Datamoshing

Datamoshing is the practice of using intentionally corrupted digital video as a form of art.

Digital video compression (such as MPEG-4 part 2, h.264, VP8, etc) works by recording the first frame (known as the keyframe) as a complete image, and recording the subsequent frames as only the changes from this first frame. This is done because recording only the changes makes the video easier to compress. By replacing the first frame of a compressed video with another picture, these same changes will be applied to the new image, creating very unusual-looking psychedelic effects.

Usually lossy video codecs are used, as lossless codecs do not usually record enough motion information to achieve the effect. Different codecs produce different effects. Older codecs such as MPEG-1 or MPEG-2 tend to produce very blocky distortion, whereas newer codecs such as h.264 tend to produce more fluid distortion. This can be attributed to the deblocking filter present in newer codecs. Google’s VP8 codec tends to produce very chaotic distortion. Wavelet-based codecs such as Dirac also produce very different distortions. The technique does not work at all with codecs that record every single frame as a complete image, such as MJPEG. Most codecs also insert a new keyframe (complete image) every 12 to 250 frames, depending on the codec, so this keyframe insertion must be disabled or increased to a high number to datamosh properly.

The effect is becoming popular in music videos, and has been used in videos from mainstream artists such as Kanye West. In West’s video, the audio also has an effect applied, which goes along well with the distorted video. Parts of the video also have an analog videotape-style distortion, combining both analog and digital distortion.