HTML5 Video and degradation?

I've been playing around with the HTML5 video tag and I'm puzzled as to how best to degrade when you can't support a codec?

For older browsers (or IE) that don't support the video tag at all this quite is straight forward:

<video width="320" height="240">
  <source src="vid.ogv" type='video/ogg'>
  <source src="vid.mp4" type='video/mp4'>
  <object>
  <!-- Embed Flash video here to play mp4 -->
  <object>
</video>

They will fall through and will receive the Flash version (or other alternate such as an image!)

How about when the browser does support the tag but not the codec - Like FireFox 3.5 for example - and I can't support OGG (possibly because I already have vast archives of H.264):

<video width="320" height="240">
  <source src="vid.mp4" type='video/mp4'>
  <object>
  <!-- Embed Flash video here to play mp4 -->
  <object>
</video>

All I get in FireFox 3.5 is a grey box with an x in it. This isn't exactly a great user experience for FireFox users! I can only think of using JavaScript to check for FF3.5 and change the DOM!! is this really the bad old all over again! ...o开发者_StackOverflow中文版r is there some part of the spec I'm missing out on like a 'novideo' tag?

An important part of graceful degradation is the querying capabilities... Dive into HTML5 is a great read... specifically, look at the video section. Relevant code here:

function supports_h264_baseline_video() {
  if (!supports_video()) { return false; }
  var v = document.createElement("video");
  return v.canPlayType('video/mp4; codecs="avc1.42E01E, mp4a.40.2"');
}

Note: this does require DOM checking, but for capabilities and not browser signature. It's the right thing to do :-)

Once you know if the browser can support, you can show your video tag or pull up a lightbox or redirect as you see fit.

One really good way to tackle this problem is to use modernizer js library.Its really easy to use and quick.It can check HTML5 capabilities in the user's browser . Visit the site here : http://www.modernizr.com/

Video for Everybody's test page indicates that Firefox 3.5 can only play OGG. You might want to add a flash version if you really don't want to add OGG. VfE also does not use JavaScript, so it might be worth looking into.