Fast motion estimation algorithm using spatial correlation of motion field and hierarchical search

A new block matching algorithm specially proper for a large search area, is proposed. The algorithm uses spatial correlation of motion field and hierarchical search. Motion vectors of casually neighboring blocks can be credible motion vector candidates of the current block, if the motion field has high spatial correlation. However, they are not helpful for searching complex or random motion. Our hierarchical scheme consists of the higher level search that uses the motion vectors of neighboring blocks for continuous motion and evenly distributed motion vector candidates for random or complex motion, and the lower level search for the final motion vector refinement. Compared with the conventional hierarchical BMA, the scheme reduces the local minimum phenomenon. It also alleviates the error propagation due to the use of spatial correlation when the complex motion is involved. Simulation results show that the proposed algorithm drastically reduces the computational complexity to about 3.6% of that of FS-BMA, with the minor PSNR degradation of 0.29 dB even in the worst case.