Method, apparatus and system for encoding and decoding a transformed block of video samples

A method of decoding a coding unit in an image frame from a bitstream by determining a size of the coding unit from the bitstream; and dividing the image frame into a plurality of equally sized processing regions, each of the equally sized processing regions being smaller than a largest available coding unit size. The method also comprises selecting a motion vector corresponding to the coding unit from a list of candidate motion vectors, selecting the motion vector comprising (i) decoding a merge index if the coding unit is greater than or equal to a size than one of the determined processing regions, or (ii) decoding a skip flag to decode that the merge index if the coding unit is not greater than or equal to the size than one of the determined processing regions; and decoding the coding unit according to the selected motion vector for the coding unit.