Abstract: In order to reduce the encoding complexity of the emerging High Efficiency Video Coding (HEVC), a fast hierarchical algorithm based on texture property and spatial correlation for intra coding was proposed. Firstly, Largest Coding Unit (LCU) level fast algorithm was adopted. The prediction depth of current LCU was derived by weighted prediction using the depth level of neighboring LCUs; the texture complexity of current LCU was determined by means of standard deviation and the strategy of adaptive threshold. Therefore, the Most Probable Depth Range (MPDR) of current LCU could be predicted by combining the prediction depth with the texture complexity of current LCU. Secondly, using Coding Unit (CU) level Depth Decision Fast Algorithm (CUDD-FA), combining the strategy of early decision of CU depth level based on edge-map with early termination of CU depth based on Rate Distortion (RD) cost correlation, the depth level of CU was determined before coding, and the complexity of intra coding process was further reduced. The experimental results show that, compared with the original HEVC encoding scheme, the proposed method reduces encoding time by an average of 41.81%, while the BD-rate (Bjøntegaard Delta bit rate) only increases by 0.74% and the BD-PSNR (Bjøntegaard Delta Peak Signal-to-Noise Rate) only decreases by 0.038 dB; compared with the representative literature algorithms, the proposed algorithm achieves better RD performance with saving more encoding time. The proposed method can significantly reduce the complexity of intra coding process in the premise of negligible RD performance loss, especially for video sequences with high resolution, which is beneficial to the real-time video applications of HEVC standard.

Key words: High Efficiency Video Coding (HEVC), fast intra coding, texture property, spatial correlation, early termination

摘要： 为了降低高效视频编码(HEVC)标准的编码复杂度,提出一种基于纹理特性与空域相关性的帧内分级快速算法。首先,采用最大编码单元(LCU)级的快速算法,通过利用相邻LCU的编码深度值加权预测得到当前LCU的预测深度,并利用块标准差和自适应阈值策略确定当前LCU的纹理复杂度,将当前LCU的预测深度和纹理复杂度相结合来预测当前LCU的最有可能深度范围(MPDR);其次,采用编码单元(CU)级的深度判决快速算法(CUDD-FA),将基于边缘图的CU深度预判策略和基于率失真(RD)代价相关性的CU提前中止策略相结合,实现了CU级深度的提前确定,进一步降低了帧内编码复杂度。与原始HEVC算法相比,所提算法在全I帧编码模式下编码时间平均减少41.81%,BD-rate(Bjøntegaard Delta bit rate)仅上升0.74%,BDPSNR(Bjøntegaard Delta Peak Signal-to-Noise Rate)仅降低0.038 dB;与代表性文献算法相比,所提算法在编码时间节省更多的情况下率失真性能更好。实验结果表明,在率失真性能损失可以忽略不计的前提下,所提算法能有效降低HEVC帧内编码复杂度,特别是高分辨率视频序列,有利于HEVC的实时视频应用。

关键词: 高效视频编码, 帧内快速编码, 纹理特性, 空域相关性, 提前中止