MOTION ESTIMATION AND COMPENSATION IN VIDEO COMPRESSION

A method of video motion estimation is described for determining the dominant motion in a video image. The dominant motion is defined by a parametric transform, for example a similarity transform. In the preferred embodiment, selected pairs of blocks in one frame are traced by a block matching algorithm into a subsequent frame, and their change in position determined. From that information, an individual parameter estimate is determined. The process is repeated for many pairs of blocks, to create a large number of parameter estimates. These estimates are then sorted into an ordered list, the list is preferably differentiated, and the best global value for the parameter is determined from the differentiated list. One approach is to take the minimum value of the differentiated list, selected from the longest run of values which fall below a threshold value. Alternatively, the ordered list may be examined for flat areas, without explicit differentiation. The technique is particularly suited to low complexity, low bit rate multimedia applications, where reasonable fidelity is required without the computational overhead of full motion compensation.