how to increase playback speed in iframe code example

Example: iframe video speed

function feAdjustVideoPlaybackInFrame(frame, playbackRate) {
  var i;
  for (i=0; i<frame.frames.length; i++) {
    try {
      feAdjustVideoPlaybackInFrame(frame.frames[i], playbackRate);
      frame.frames[i].document.querySelector('video').playbackRate = playbackRate;
    }
    catch(e) {};
  }
}
feAdjustVideoPlaybackInFrame(window, 1.5);