represents a pixel point in the current frame shifted from each of the feature points in the previous frame by each of the first set of motion vectors is determined the magnitude of a motion vector for a quasi feature point is identical to the motion vector for its corresponding feature point but the direction of the two motion vectors is opposite after determining the motion vectors for all of the quasi feature points motion vectors for non quasi feature points which are the remaining pixel points in the current frame are determined as follows as shown in fig3 a number of quasi feature points are irregularly distributed in the entire current frame a motion vector for a star marked non quasi feature point is calculated by averaging those for the quasi feature points which are placed within a circle boundary having a radius of d r d a wherein d a is the distance to the nearest quasi feature point from the star marked pixel position and d r is a predetermined expanded radius for including other quasi feature points to be used in the motion vector calculation for example if the nearest quasi feature point is 34 y 34 and the quasi feature point 34 x 34 is located within the boundary of d a d r the motion vector mv x mv y for the star marked pixel is calculated as equ1 wherein d x and d y are the respective distances of quasi feature points x and y from the star marked pixel position and mv x mv y x and mv x mv y y are the respective motion vectors.