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基于HEVC的帧内模式决策和CU划分快速算法

郭磊,王晓东,徐博文,王健   

  1. 宁波大学
  • 收稿日期:2017-09-22 修回日期:2017-11-27 发布日期:2017-11-27
  • 通讯作者: 王晓东

Fast prediction mode decision and CU size algorithm based on HEVC

  • Received:2017-09-22 Revised:2017-11-27 Online:2017-11-27

摘要: 针对高效视频编码(High Efficiency Video Coding,HEVC) 帧内预测过程中的高计算复杂度问题,提出了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处理,并且预测减少候选模式。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CU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减少帧内预测模式数量,确定最优的候选模式子集,进一步减少编码复杂度。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0.059dB,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。

关键词: 高效视频编码, 帧内预测, 纹理方向, 编码尺寸, 模式选择

Abstract: Due to the high intra encoding complexity of High Efficiency Video Coding (HEVC), an efficient coding unit partitioning technique and intra mode decision method based on texture features was proposed. The strength of dominant direction of each depth was used to decide whether the coding unit need segmentation, and to reduce the number of intra mode. Firstly, the variance of pixels was used in the coging unit, and using the strength of dominant direction based on pixel units to determine its texture complexity, 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 was used to chose a subset of prediction modes, and the encoding complexity was further reduced. In HM15.0, the proposed algorithm is able to save 51.997% encoding time on average, while the Bjontegaard Delta Peak Signal-to-Noise Rate(BDPSNR) only decreases by 0.059dB 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 the real-time video applications of HEVC standard.

Key words: HEVC, intra prediction , texture direction, coding unit size, mode decision

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