为降低高效视频编码(HEVC)中帧内预测编码复杂度和编码耗时,提出一种基于预测单元(PUs)尺寸的HEVC帧内预测模式快速选择的改进算法。对最大尺寸PUs利用统计概率分层构建进入粗选择模式(RMD)过程的模式列表,对其他尺寸PUs分别采用两种不同方式提取纹理方向构建进入RMD过程的模式列表,其中对32×32、16×16尺寸PUs采用像素梯度提取纹理方向,对8×8、4×4采用像素值偏差提取纹理方向,从而减少进入RMD过程模式数量,有效降低编码时间。实验结果表明,本算法所用编码时间比测试模型HM16.9减少32.2%,而码率仅仅增加了0.86%。与现有优秀算法相比,本文算法进一步降低编码耗时,保证了编码质量。

To reduce the computational complexity and time consumption of intraframe prediction in high-efficiency video coding (HEVC), an improved algorithm for intraframe prediction mode fast selecting in HEVC based on the size of the prediction units (PUs) is proposed. For the maximum size of PUs, the statistical probability is used to hierarchically set the candidate modes into the rough mode decision (RMD) process. For other PUs, candidate modes are set by extracting the texture direction in two different ways into the RMD process. We use the pixel gradient for the 32×32 and 16×16 PUs and use pixel value deviation for the 8×8 and 4×4 PUs to extract the texture direction; therefore, fewer modes are selected to calculate and reduce the time taken by the RMD process. Experimental results show that the proposed algorithm reduces the encoding time by approximately 32.2% on average with only a 0.86% increase in code rate in comparison with HM16.9. In compared with the existing algorithms, the proposed algorithm further reduces the coding time and produces better coding quality.