基于方向梯度的H.264帧内预测模式选择算法  

Intra-Prediction Mode Decision Algorithm Based on Orientation Gradient for H.264

作　　者：宋云[1,2] 沈燕飞[2] 龙际珍[1] 朱珍民[2] 

机构地区：[1]长沙理工大学计算机与通信工程学院,长沙410014 [2]中国科学院计算技术研究所,北京100190

出　　处：《计算机学报》2013年第8期1757-1764,共8页Chinese Journal of Computers

基　　金：国家自然科学基金(61001123;60973113);湖南省科技计划项目(2012FJ4129;2012GK3056;2013FJ4033);长沙市科技计划重点项目(K1104022-11;K1207027-11)资助~~

摘　　要：率失真优化(RDO)技术的应用大幅提高了H.264的编码性能,但全搜索方式下,每一宏块所有模式都要进行R-D代价计算,复杂度非常大.文中利用参考像素与当前块之间的方向梯度检测预测方向上的纹理方向与边缘强度,预先筛除部分方向梯度较大的预测模式,形成一种基于方向梯度的快速帧内预测模式选择算法,并利用预测模式的空间相关性采用最有可能模式替换直流模式作为缺省候选模式,改进了基本算法.对10个标准序列进行测试,两个算法应用在亮度分量帧内预测模式选择中均比JM18.0全搜索方式减少了50%以上的编码时间,且编码性能损失很小,保持峰值信噪比与JM全搜索方式相同时,基本算法码率平均上升2.361%,改进算法码率平均上升1.477%.The rate distortion optimization（RDO） technique employed in H.264 improves coding performance significantly,but a very high computational load is introduced because under full search fashion every macroblock needs calculate R-D costs for all the prediction modes.In this paper,a fast intra-prediction mode decision algorithm based on orientation gradient is proposed to reduce R-D cost calculation.In the proposed algorithm,the gradients between the reference pixels and the current block pixels are calculated in all the prediction directions to detect texture direction and edge strength,and then the prediction modes with larger gradients are prepruned in the prediction process to accelerate encoding.And further,utilizing the spatial correlation of the prediction mode an improved algorithm is presented which adopts most probable mode（MPM） as the default candidate mode instead of direct current（DC） mode.Experimental results for 10 standard sequences demonstrate that compared with JM18.0 full search fashion both the baseline and the improved algorithms employed in luma component intra prediction save more than 50% of the encoding time with a negligible coding performance loss.Keeping the same peak signal-to-noise（PSNR） as JM full search,the baseline algorithm has a bit rate increment of 2.361% and the improved algorithm has a bit rate increment of 1.47% averagely.

关 键 词：视频编码 H 264 率失真优化 模式选择 

分 类 号：TP391[自动化与计算机技术—计算机应用技术]