Intra prediction header bits estimation algorithm for RDO in H.265/HEVC

The amount of video information to store and transmit is continuously increasing. The new video compression standard H.265/HEVC provides the ability to halve video bitrate at the cost of higher computational expenses. The most time-demanding part of a compression system is decision making, especially when based on rate-distortion optimization (RDO). There are a lot of papers that tend to decrease the complexity of decision making by either reducing the number of coding options to compare or by reducing the complexity of RDO estimation. The aim of the latter approach is to eliminate from rate estimation the binary arithmetic coder (BAC), as it is the most computationally expensive step. Most of works focus on proper estimation of the residual data, while proper estimation of prediction information is either neglected or is still performed with BAC. In our work we elaborate the proper rate estimation of the prediction header without the use of BAC. The suggested algorithm counts the symbols to be coded with BAC and estimates the bit size of the intra prediction header based on the entropy of the symbols, obtained in the statistical experiments. The proposed algorithm provides the average bitrate overhead of 0.09% on JCT-VC test video sequences, and can be used as a part of decision making algorithm in H.265/HEVC video compression systems.