Fast entropy-based CABAC rate estimation for mode decision in HEVC

Wei-Gang Chen, Xun Wang
2016 SpringerPlus  
High efficiency video coding (HEVC), which is the newly developed video coding standard, follows the so-called block-based hybrid coding architecture . HEVC aims at providing higher coding efficiency and making the codec better parallelization than the prior standards. The reference software HM (https://hevc.hhi.fraunhofer. de/svn/svn-HEVCSoftware) has achieved the expected performance, but at the cost of some high computational coding tools, including quadtree based coding unit (CU), large and
more » ... asymmetric prediction unit (PU), residual quadtree based transform unit (TU) Bossen et al. 2012; Kim et al. 2012; Corrêa et al. 2012; Pan et al. 2014) . Mode decision, which controls how a coding tree unit (CTU) is coded with CUs with variable block sizes and prediction modes, is an essential process in HEVC. To achieve the best performance, HEVC seeks the best coding tree configuration, the best PU division and the prediction mode, etc., by evaluating the rate-distortion (R-D) functional where a distortion term is weighted against a rate term using a "try all and select the best" strategy (Pan et al. 2014). Abstract High efficiency video coding (HEVC) seeks the best code tree configuration, the best prediction unit division and the prediction mode, by evaluating the rate-distortion functional in a recursive way and using a "try all and select the best" strategy. Further, HEVC only supports context adaptive binary arithmetic coding (CABAC), which has the disadvantage of being highly sequential and having strong data dependencies, as the entropy coder. So, the development of a fast rate estimation algorithm for CABACbased coding has a great practical significance for mode decision in HEVC. There are three elementary steps in CABAC encoding process: binarization, context modeling, and binary arithmetic coding. Typical approaches to fast CABAC rate estimation simplify or eliminate the last two steps, but leave the binarization step unchanged. To maximize the reduction of computational complexity, we propose a fast entropybased CABAC rate estimator in this paper. It eliminates not only the modeling and the coding steps, but also the binarization step. Experimental results demonstrate that the proposed estimator is able to reduce the computational complexity of the mode decision in HEVC by 9-23 % with negligible PSNR loss and BD-rate increment, and therefore exhibits applicability to practical HEVC encoder implementation.
doi:10.1186/s40064-016-2377-0 pmid:27386240 pmcid:PMC4912508 fatcat:xqzl2sxnqjcmbfmnpdb77qdxa4