[munk-a]

How would they technically accomplish this? Whenever a camcorder or phone or webcam was used would the hash be transmitted to the manufacturer and registered there? Would the device sign the video signature with some secret key? (similar to that big secret number you're not allowed to show)

Assuming you got it to work sanely, how would you ensure that all manufacturers properly locked down their devices?

Assuming there's a reasonable trust framework and you're able to enforce it... How would you allow legitimate video editing without allowing people to edit video to create misleading images? How would a movie cut between characters and an exploding model in a legitimate and signed manner without allowing someone to splice a politician's speech in with terrorist training videos?

There is a lot wrong with this "Tech can fix it" approach.