The point was to sign AI footage so you know what’s fake. NFTs can be used as a decentralized repository of signatures. You could realistically require the companies to participate, but the idea doesn’t work because you can edit footage so it doesn’t match the signature. More robust signatures exist, but none is good enough, especially since the repo would have to be public.

Signing real footage makes even less sense. You’d have to trust everybody and their uncle’s signature.