Does IE9 use codec from Media Player?

I offer some video using videotag and videojs to support muliple browsers. It works very well in most browsers but IE9. Some IE9 users can't play the video and they doesn't have the Media Player in common. After installed Media Player, it works.

So, does IE9开发者_Go百科 use codec from Media Player, and it doesn't embed? If it does, it'd be a big accessibility problem, I think.

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Which video formats are you serving up? IE9 supports MP4 natively, and WebM if the correct plugin is installed.