Patent ID: 6876702

Claim:
A method for determining motion vectors for encoding picture data in a sequence of pictures wherein data representing a picture in the sequence is arranged in a plurality of adjacent data blocks; the method comprising the steps of: (a) encoding a first picture in the sequence with motion vectors for the data blocks in the first picture; (b) generating respective local motion vectors for groups of adjacent data blocks in the first picture, wherein a local motion vector for each group of data blocks is generated according to the individual motion vectors of the data blocks in the group; (c) selecting a data block of an object picture to be coded; (d) determining a window of search data from a reference picture on the basis of the corresponding position of the selected data block and the local motion vector which corresponds to the selected data block; (e) comparing the selected data block with the search data from the reference picture in order to determine a motion vector for the selected data block; and repeating the steps (c), (d) and (e) for each data block in a group of adjacent data blocks in the object picture, wherein the step (e) involves storing the window of search data in a cache memory, and wherein each successive iteration of the step (e) after an initial operation requires only a fraction of the search data window to be cached.