<?xml version="1.0" encoding="UTF-8"?>
<smil>
<body>
<switch>
  <video src="2160p.mp4" />
  <video src="1440p.mp4" />
  <video src="1080p.mp4" />
  <video src="720p.mp4" />
  <audio src="2160p.mp4" />
</switch>
</body>
</smil>
