servo/tests/wpt/web-platform-tests/webrtc/simulcast/simulcast.js

'use strict';
/* Helper functions to munge SDP and split the sending track into
 * separate tracks on the receiving end. This can be done in a number
 * of ways, the one used here uses the fact that the MID and RID header
 * extensions which are used for packet routing share the same wire
 * format. The receiver interprets the rids from the sender as mids
 * which allows receiving the different spatial resolutions on separate
 * m-lines and tracks.
 */

const ridExtensions = [
  "urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id",
  "urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id",
];

function ridToMid(description, rids) {
  const sections = SDPUtils.splitSections(description.sdp);
  const dtls = SDPUtils.getDtlsParameters(sections[1], sections[0]);
  const ice = SDPUtils.getIceParameters(sections[1], sections[0]);
  const rtpParameters = SDPUtils.parseRtpParameters(sections[1]);
  const setupValue = description.sdp.match(/a=setup:(.*)/)[1];
  const directionValue =
    sections[1].match(/a=sendrecv|a=sendonly|a=recvonly|a=inactive/)[0];
  const mline = SDPUtils.parseMLine(sections[1]);

  // Skip mid extension; we are replacing it with the rid extmap
  rtpParameters.headerExtensions = rtpParameters.headerExtensions.filter(
    ext => ext.uri != "urn:ietf:params:rtp-hdrext:sdes:mid"
  );

  for (const ext of rtpParameters.headerExtensions) {
    if (ext.uri == "urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id") {
      ext.uri = "urn:ietf:params:rtp-hdrext:sdes:mid";
    }
  }

  // Filter rtx as we have no way to (re)interpret rrid.
  // Not doing this makes probing use RTX, it's not understood and ramp-up is slower.
  rtpParameters.codecs = rtpParameters.codecs.filter(c => c.name.toUpperCase() !== 'RTX');

  if (!rids) {
    rids = Array.from(description.sdp.matchAll(/a=rid:(.*) send/g)).map(r => r[1]);
  }

  let sdp = SDPUtils.writeSessionBoilerplate() +
    SDPUtils.writeDtlsParameters(dtls, setupValue) +
    SDPUtils.writeIceParameters(ice) +
    'a=group:BUNDLE ' + rids.join(' ') + '\r\n';
  const baseRtpDescription = SDPUtils.writeRtpDescription(mline.kind, rtpParameters);
  for (const rid of rids) {
    sdp += baseRtpDescription +
        'a=mid:' + rid + '\r\n' +
        'a=msid:rid-' + rid + ' rid-' + rid + '\r\n';
    sdp += directionValue + "\r\n";
  }
  return sdp;
}

function midToRid(description, localDescription, rids) {
  const sections = SDPUtils.splitSections(description.sdp);
  const dtls = SDPUtils.getDtlsParameters(sections[1], sections[0]);
  const ice = SDPUtils.getIceParameters(sections[1], sections[0]);
  const rtpParameters = SDPUtils.parseRtpParameters(sections[1]);
  const setupValue = description.sdp.match(/a=setup:(.*)/)[1];
  const directionValue =
    sections[1].match(/a=sendrecv|a=sendonly|a=recvonly|a=inactive/)[0];
  const mline = SDPUtils.parseMLine(sections[1]);

  // Skip rid extensions; we are replacing them with the mid extmap
  rtpParameters.headerExtensions = rtpParameters.headerExtensions.filter(
    ext => !ridExtensions.includes(ext.uri)
  );

  for (const ext of rtpParameters.headerExtensions) {
    if (ext.uri == "urn:ietf:params:rtp-hdrext:sdes:mid") {
      ext.uri = "urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id";
    }
  }

  const localMid = localDescription ? SDPUtils.getMid(SDPUtils.splitSections(localDescription.sdp)[1]) : "0";

  if (!rids) {
    rids = [];
    for (let i = 1; i < sections.length; i++) {
      rids.push(SDPUtils.getMid(sections[i]));
    }
  }

  let sdp = SDPUtils.writeSessionBoilerplate() +
    SDPUtils.writeDtlsParameters(dtls, setupValue) +
    SDPUtils.writeIceParameters(ice) +
    'a=group:BUNDLE ' + localMid + '\r\n';
  sdp += SDPUtils.writeRtpDescription(mline.kind, rtpParameters);
  // Although we are converting mids to rids, we still need a mid.
  // The first one will be consistent with trickle ICE candidates.
  sdp += 'a=mid:' + localMid + '\r\n';
  sdp += directionValue + "\r\n";

  for (const rid of rids) {
    const stringrid = String(rid); // allow integers
    const choices = stringrid.split(",");
    choices.forEach(choice => {
      sdp += 'a=rid:' + choice + ' recv\r\n';
    });
  }
  if (rids.length) {
    sdp += 'a=simulcast:recv ' + rids.join(';') + '\r\n';
  }

  return sdp;
}

async function doOfferToSendSimulcast(offerer, answerer) {
  await offerer.setLocalDescription();

  // Is this a renegotiation? If so, we cannot remove (or reorder!) any mids,
  // even if some rids have been removed or reordered.
  let mids = [];
  if (answerer.localDescription) {
    // Renegotiation. Mids must be the same as before, because renegotiation
    // can never remove or reorder mids, nor can it expand the simulcast
    // envelope.
    mids = [...answerer.localDescription.sdp.matchAll(/a=mid:(.*)/g)].map(
      e => e[1]
    );
  } else {
    // First negotiation; the mids will be exactly the same as the rids
    const simulcastAttr = offerer.localDescription.sdp.match(
      /a=simulcast:send (.*)/
    );
    if (simulcastAttr) {
      mids = simulcastAttr[1].split(";");
    }
  }

  const nonSimulcastOffer = ridToMid(offerer.localDescription, mids);
  await answerer.setRemoteDescription({
    type: "offer",
    sdp: nonSimulcastOffer,
  });
}

async function doAnswerToRecvSimulcast(offerer, answerer, rids) {
  await answerer.setLocalDescription();
  const simulcastAnswer = midToRid(
    answerer.localDescription,
    offerer.localDescription,
    rids
  );
  await offerer.setRemoteDescription({ type: "answer", sdp: simulcastAnswer });
}

async function doOfferToRecvSimulcast(offerer, answerer, rids) {
  await offerer.setLocalDescription();
  const simulcastOffer = midToRid(
    offerer.localDescription,
    answerer.localDescription,
    rids
  );
  await answerer.setRemoteDescription({ type: "offer", sdp: simulcastOffer });
}

async function doAnswerToSendSimulcast(offerer, answerer) {
  await answerer.setLocalDescription();

  // See which mids the offerer had; it will barf if we remove or reorder them
  const mids = [...offerer.localDescription.sdp.matchAll(/a=mid:(.*)/g)].map(
    e => e[1]
  );

  const nonSimulcastAnswer = ridToMid(answerer.localDescription, mids);
  await offerer.setRemoteDescription({
    type: "answer",
    sdp: nonSimulcastAnswer,
  });
}

async function doOfferToSendSimulcastAndAnswer(offerer, answerer, rids) {
  await doOfferToSendSimulcast(offerer, answerer);
  await doAnswerToRecvSimulcast(offerer, answerer, rids);
}

async function doOfferToRecvSimulcastAndAnswer(offerer, answerer, rids) {
  await doOfferToRecvSimulcast(offerer, answerer, rids);
  await doAnswerToSendSimulcast(offerer, answerer);
}

function swapRidAndMidExtensionsInSimulcastOffer(offer, rids) {
  return ridToMid(offer, rids);
}

function swapRidAndMidExtensionsInSimulcastAnswer(answer, localDescription, rids) {
  return midToRid(answer, localDescription, rids);
}

async function negotiateSimulcastAndWaitForVideo(
    t, rids, pc1, pc2, codec, scalabilityMode = undefined) {
  exchangeIceCandidates(pc1, pc2);

  const metadataToBeLoaded = [];
  pc2.ontrack = (e) => {
    const stream = e.streams[0];
    const v = document.createElement('video');
    v.autoplay = true;
    v.srcObject = stream;
    v.id = stream.id
    metadataToBeLoaded.push(new Promise((resolve) => {
        v.addEventListener('loadedmetadata', () => {
            resolve();
        });
    }));
  };

  const sendEncodings = rids.map(rid => ({rid}));
  // Use a 2X downscale factor between each layer. To improve ramp-up time, the
  // top layer is scaled down by a factor 2. Smaller layer comes first. For
  // example if MediaStreamTrack is 720p and we want to send three layers we'll
  // get {90p, 180p, 360p}.
  let scaleResolutionDownBy = 2;
  for (let i = sendEncodings.length - 1; i >= 0; --i) {
    if (scalabilityMode) {
      sendEncodings[i].scalabilityMode = scalabilityMode;
    }
    sendEncodings[i].scaleResolutionDownBy = scaleResolutionDownBy;
    scaleResolutionDownBy *= 2;
  }

  // Use getUserMedia as getNoiseStream does not have enough entropy to ramp-up.
  await setMediaPermission();
  const stream = await navigator.mediaDevices.getUserMedia({video: {width: 1280, height: 720}});
  t.add_cleanup(() => stream.getTracks().forEach(track => track.stop()));
  const transceiver = pc1.addTransceiver(stream.getVideoTracks()[0], {
    streams: [stream],
    sendEncodings: sendEncodings,
  });
  if (codec) {
    preferCodec(transceiver, codec.mimeType, codec.sdpFmtpLine);
  }

  const offer = await pc1.createOffer();
  await pc1.setLocalDescription(offer),
  await pc2.setRemoteDescription({
    type: 'offer',
    sdp: swapRidAndMidExtensionsInSimulcastOffer(offer, rids),
  });
  const answer = await pc2.createAnswer();
  await pc2.setLocalDescription(answer);
  await pc1.setRemoteDescription({
    type: 'answer',
    sdp: swapRidAndMidExtensionsInSimulcastAnswer(answer, pc1.localDescription, rids),
  });
  assert_equals(metadataToBeLoaded.length, rids.length);
  return Promise.all(metadataToBeLoaded);
}