基于HEVC的帧内预测模式决策和编码单元划分快速算法

Fast intra mode prediction decision and coding unit partition algorithm based on high efficiency video coding

针对高效视频编码(HEVC)帧内预测过程中的高计算复杂度问题,提出一种基于纹理特征的预测模式选择和编码单元划分的快速帧内预测算法。利用每一深度层纹理方向强度判断编码单元是否需要进行分割,并且减少候选模式数量。首先,在每一深度层编码单元上结合像素方差,以像素点为单位计算相应的纹理方向强度,确定其纹理复杂度并结合阈值策略预测最终划分深度;其次,比较垂直和水平方向强度关系及统计预测候选模式概率分布,以减少预测模式数量,确定最优候选模式子集,进一步降低编码复杂度。所提算法与平台HM15.0相比,编码时间平均节省51.997%,BDPSNR(Bjontegaard Delta Peak Signal-to-Noise Rate)仅降低0.059 d B,BDBR(Bjontegaard Delta Bit Rate)仅上升了1.018%。实验数据表明,在保证信噪比和比特率基本不变的同时,所提算法能有效降低编码复杂度,利于HEVC的实时视频应用。

Due to the high complexity of intra encoding in High Efficiency Video Coding(HEVC),an efficient intra encoding algorithm combining coding unit segmentation and intra mode selection based on texture feature was proposed.The strength of dominant direction of each depth layer was used to decide whether the Coding Unit(CU)need segmentation,and to reduce the number of intra modes.Firstly,the variance of pixels was used in the coding unit,and the strength of dominant direction based on pixel units to was calculated determine its texture direction complexity,and the final depth was derived by means of the strategy of threshold.Secondly,the relation of vertical complexity and horizontal complexity and the probability of selected intra model were used to choose a subset of prediction modes,and the encoding complexity was further reduced.Compared to HM15.0,the proposed algorithm saves 51.997%encoding time on average,while the Bjontegaard Delta Peak Signal-to-Noise Rate(BDPSNR)only decreases by 0.059 dB and the Bjontegaard Delta Bit Rate(BDBR)increases by 1.018%.The experimental results show that the method can reduce the encoding complexity in the premise of negligible RD performance loss,which is beneficial to real-time video applications of HEVC standard.