The signing happens using hardware inside the phone or camera. It implies that it came from a real device and thus was not AI created or modified. Check out https://c2pa.org/specifications/specifications/1.4/attestati... for more details

And what happens when people just film an AI video playing on a screen with this phone or camera?

I wonder if this will help solve problems created by shelter in place. It seems like it would be easy to spin up a website to stream classes to students using this.

Did you see the costs? Might as well use YouTube.