Video Artifacts/Pixellation

Breaking up of the picture into small flickering colored squares.

Pixellation is most often an artifact of insufficient playback horsepower, or conversely, excessive bitrate. In either case it is due to the playback mechanism not being able to keep up with the data rate.

It is sometimes caused by a dirty lens or faulty transport mechanism in a dvd player.

Some pornographic video material uses an intentional pixellation effect to mask "the naughty bits".