I would imagine it using a Shazam-like algorithm, only for downsampled video and not just the audio. A decade ago there was some hobby implementations of these

I would imagine it using a Shazam-like algorithm, only for downsampled video and not just the audio. A decade ago there was some hobby implementations of these algorithms that got cease and desist letters form Shazam and that was all over HN. https://m.youtube.com/watch?v=8Dj0rekeM7g https://m.youtube.com/watch?v=8Dj0rekeM7g