ENCODING SYSTEM USING MOTION VECTORS TO REPRESENT FRAME-TO-FRAME CHANGES, WHEREIN A DECODER USES PREDICTIONS OF MOTION VECTORS IN DECODING

Video data is encoded to form compressed video data wherein at least some of the frames are encoded as nonkey frames with reference to content of reference frames. In encoding a nonkey frame, segments of a reference frame can be matched to the pixels of the nonkey frame and related by a calculated motion vector for each segment, wherein a motion vector represents a difference in position of the image area represented by the segment. Motion vectors are predicted and the encoding of the nonkey frame can omit coding for calculated motion vectors that are sufficiently close to their predicted values and encoding differences between calculated and predicted motion vectors. Differences in values can be considered residue and coded as part of residue data. A decoder making similar predictions can decode the compressed video data even when the compressed video data contains no information about the predictions for motion vectors.