コード
<video width="480" height="272" controls autobuffer>
<source type="video/mp4" src="xxx.mp4">
<source type="video/mp4" src="xxx.mp4">
<source type="video/ogv" src="xxx.ogv">
<source type="video/webm" src="xxx.webm">
<source type="video/flv" src="xxx.flv">
</video>