title: Delivering video across all browsers
body: <p>I have a source video. In order to play it in all major browsers (IE7+, Chrome, Safari, Firefox), how many formats do I need to convert the video to? Will using a single .mp4 file be sufficient? What exactly is the <code>webm</code> format, and is it required that I additionally convert my video to this?</p>
  
  <p>In addition, what are some open source video players that would be able to play this format(s) in all browsers?</p>