Some kind of perceptual hashing and whatever additional magic YouTube uses to detect copyrighted stuff? Once a video is flagged, it can be added to the perceptu

Some kind of perceptual hashing and whatever additional magic YouTube uses to detect copyrighted stuff? Once a video is flagged, it can be added to the perceptual database in a fraction of a second and all future uploads checked against it, YouTube seems to have gotten good at it.