Fast CU size and mode decision algorithm for 3D-HEVC intercoding

The 3D High Efficiency Video Coding (3D-HEVC) is an extension of the last 2D video coding generation (HEVC) using the Multi-view Video plus Depth map (MVD) format. In inter-coding process, the 3D-HEVC uses multiples inter prediction modes for each Coding Unit (CU) size. These prediction modes are performed to use all the possible CU sizes to select the one with the least Rate Distortion (RD) cost as the best prediction mode using Lagrange multiplier. It achieved high coding efficiency but it consumes an extremely time coding which limits 3D-HEVC from real-time applications. In this paper, a fast inter prediction mode and CU size decision algorithm is proposed to reduce the complexity of 3D-HEVC inter-coding. This algorithm is based on the homogeneity of CU using structure tensor. An experimental analysis is first performed to study the correlation of the CU complexity with depth levels and prediction modes, then the structure tensor of each CU is extracted to characterize the CU homogeneity, which has strong relationship with coding levels and inter prediction modes. Finally, a fast algorithm is adopted to accomplish an early termination of CU split and skip unnecessary prediction modes. The experimental results demonstrate that the proposed fast algorithm can provide a considerable encoding time-saving with negligible rate-distortion performance loss compared to the original 3D-HEVC encoder.