I'm trying to use <video> tag feature. I've encoded my file with ffmpeg:

ffmpeg -i 1.vob -f ogg -vcodec libtheora -b 800k -g 300 -acodec libvorbis -ab 128k out.ogv

I've placed this text in index.html:
<video src="out.ogv" controls></video>

I've loaded this files to nginx document root and opened index.html in Firefox 3.5. I see the first frame, see controls, but can't play video. This video plays good even from my server.

How should I encode video to view it in browser?

UPD:

If I start playing video from the middle, everything works fine.