High efficiency video coding (HEVC) is the newest video coding standard, which employs some advanced coding techniques as compared to the previous standard H.264. The flexible quad-tree partitioning of coding tree unit (CTU) and various candidate modes of prediction unit (PU) significantly promote the video compression efficiency; however, these techniques lead to a great amount of computational loads. In this paper, a fast mode decision algorithm for HEVC intra coding is proposed based on texture partition and direction. It consists of two sub-algorithms: the CTU depth range prediction (CDRP) and the intra-prediction mode selection (IPMS). The CDRP reduces the recursive partition number of coding unit (CU) based on the correlation between the CTU texture partition and the optimum CU partition, and it first calculates the texture partition flags of different-size CUs from bottom to top. Then, it employs these partition flags to predict the depth range of the current CTU and decide whether to terminate the CU partition in advance. In order to reduce the number of candidate PU modes for the Hadamard optimization, the IPMS first uses the three-step selection of the candidate modes. The first step selects the candidate modes based on the correlation between the texture directions and the optimum PU modes. The second step selects the candidate modes by using the best modes among the selected modes in the first step. The third step selects the candidate modes by using the spatial correlation of the optimum modes between the current PU and its adjacent PUs. Then, in order to reduce the number of candidate modes for the rate-distortion optimization, the IPMS utilizes the numerical relationship of the sorted Hadamard costs of above selected modes, the optimum modes of adjacent PUs and the statistical characteristics of the small-size PUs. Compared to the original algorithm in HEVC test model, the proposed overall algorithm can reduce 60% encoding time on average with only a 1.45% increase in Bjontegaard delta bit rate under the all-intra configuration. Compared to the most of state-of-the-art algorithms, the proposed overall algorithm has better computational performances and similar rate-distortion performances.

中文翻译：

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基于纹理划分和方向的HEVC帧内编码快速模式决策算法

高效视频编码（HEVC）是最新的视频编码标准，与以前的标准H.264相比，它采用了一些先进的编码技术。编码树单元（CTU）的灵活四叉树划分和预测单元（PU）的各种候选模式大大提高了视频压缩效率；但是，这些技术导致大量的计算负荷。本文提出了一种基于纹理划分和方向的HEVC帧内编码快速模式决策算法。它由两个子算法组成：CTU深度范围预测（CDRP）和帧内预测模式选择（IPMS）。CDRP根据CTU纹理分区和最佳CU分区之间的相关性减少编码单元（CU）的递归分区数，首先计算从底部到顶部的不同大小CU的纹理分区标志。然后，它使用这些分区标志来预测当前CTU的深度范围，并决定是否提前终止CU分区。为了减少用于Hadamard优化的候选PU模式的数量，IPMS首先使用候选模式的三步选择。第一步，根据纹理方向和最佳PU模式之间的相关性选择候选模式。第二步通过使用第一步中所选模式中的最佳模式来选择候选模式。第三步骤通过使用当前PU与其相邻PU之间的最佳模式的空间相关性来选择候选模式。然后，为了减少用于速率失真优化的候选模式的数量，IPMS利用上述选定模式的已排序Hadamard成本，相邻PU的最佳模式以及小型PU的统计特性的数值关系。与HEVC测试模型中的原始算法相比，所提出的整体算法在全帧内配置下平均可减少60％的编码时间，而Bjontegaard增量比特率仅增加1.45％。与大多数最新算法相比，所提出的整体算法具有更好的计算性能和相似的速率失真性能。与HEVC测试模型中的原始算法相比，所提出的整体算法在全帧内配置下平均可减少60％的编码时间，而Bjontegaard增量比特率仅增加1.45％。与大多数最新算法相比，所提出的整体算法具有更好的计算性能和相似的速率失真性能。与HEVC测试模型中的原始算法相比，所提出的整体算法在全帧内配置下平均可减少60％的编码时间，而Bjontegaard增量比特率仅增加1.45％。与大多数最新算法相比，所提出的整体算法具有更好的计算性能和相似的速率失真性能。