function supports_video() {
  return !!document.createElement('video').canPlayType;
}
function supports_h264_baseline_video() {
  if (!supports_video()) { return false; }
  var v = document.createElement("video");
  var r=v.canPlayType('video/mp4; codecs="avc1.42E01E, mp4a.40.2"');
  return r == 'maybe' || r == 'probably';
}