（ANCC,HTML5）How to detect browser support（video,audio）.

video,Ogg，MPEG 4，WebM

video，Ogg，MP3，Wav。

Different browsers use different types.

Hope to detect the type supported by the current browser,
Automatic playback to this type of file.

How the code is written in ANcc html5.

For example：  

<audio controls="controls">
  <source src="song.ogg" type="audio/ogg">
  <source src="song.mp3" type="audio/mpeg">
Your browser does not support the audio tag.
</audio>