As I hinted at aboveif each frame is completely different from the previous (in other words, if there aren't any blocks of pixels that stay exactly the same from one frame to the next) that kind of file size is expected. Especially, if you don't have largish blocks of one solid colour (and most video doesn't have any blocks of solid colour to speak of).
(
but the hedgehog can never be buggered at all foreskin of the apocalypse,
Sat 1 Mar 2008, 23:38,
archived)