Abstract: In order to increase the speed of motion vector calculation characteristic pixels from a macroblock are selected and the control sum is calculated only from those pixels while the coordinates of those pixels are calculated using all pixels values in the macroblock. In one embodiment the rows of pixels are re-odered in ascending value and serveral equidistant pixels selected. The columns of selected pixels are then re-ordered in increasing value order and several equidistant pixels selected to provide the characteristic pixels. In a second embodiment pixels are selectred in a drecreasing order of deviation from the mean value of a row. The selected pixels are arranged in columns and further selected on the basis of decreasing order of deviation from the absolute value of the column average. In a third embodiment the macroblock is divided into sub-blocks and a single characteristic selected having the maximum or minimum value for that sub-block. Selection of maximum or minimum alternates from block to block.