Adaptive search range for HEVC motion estimation based on depth information

High Efficiency Video Coding achieves twofold coding efficiency improvement compared with its predecessor H.264/MPEG-4 Advanced Video Coding. However, it suffers from high computational complexity due to its quad-tree structure in motion estimation (ME). This paper exposes the use of depth maps in the multiview video plus depth format for relieving the computational burden. The depth map provides an intimation of the objects' distance from the projected screen in a 3D scene, which is explored in adaptive search range determination in this paper. The proposed algorithm exploits the high temporal correlation between the depth map and the motion in texture. By utilizing this correlation, a depth/motion relationship map is built for a mapping process. For each block, this forms a tailor-made search range with a motion-aware asymmetric shape to skip unnecessary search points in ME. The obtained search range can be further adjusted by taking the influence of 3D-to-2D projection into consideration. Simulation results reveal that, compared to the full search approach, the proposed algorithm can reduce the complexity by 93% on average, whereas the coding efficiency can be maintained. Besides, the proposed search range determination can work well with other fast search ME algorithms in the literature.