Fast single depth intra mode decision for depth map coding in 3D-HEVC
In 3D-HEVC, single depth intra mode has been applied and has been integrated into depth intra skip mode for efficient depth map coding. With single depth intra mode, one 2N×2N prediction unit (PU) is predicted without high computational prediction process. In this paper, we propose a fast single depth intra mode decision method to address the problem of high computational complexity burden in depth intra mode decision of 3D-HEVC. To remove unnecessary computational complexity at the encoder, we early decide single depth intra mode for pruning quadtree in 3D-HEVC. This paper characterizes the statistics of smooth depth map signals for depth intra modes and analyzes distortion metrics of view synthesis optimization functionality as a decision criterion. With this proposed criterion, a single depth intra mode for intra coding has been detected and hierarchical CU/PU selection for intra coding can be stopped in 3D-HEVC. As a consequence, it utilizes the correlation between hierarchical block-based video coding and coding unit (CU)/PU mode decision for depth map coding so that a large number of recursive rate-distortion cost calculations can be skipped. We demonstrate the effectiveness of our approach experimentally. The simulation results show that the proposed scheme can achieve approximately 25.6% encoding time saving with 0.07% video PSNR/total bitrate gain and 0.18% synthesized view PSNR/total bitrate loss under all intra configuration.