New fast algorithms for the estimation of block motion vectors

Two algorithms for block motion estimation that produce performance similar to that of exhaustive search but with computation reduced by a factor of 8 or 16 are presented. The algorithms are based on motion-field and pixel subsampling. A subsampled motion field is first determined by estimating the motion vectors for a fraction of the blocks. The motion vectors for these blocks are determined by using only a fraction of the pixels at any searched location and by alternating the pixel subsampling patterns with the searched locations. The subsampled motion field is then interpolated so that a motion vector is determined for each block of pixels. The algorithms are more robust than previously proposed fast algorithms and both can easily be combined with a hierarchical search strategy. One of the algorithms is fully compatible with MPEG-I