you don’t even need to cryptographically verify in that case because you already have a trusted authority: the whitehouse… of the video is on the whitehouse website, it’s trusted with no cryptography needed
the technical solutions only come into play when you’re trying to modify the video and still accurately show that it’s sourced from something verifiable
heck you could even have a standard where if a video adds a signature to itself, editing software will add the signature of the original, a canonical immutable link to the file, and timestamps for any cuts to the video… that way you (and by you i mean anyone; likely hidden from the user) can load up a video and be able to link to the canonical version to verify
in this case, verification using ML would actually be much easier because you (servers) just download the canonical video, cut it as per the metadata, and compare what’s there to what’s in the current video
not really… signing is only possible on exact copies (like byte exact; not even “the same image” but the same image, formatted the same, without being resized, etc)… there are things called perceptual hashes, and ways of checking if images are similar, but cryptography wouldn’t really help there