Compression: motion compensation

• A great deal of the compression possible with motion video results from inter-frame redundancy. In particular, from frame to frame there is usually either little change or else there is some translation of blocks of pixels as a result of motion (of objects in the scene, or the camera).
• Motion compensation yields motion vectors indicating the direction and distance (in pixels, or possibly fractional pixels) of translation for each block that has moved.
• Developing motion vectors requires extensive (parallel) search involving successive frames.
• Reconstruction of the motion sequence is simpler, involving several buffers for a frame sequence, so one frame can be modified to yield the next.