I doubt if it's that simple: I'm sure that digital movies will use compression (mpeg, etc.). One flipped bit could scramble the whole frame. Even with lossless compression, error correction would be worth adding. It's going to be much easier to compress to mpeg in hardware than to design tape that can handle the required frame rate/resolution without compression.
I think signing photographs and movie images is a difficult problem. Why? Because one flipped bit will completely screw up the hash function. Errors on these tapes happen rarely, but most video manufacturers aren't really going to bother worrying about occasional bit errors because they're usually invisible to the eye. Why waste all that extra effort on error correction if it's not worth the trouble. So signed photographs will also need to contain all of the error correction necessary and that will make them more expensive. This isn't any real cost on a general purpose machine, but it matters in some places.
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