Reminds me of the 'mains hum' technique that was used to identify videos. Can also be done with light. https://www.youtube.com/watch?v=e0elNU0iOMY https://www.

Reminds me of the 'mains hum' technique that was used to identify videos. Can also be done with light. https://www.youtube.com/watch?v=e0elNU0iOMY https://www.youtube.com/watch?v=e0elNU0iOMY https://en.wikipedia.org/wiki/Electrical_network_frequency_analysis https://en.wikipedia.org/wiki/Electrical_network_frequency_a...