Both videos (up to 300 s each) are sampled at sample_fps from their start, each ...
https://ton.halowerk.com/v1/video-dup-detectOverview
Both videos (up to 300 s each) are sampled at sample_fps from their start, each sample is reduced to 64×64 grey and hashed with a 64-bit DCT perceptual hash (pHash method; aspect ratio ignored, so rescaling does not matter). Flat samples (standard deviation below 4 grey levels on the 32×32 image) carry no information and are skipped. Every time offset between the two sequences is tried; at each offset a pair of samples matches when their hashes differ in at most max_hamming bits.