I guess it would be a watermark style change through all the video frames which affects the hashes - e.g. brightness or contrast or sharpness or some combinatio

I guess it would be a watermark style change through all the video frames which affects the hashes - e.g. brightness or contrast or sharpness or some combination of that kind of thing - then seed that on torrent sites, and advertisers get to see which TVs watched the torrented film vs the official film.