I've been thinking about this some recently. Is some scheme like the following remotely plausible?

- Have a piece of hardware in-frame that can show hashes that is hooked to the operating cameras.

- In each frame show the hash of the previous frame (low latency would be required, as would the transmission of the full-quality original).

- Publish the original seed and the final hash (and, since the original is broadcast, the whole chain of hashes can be verified).