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?

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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.

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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/

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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.