A hierarchical motion estimator for interframe coding

Describes an improved motion estimation method for low bit rate image coding. The phase correlation method is employed as a front-end motion estimator to a hierarchical block search scheme which provides accurate motion vectors with a large tracking range in noisy environments. To overcome residual motion vector errors, it is envisaged that in future extensions of the algorithm, the assumption will be made that motion vector fields within moving areas change smoothly. This can be achieved by a modified distortion measure that includes the deviation between the motion vector of the current block and the motion vectors of the previous horizontal and vertical blocks