MPEG-1 encoding
I-, P- and B-frames form a pattern depending on the encoder used … ours has an I-frame every 12 frames (2 per sec) but it does not have to be like this;
Encoders are not perfect and the 396 motion vectors in a frame (1 per macroblock) can sometimes be incorrect and have rogues;
MPEG-2 is the same principle except 720x576 pixels and is used for digital TV;
MPEG-4 is object based compression, based on identifying, tracking and encoding object layers which are rendered on top of each other, with huge potential for interaction;