Fast intra mode decision for HEVC video encoder

Today, H.264/AVC coding standards is widely used for efficient coding of video signals. But to cope with resolutions higher than high definition (HD) more efficient coding is needed. A successor to the H.264/AVC codec is now developed by JCT-VC standard called High Efficiency Video Coding (HEVC). To improve the coding efficiency of intra frame, up to 35 intra prediction modes are defined in HEVC. A list of candidates for Rate Distortion Optimization (RDO) is formed by considering all the 35 intra prediction modes using a process called Rough Mode Decision (RMD). We note that each intra-mode processing in RMD is quite compute-intensive. To alleviate this computation load, this paper proposes a new method to reduce the number of intra-prediction modes in RMD process. This method plans to use direction information of the co-located neighboring block of previous frame along with neighboring blocks of current frame to speed up intra mode decision. In this proposed method, a candidate list is created which includes only 17 modes instead of 35 modes used in reference software. Experimental results show that this method selects 35%, 23% and 36% intra mode from candidate list for main profile Class A, B and E cases on an average as compared to the default encoding scheme in HM 6.0 with almost the same coding efficiency. This reduces complexity of rough mode decision algorithm.