Hybrid Fast Intra Mode Decision and Early Termination of Prediction Unit (PU) Splitting for HEVC

Abstract

SATD (Sum of Absolute Transformed Difference) based cost function is adopted to reduce the complexity of HEVC (High Efficiency video coding) codec by selecting up to 8 intra modes for RDO (Rate Distortion Optimization) process. However, transform of all 35 modes, and RDO of 8 modes is bottleneck in intra mode complexity reduction. In this paper, a hybrid approach for reducing intra coding complexity is proposed. Firstly, DC mode is declared as the optimal mode whenever the variance of available reference pixels is zero. Secondly, working of RMD (Rough Mode Decision) is optimized by evaluating transform of fewer modes than 35 modes. Thirdly, modes list to RDO is refined using neigh boring modes correlation concept. Finally, an early PU split termination technique is proposed which compares RD of available sub-PUs to the RD of 2N×2N PU. Experimental results demonstrate that average time saving of the proposed approach is 40%, while the BD-Bit Rate increment is only 0:37%.