HTML5 Video is just a convention to play a certain video formats with a new element for which browsers will implement an own player. HTML5 won’t provide players or something like that.
You have to look for the codecs and contained supported by most browsers, which, if I remember well, are mostly Theora for Video and Vorbis for audio, in an OGG container.
Then I remember that Webkit browsers will support Matroska (MKV) containers using V8 as video codec and Vorbis for audio.
My recommendation: provide an OGG file with Theora and Vorbis as video and audio codecs respectively. Inside provide a fallback using an MKV file with V8 and Vorbis and then, if you can, inside an MPG video file using Mpeg2 and MP2 (couldn’t think on something better) as video and audio codecs, fallback. Then as the last fallback, a Flash player playing a FLV video file.
<video src="thevideo.ogg">
<video src="firstFallback.mkv">
<object type="video/mpeg" src="secondFallback.mpeg">
<object
type="application/x-shockwave-flash"
src="player.swf?etc...">
<p>Download <a href="videourl">the video etc...</a><br />
or use a more modern browser to watch online, etc...</p>
</object>
</object>
</video>
</video>
Etc... ;-)
With this configuration, most (if not all) browsers should be able to play your video, preferring the most supported (and most modern) format. “Fallbacking” until they find a Flash Player.
For hints on what formats to support: take a look at the HTML5 Video part in Wikipedia.
Important: In your code you are refering to an absolute filesystem path, which is totally not-accesible for a web visitor. Maybe in the src you meant /video/file2.m4v.