message: use mirrored source
diff: @@ -163,10 +163,8 @@ class ActiveSpeakerMultiplexer
  throw new Error("Track already added");
  //Get first encoding
  const encoding = track.encodings.values().next().value;
  - //Get first source
  - const source = encoding.mirror ? encoding.mirror : encoding.source;
  //Check source
  - if (!source)
  + if (!encoding.source)
  //Error
  throw new Error("Could not find source for track");
  @@ -177,7 +175,7 @@ class ActiveSpeakerMultiplexer
  this.ids.set(track,id);
  this.speakers.set(id,track);
  //Start listening to it
  - this.multiplexer.AddIncomingSourceGroup(source, id);
  + this.multiplexer.AddIncomingSourceGroup(encoding.source, id);
  //Singal track is attached
  track.attached();
  //Listen for stop events
  