Maybe you have to encode the video specifically for the device eg:
<video id="movie" width="320" height="240" autobuffer controls>
<source src="pr6.ogv" type='video/ogg; codecs="theora, vorbis"'>
<source src="pr6.mp4" type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'>
<source src="pr6.mp4" type='video/mp4; codecs="some droid video codec, some droid audio codec"'>
</video>
There are some examples of encoding configurations that worked on here: