interceptor.js

} else if (responseType === 'arraybuffer') {
  //  The itag is a unique identifier which provides a 1:1 between videoInfo and a video data response.
  var itag = (responseURL.split('itag=')[1] || '').split('&')[0];

  //  There's no guarantee that the current request is a video data response.
  if (itag !== '') {
    var videoInfo = videoInfoList.filter(function(object) {
      return object.itag === itag;
    })[0];

    if (videoInfo) {
      //  Notify background of video information data necessary to render the video on another page.
      //  The type of video (including codec) as well as the ArrayBuffer of video data.
      var message = {
        buffer: this.response.slice(0),
        bufferType: videoInfo.type
      };

      //  Be sure to mark the buffer as transferable as it can be a large amount of data.
      window.top.postMessage(message, origin, [message.buffer]);
    }
  }
}