As I understand it, the brilliant idea is that the small variantions in brightness of the pixels look just like standard noise. Distinguishing the actual noise from the algorithm is not possible, but it is still possible to verify that the 'noise' has the correct pattern.
Correct pattern for the correct time span matching random fluctuations in the electrical grid.
I think that will be handled by the AC to DC conversion in most systems.
Nope. Mains hum is picked up by microphones as well as light intensity:
https://en.wikipedia.org/wiki/Electrical_network_frequency_a...