You can't just claim that a .mp4 file is video/ogg. That's a lie.
That said, you're also claiming that it's video/mp4, so as long as that is factually true (just because the file is .mp4 doesn't mean it is MPEG-4) then it should work is just about all browsers.
All major browsers have an error console you can look at for hints as to why something is not working...