People will claim this isn't possible, or will never work, but they often miss the fact that we don't need to sign every video. Only source videos of certain people need to be signed.
For example, Tom Hanks was used to shill some dental product (I think). He's a public figure. He, and we, would want to be able to validate that anything using his likeness is actually him.
For me, nobody cares if a video of me is me or not, so it doesn't need to have a signature.
Nobody cares if a video of you is you or not for now but this is subject to change in the near future. Perhaps advertising to your friends and acquaintances with a video of you selling or endorsing some scam product would make you care more?
For example, Tom Hanks was used to shill some dental product (I think). He's a public figure. He, and we, would want to be able to validate that anything using his likeness is actually him.
For me, nobody cares if a video of me is me or not, so it doesn't need to have a signature.