Content-based irregularly shaped macroblock partition for inter frame prediction in video coding

Although rate–distortion adaptive, variable block-size motion compensation has significantly contributed to the performance improvement in compression efficiency of H.264/AVC over the other existing video coding standards, the shape of the block for motion compensation prediction (MCP) in H.264/AVC is still limited to the regular rectangle. To further improve the accuracy of MCP, a novel content-adaptive macroblock partition method for inter frame prediction is proposed in this paper, where irregularly shaped partitions are introduced to MCP. The proposed method irregularly segments the current coding macroblock (MB) by referring to the matching reference region (MRR) in the reference frames, which is obtained relying on the inherent structural similarity of the video contents among successive frames and can be traced with the relative displacement vector between the current MB and the MRR. Consequently, the irregular partition of the current MB is content adaptive and the partition information is implicitly indicated by the MRR, without resorting to an explicit description of the shape information of the irregular segmentation. Experimental results demonstrate that the proposed method outperforms the MCP based on the regular rectangle blocks in terms of coding efficiency, by providing more precise motion estimation for macroblocks at little cost of extra side information.