Fundamentally we as a species have lost the use of face and voice in a video to establish authenticity.
A person can spoof an email, and we have cryptographic signatures as a means of authentication.
So if I record myself saying something I could sign the video I guess (implementation TBD lol).
But what if someone else (news agency say) takes a video of someone else, how do we authenticate that?
If it's a news agency they could sign it. Great.
But then we have the problem of incentives, too. Does the benefit of a fake outweigh the detrimental effects for said news agency?
The most damage would be to the person being videoed (reputation, loss of election, whatever). There would be less damage to the media company ("oops so sorry please stay subscribed"). You could add fines but corporate oversight is weak. And the benefit of releasing a fake would be clicks and money so a news company would be a lot more likely to pass along a fake as real.
So I guess I have no idea what we do. At the moment we are fucked. Yay.