A fast CU partition and mode decision algorithm for HEVC intra coding

The latest video coding standard H.265/HEVC is a milestone because it can achieve up to 50 % coding performance improvement compared to the widely used H.264/AVC, owing to the newly introduced coding tools. However, these new techniques also introduce dramatic computational complexity increase. In order to release the computational burden while maintaining the coding efficiency, a two-part fast intra coding algorithm is proposed in this paper. First a CTU depth range prediction and two Bayesian decision rules are applied to accelerate the CU partition process. The depth search range of the current CTU is restricted by the neighboring CTUs on account of the spatial correlation. And one early split and one early termination strategies is presented based on the minimum Bayesian decision rule. Next, a three-step fast intra mode decision algorithm is performed to speed up the intra coding, both the depth information and the orientation information of the current CU are used to skip some unnecessary intra mode check, and the order of Most Probable Modes (MPM) is adjusted to further remove redundant calculation. As demonstrated in the experimental results, our proposed algorithm can reduce 52.9% encoding time on average with the cost of an negligible coding efficiency loss under the All-Intra configuration.