Use javascript to detect if an MP4 video has a sound track

Question

I am creating a custom controller for MP4 video on a web page. The controller includes a volume slider. Some of the videos that are to be played have no sound track. It would be

Answer 1

There might be a better way of doing this, although it's fairly simple just using regular javascript for webkit or mozilla enabled browsers. webkit utilizes this.audioTracks and mozilla uses this.mozHasAudio respectively:

document.getElementById("video").addEventListener("loadeddata", function() {
  if ('WebkitAppearance' in document.documentElement.style)
    var hasAudioTrack = this.audioTracks.length;
  else if (this.mozHasAudio)
    var hasAudioTrack = 1;
  if (hasAudioTrack > 0)
    alert("audio track detected");
  else
    alert("audio track not detected");
});

_{There's also a function this.webkitAudioDecodedByteCount, however, I've never had any luck making it work.}