Hardware-based signing-while-recording, and only consider previously recorded self-verified unsigned recordings legitimate, otherwise unsigned=assumefake.

> only consider previously recorded self-verified unsigned recordings legitimate, otherwise unsigned=assumefake

Can you clarify this part, especially "self-verified unsigned"? I don't think I understand it - presumably you could generate camera-and-video-specific signatures which an edit couldn't reproduce, but it's not obvious to me how you would verify them without access to the original camera.

As far as sign-while-recording, I agree. We'll quickly end up in a world where video of ongoing events is signed as it's taken. The simplest tactic I can think of is submitting a hash of the video file to some public store, which at least authenticates when it was shot. For an event with a well-known time (a speech, public protest, etc), that should suffice to prove the footage isn't faked, and corroboration of multiple videos should prove it's not an outright fabrication (e.g. pre-rendering a whole different speech).

For time-nonspecific events like a video of a suspicious meeting, this wouldn't be enough. A hardware signature might prove that a video was real, but we'd still face a significant change in that unsourced videos floating around the web couldn't be treated as convincing. We're already getting there with photos, of course, but at the moment a clear, high-res video is pretty trustworthy without a source.