I was thinking more along the lines of hardware manufacturers implementing a secure enclave style of signing files as they're recorded. The sig could be tagged with location/date if available, but at least the video would be verifiable. The web of trust would have to exist for reprocessors and media outlets who like to edit footage.
Nope, it'll just give well-executed fakes a veneer of legitimacy. A state-level actor will have easy access to the signing keys. Non-state-level actors could potentially extract them from a device or bribe an engineer at a third-tier Chinese OEM. A reasonably competent hardware hacker could desolder the CCD from a signed device and feed whatever video signal they like into it.
