title: html5 audio. How to get bitrate
body: <p>I'm writing an extension for google chrome. And I have a situation: I've got a link for mp3 file, and I could play it. I could extract duration of it..</p>
  
  <p>But how could I calculate bitrate? Is it possible through some properties? Or through some calculations using file size? If second - how to get filesize?</p>
  
  <p>Thanks.</p>