Ah ok I didn’t know the EU thing. For the algorithm it’s a cat and mouse game. You could try to detect it by hash signatures of the segments or some kind of image detection but they could in turn add bytes to change the signature or other attributes. Could require a lot of effort on the blocking site to have the indicators up to date.
As I know they transcode every uploaded video to their preferred format. They could use the same infrastructure for the ads. But maybe it’s really too expensive.