Visual saliency is used to guide the codingtreeunit (CTU)-level bit allocation process in high-efficiency video coding (HEVC) to improve the visual quality. At first, a saliency detection algorithm is proposed. With...
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Visual saliency is used to guide the codingtreeunit (CTU)-level bit allocation process in high-efficiency video coding (HEVC) to improve the visual quality. At first, a saliency detection algorithm is proposed. With the detected saliency map, the distortion of each CTU is weighted by the corresponding saliency, so that the distortion of the salient areas (SAs) is more critical. Then, the optimal bit allocation problem constrained by the picture-level target bits and minimum weighted distortion is built. Numerical method is used to solve the bit allocation problem. Finally, bits reallocation and the rate distortion optimization parameters clipping methods are presented to tackle the bits error accumulation problem. Experiment results show that quality gaining in SAs is up to 0.8658 dB and the gaining of saliency weighted peak signal-to-noise ratio is up to 1.0318 dB. (C) 2018 SPIE and IS&T
Screen content video (SCV) is generated by computers, including texts, animation, and graphics. Unlike conventional camera-captured video, screen contents are often discontinuous, as some regions may remain static for...
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Screen content video (SCV) is generated by computers, including texts, animation, and graphics. Unlike conventional camera-captured video, screen contents are often discontinuous, as some regions may remain static for successive frames. Therefore, the traditional hierarchical quantisation parameter (QP) setting scheme for conventional video may be not efficient enough for SCV. In this study, an improved hierarchical QP setting method is proposed for screen content coding. Based on the default hierarchical QP setting in high efficiency video coding (HEVC), the proposed method adjusts QP values at the coding tree unit level according to block matching and content complexity. Smaller QP is assigned to the static region and the translational region to reduce quality refinement, and bigger QP is assigned to the complex and limited quality propagated region to save bits. Experimental results show that compared with the default QP setting method in HEVC, the proposed method reduces up to 15.7% bitrate and 6.3% bitrate on average, and decreases the encoding time by 9.2% averagely.
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