高效率视频编码帧内预测编码单元划分快速算法

高效率视频编码(HEVC)采用基于编码单元(CU)的四叉树块分区结构，能灵活地适应各种图像的纹理特征，显著提高编码效率，但编码复杂度大大增加，该文提出一种缩小深度范围且提前终止CU划分的快速CU划分算法。首先，在学习帧中，基于Sobel边缘检测算子计算一帧中各深度边缘点阈值，缩小后面若干帧中CU遍历的深度范围；同时，统计该帧中各CU划分为各深度的率失真(RD)代价，计算各深度的RD代价阈值。然后，在后续视频帧中，利用RD代价阈值在缩小的深度范围内提前终止CU划分。为了符合视频内容的变化特性，统计参数是周期性更新的。经测试，在平均比特率增加仅1.2%时，算法时间平均减少约59%，有效提高了编码效率。

Fast Coding Unit Splitting Algorithm for High Efficiency Video Coding Intra Prediction

High Efficiency Video Coding (HEVC) adopts a quadtree-based Coding Unit (CU) block partitioning structure which is flexible to adapt to various texture characteristics of images and can improve the coding efficiency significantly; however, it also introduces a great computation complexity. This paper proposes a fast CU splitting algorithm which can narrow CU depth range and early terminate the CU splitting. Firstly, in learning frame, based on the Sobel edge detection operator, this study obtains edge point threshold at each CU depth level to narrow the CU traversal depth range in the next several frames. Meanwhile, this paper introduces the statistical of Rate-Distortion (RD) cost of CU in the frame and calculates RD threshold of each depth level. Then, in the subsequent video frames, RD threshold is utilized to terminate early the CU splitting in the narrow depth range. The statistical parameters are periodically updated to cope with varying video content characteristics. The experimental results show that the proposed algorithm is able to save 59% encoding time on average with only 1.2% increasing on bit-rate which can observably improve the coding efficiency.