publishAdditionalCodecForPublication method

Implementation

Future<void> publishAdditionalCodecForPublication(
  LocalTrackPublication publication,
  String backupCodec,
) async {
  if (publication.track is! LocalVideoTrack) {
    throw Exception('multi-codec simulcast is supported only for video');
  }
  final track = publication.track as LocalVideoTrack;

  final backupCodecOpts = publication.backupVideoCodec;
  if (backupCodecOpts == null) {
    throw Exception('backupCodec settings not specified');
  }

  var options = room.roomOptions.defaultVideoPublishOptions;
  options = options.copyWith(simulcast: backupCodecOpts.simulcast);

  if (backupCodec.toLowerCase() == publication.track?.codec?.toLowerCase()) {
    // not needed, same codec already published
    return;
  }

  if (backupCodec != backupCodecOpts.codec.toLowerCase()) {
    logger.warning(
      'requested a different codec than specified as backup serverRequested: ${backupCodec}, backup: ${backupCodecOpts.codec}',
    );
  }

  final encodings = Utils.computeTrackBackupEncodings(track, backupCodecOpts);
  if (encodings == null) {
    logger.fine('backup codec has been disabled, ignoring request to add additional codec for track');
    return;
  }

  final simulcastTrack = track.addSimulcastTrack(backupCodec, encodings);
  final dimensions = track.currentOptions.params.dimensions;

  final layers = Utils.computeVideoLayers(dimensions, encodings, isSVCCodec(backupCodec));

  simulcastTrack.sender = await room.engine.createSimulcastTransceiverSender(
    track,
    simulcastTrack,
    encodings,
    publication,
    backupCodec,
  );

  final cid = simulcastTrack.sender!.senderId;

  final req = lk_rtc.AddTrackRequest(
    cid: cid,
    name: options.name ??
        (track.source == TrackSource.screenShareVideo
            ? VideoPublishOptions.defaultScreenShareName
            : VideoPublishOptions.defaultCameraName),
    type: track.kind.toPBType(),
    source: track.source.toPBType(),
    muted: track.muted,
    layers: layers,
    sid: publication.sid,
    simulcastCodecs: <lk_rtc.SimulcastCodec>[
      lk_rtc.SimulcastCodec(
        codec: backupCodec.toLowerCase(),
        cid: cid,
      ),
    ],
  );

  // video specific
  if (dimensions.width > 0 && dimensions.height > 0) {
    req.width = dimensions.width;
    req.height = dimensions.height;
  }

  final trackInfo = await room.engine.addTrack(req);

  await room.engine.negotiate();

  logger.info('published backupCodec $backupCodec for track ${track.sid}, track info ${trackInfo}');
}