I think you'd be struggling to backup a 750 Mb movie to 700MB or less using any normal file compression technique in any case. Video doesn't & never has compressed very much or very safely using techniques such as zip/sit/other similar format. Video, to my experience & training is the most easily corrupted transporting & of course takes the most strain of the processor & ram when processing (let's leave 3d aside for a moment.) Personally I'v persistently had problems transporting video (particularly if it was on a cd as a back up.)

Prless: I'm sure it can be decent. But many factors can play a part. And how many out there really have the knowledge/finetuning exp to make it a reasonable output (not to mention the apps they use good/crappy.)