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Region-wise motion compensation technique using enhanced motion vectors

Despite the fact that the existing region-wise motion compensation techniques (RWMC) are more efficient than the conventional variable size block motion compensation technique, they still do not use the visual characteristic of a frame in terms of brightness, contrast and sharpness in order to determine the motion information of the partitioned regions in a most efficient manner. The objective of this paper is to present a quad-tree structured region-wise motion compensation technique using enhanced motion vectors. The scheme described in this paper uses the brightness information of a frame in order to reach the objective of having motion vectors with a higher accuracy. Even though using enhanced motion vectors reduces the distortion, it causes the bit rate to increase. This poses the challenge of optimizing the bit rate-distortion performance. The proposed method partitions a frame based on a fine to coarse resolution strategy through the merging and combining processes. The merging process permits 4-to-1, 3-to-1 and 2-to-1 merges. For such merges, the main idea is to minimize the distortion subject to the constraint that the bit rate should not exceed a pre-defined value. The combining process further reduces the total number of partitioned regions by combining some of the regions that have the same enhanced motion vectors. The proposed technique uses a 2-bit code for coding the quad-tree structure while two different code lengths encode the enhanced motion vectors of the partitioned regions depending on the differential brightness threshold value. The proposed method is applied to a number of video sequences and compared with the other existing methods. The test results show that the new method can significantly improve the rate-distortion performance.