codecs));
  }, `setCodecPreferences() with user defined codec should throw InvalidModificationError`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('audio');
    const codecs = [
      ...capabilities.codecs,
      {
        mimeType: 'audio/piepiper',
        clockRate: 2000,
        channels: 2,
        sdpFmtpLine: '0-15'
      }];

    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(codecs));
  }, `setCodecPreferences() with user defined codec together with codecs returned from getCapabilities() should throw InvalidModificationError`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('audio');
    const codecs = [capabilities.codecs[0]];
    codecs[0].clockRate = codecs[0].clockRate / 2;

    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(codecs));
  }, `setCodecPreferences() with modified codec clock rate should throw InvalidModificationError`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('audio');
    const codecs = [capabilities.codecs[0]];
    codecs[0].channels = codecs[0].channels + 11;

    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(codecs));
  }, `setCodecPreferences() with modified codec channel count should throw InvalidModificationError`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('audio');
    const codecs = [capabilities.codecs[0]];
    codecs[0].sdpFmtpLine = "modifiedparameter=1";

    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(codecs));
  }, `setCodecPreferences() with modified codec parameters should throw InvalidModificationError`);

  test((t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const capabilities = RTCRtpReceiver.getCapabilities('audio');

    const { codecs } = capabilities;
    assert_greater_than(codecs.length, 0,
      'Expect at least one codec available');

    const [ codec ] = codecs;
    const { channels=2 } = codec;
    codec.channels = channels+1;

    assert_throws_dom('InvalidModificationError', () => transceiver.setCodecPreferences(codecs));
  }, `setCodecPreferences() with modified codecs returned from getCapabilities() should throw InvalidModificationError`);

  promise_test(async (t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('audio');
    const {codecs} = RTCRtpReceiver.getCapabilities('audio');
    // Reorder codecs, put PCMU/PCMA first.
    let firstCodec;
    let i;
    for (i = 0; i < codecs.length; i++) {
      const codec = codecs[i];
      if (codec.mimeType === 'audio/PCMU' || codec.mimeType === 'audio/PCMA') {
        codecs.splice(i, 1);
        codecs.unshift(codec);
        firstCodec = codec.mimeType.substr(6);
        break;
      }
    }
    assert_not_equals(firstCodec, undefined, 'PCMU or PCMA codec not found');
    transceiver.setCodecPreferences(codecs);

    const offer = await pc.createOffer();
    const mediaSection = SDPUtils.getMediaSections(offer.sdp)[0];
    const rtpParameters = SDPUtils.parseRtpParameters(mediaSection);
    assert_equals(rtpParameters.codecs[0].name, firstCodec);
  }, `setCodecPreferences() modifies the order of audio codecs in createOffer`);
}

if (interop2026) {
  promise_test(async (t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const transceiver = pc.addTransceiver('video');
    const {codecs} = RTCRtpReceiver.getCapabilities('video');
    // Reorder codecs, swap H264 and VP8.
    let vp8 = -1;
    let h264 = -1;
    let firstCodec;
    let i;
    for (i = 0; i < codecs.length; i++) {
      const codec = codecs[i];
      if (codec.mimeType === 'video/VP8' && vp8 === -1) {
        vp8 = i;
        if (h264 !== -1) {
          codecs[vp8] = codecs[h264];
          codecs[h264] = codec;
          firstCodec = 'VP8';
          break;
        }
      }
      if (codec.mimeType === 'video/H264' && h264 === -1) {
        h264 = i;
        if (vp8 !== -1) {
          codecs[h264] = codecs[vp8];
          codecs[vp8] = codec;
          firstCodec = 'H264';
          break;
        }
      }
    }
    assert_not_equals(firstCodec, undefined, 'VP8 and H264 codecs not found');
    transceiver.setCodecPreferences(codecs);

    const offer = await pc.createOffer();
    const mediaSection = SDPUtils.getMediaSections(offer.sdp)[0];
    const rtpParameters = SDPUtils.parseRtpParameters(mediaSection);
    assert_equals(rtpParameters.codecs[0].name, firstCodec);
  }, `setCodecPreferences() modifies the order of video codecs in createOffer`);
}

  ['rtx', 'red', 'ulpfec'].forEach(resiliencyMechanism => {
    if (interop2026 && resiliencyMechanism != 'rtx') return;
    if (rest && resiliencyMechanism == 'rtx') return;
    promise_test(async (t) => {
      const pc = new RTCPeerConnection();
      t.add_cleanup(() => pc.close());
      const transceiver = pc.addTransceiver('video');
      const {codecs} = RTCRtpReceiver.getCapabilities('video');
      const filteredCodecs = codecs.
        filter(codec => codec.mimeType !== 'video/' + resiliencyMechanism);
      assert_not_equals(codecs.length, filteredCodecs.length);
      transceiver.setCodecPreferences(filteredCodecs);

      const offer = await pc.createOffer();
      const mediaSection = SDPUtils.getMediaSections(offer.sdp)[0];
      const rtpParameters = SDPUtils.parseRtpParameters(mediaSection);
      assert_equals(rtpParameters.codecs.find(codec => codec.name === resiliencyMechanism),
                    undefined);
    }, `setCodecPreferences() can remove ${resiliencyMechanism}`);
  });

if (interop2026) {
  // Tests the note removed as result of discussion in
  // https://github.com/w3c/webrtc-pc/issues/2933
  promise_test(async (t) => {
    const pc1 = new RTCPeerConnection();
    t.add_cleanup(() => pc1.close());
    const pc2 = new RTCPeerConnection();
    t.add_cleanup(() => pc2.close());

    const transceiver = pc1.addTransceiver('video');
    const {codecs} = RTCRtpReceiver.getCapabilities('video');
    const vp8 = codecs.find(codec => codec.mimeType === 'video/VP8');
    const h264 = codecs.find(codec => codec.mimeType === 'video/H264');
    const thirdCodec = codecs.find(codec => ['video/VP9', 'video/AV1'].includes(codec.mimeType));
    assert_true(!!vp8);
    assert_true(!!h264);
    assert_true(!!thirdCodec);

    transceiver.setCodecPreferences([vp8, thirdCodec]);
    await pc1.setLocalDescription();
    await pc2.setRemoteDescription(pc1.localDescription);
    const transceiver2 = pc2.getTransceivers()[0];
    transceiver2.setCodecPreferences([h264, thirdCodec, vp8]);
    await pc2.setLocalDescription();
    await pc1.setRemoteDescription(pc2.localDescription);
    const mediaSection = SDPUtils.getMediaSections(pc2.localDescription.sdp)[0];
    const rtpParameters = SDPUtils.parseRtpParameters(mediaSection);
    // Order is determined by pc2 but H264 is not present.
    assert_equals(rtpParameters.codecs.length, 2);
    assert_equals(rtpParameters.codecs[0].name, thirdCodec.mimeType.substring(6));
    assert_equals(rtpParameters.codecs[1].name, 'VP8');

  }, `setCodecPreferences() filters on receiver and prefers receiver order`);

  ["audio", "video"].forEach(kind => promise_test(async (t) => {
    const pc = new RTCPeerConnection();
    t.add_cleanup(() => pc.close());
    const [codec] = RTCRtpReceiver.getCapabilities(kind).codecs;
    codec.mimeType = codec.mimeType.toUpperCase();
    const transceiver = pc.addTransceiver(kind);
    transceiver.setCodecPreferences([codec]);

    codec.mimeType = codec.mimeType.toLowerCase();
    transceiver.setCodecPreferences([codec]);
  }, `setCodecPreferences should accept ${kind} codecs regardless of mimeType case`));
}

 </script>