Fast Intra Prediction Algorithm with Enhanced Sampling Decision for H.265/HEVC

Sio Kei Im, Mohammad Mahdi Ghandi, Ka-Hou Chan

Abstract: H.265/HEVC is the latest video coding standard, which offers superior compression performance against H.264/AVC at the cost of greater complexity in its encoding process. In the intra coding of HEVC, a Coding Unit (CU) is recursively divided into a quad-tree-based structure from the Largest Coding Unit (LCU). At each level, up to 35 potential intra modes should be checked. However, examining all these modes is very time-consuming. In this paper, an intra mode decision algorithm is proposed that reduces the required computations while having negligible effect on Rate-Distortion (RD) performance. A rough mode decision method based on image component sampling is proposed to reduce the number of candidate modes for rough mode decision and RD optimization. To balance the quality and performance, the decision to reduce the full search is made with a threshold that is dynamically updated based on the Quantization Parameter (QP) and CU size of each recursive step. Experiments show that our a