Fast Intra size decision and mode decision algorithm for HEVC intra coding

Abstract

The latest High Efficiency Video Coding (HEVC) standard could achieve much higher coding efficiency than the current mainstream video coding standards (H.264/AVC). Compared with H.264/AVC, H.265 saves 50% cost than H.264/AVC at the same quality. But compression ratio gets improved with at least 2-4 times increase in computational complexity. HEVC provides a quad-tree based coding unit (CU) block partitioning structure. The predication mode of CU has been extended from 8 to 35. To alleviate the encoder computational complexity, we proposed an algorithm based on complexity of CU and cart decision tree to determine whether the current CU should be divided into quad-tree. In the mode decision process, we reduce the number of candidate modes involved in the rough mode decision(RMD) and the rate distortion optimization (RDO) process. The experiment results demonstrate that the proposed algorithm could significantly reduce compression time with little loss.