how to play youtube 360 videos using vrview-web

I followed the instruction on http://ift.tt/2a97HjC to play 360 video on the web. Google's example video(http://ift.tt/2ejrsIM) works well. But I have difficulty to play youtube 360 videos or other mp4 files. How can I go through with it?

I tried to switch the value of is_stereo, but it didn't work. Someone says youTube 360 only supports mp4 of sizes up to 4096 on each axis. Therefore, the youtube video, I think, could be appropriate to vrview-web.

window.addEventListener('load', onVrViewLoad)
function onVrViewLoad() {
  var vrView = new VRView.Player('#vrview', {
    width: '100%',
    height: 600,
    video: 'https://www.youtube.com/embed/OkLa7jkFXpU',
    is_stereo: true
  });
}