Of the fakes: Some NGO:s are vetting film material to tag specific ones as credible evidence of e.g. states behaving badly. They compare time of day to known weather patterns, cross reference previous film to see if something has been reused etc.
That basically sounds like the dream world of DRM people, though.
(Canon had a "trusted" model as such. It was broken, IIRC by elcomsoft, shortly after release).
The important point is " making it harder " - but how hard is hard enough depends on the party in question, and for many important ones, the simple answer is "not hard enough".
Maybe also cross-linking chains of trust with nearby devices. So devices corroborate each other.
Look at the TLS x509 PKI, its a total complete mess.
This is not a workable solution.
Works for a fair few countries.
And who tags the NGOs? Of which a great many are sponsored from other states...