Pseudo-code for listening to in-band ID3 tags when client-side ads may be active.

ads-and-id3.js

var id3Track = null;

// Step 1: listen for in-band metadata tracks to become available for new videos and 
// register your listeners
player.on('loadedmetadata', function() {
  for (var i = 0; i < player.textTracks().length; i++) {
    var track = player.textTracks()[i];

    if (track.inBandMetadataTrackDispatchType) {
      id3Track = track;
      id3Track.mode = 'hidden';
      id3Track.addEventListener('cuechange', handleCueChange);
    }
  }
});

// step 2: when the video starts playing, find the new id3 track if ads caused the
// old one to be replaced
player.on('playing', function() {
  for (var i = 0; i < player.textTracks().length; i++) {
    var track = player.textTracks()[i];
    
    if (track.inBandMetadataTrackDispatchType && 
        track !== id3track) {
      id3Track = track;
      id3Track.mode = 'hidden';
      id3Track.addEventListener('cuechange', handleCueChange);
    }
  }
});