# 【HEVC帧间预测论文】P1.5 Fast Coding Unit Size Selection for HEVC based on Bayesian Decision Rule

Fast Coding Unit Size Selection for HEVC based on Bayesian Decision Rule

《HEVC标准介绍、HEVC帧间预测论文笔记》系列博客，目录见：http://www.cnblogs.com/DwyaneTalk/p/5711333.html

2012 Picture Coding Symposium May 7-9, 2012

W是决策分类，  分别表示划分和不划分。

1

1）式为naïve bayes的公式，依次是类条件、先验和后验（似然）概率。

2

2）表示决策代价，表示应该决策为Ws而实际是W的代价，其他类似。

3）、（4）式为最终的决策表达式。决策如下：

A、fvar ：The variance of mode Inter_2Nx2N prediction errors in current CU

B、fsatd：The sum of absolute transformed difference (SATD) between original and prediction of mode Inter_2Nx2N

C、fvsatd ：The variance of 4 SATDs (The prediction errors of mode Inter_2Nx2N is split into 4 sub-squares and calculate SATD on each sub-square)

D、fmvg：MV magnitude（就是MV的模）

E、fp：Percentage of coefficients cost in RD cost。就是中拉格朗日系数lamda

F、frdc：RD cost of mode Inter_2Nx2N

从A~F的6个特征中选择3个，是通过贪心的sequential forward selection (SFS) algorithm 来选择使互信息量MI最大的3个特征f。

I(F:W)就是互信息量MI。在5个1080p的测试序列上，计算不同f的MI如下表：

fvar、fp和fvsatd都量化成10个取值，所以F有1000个取值，相应有2000个取值，所以是通过特定的方法进行off-line估计，然后存在查找表(LUT)中。

算法简述：

1、Initialize Bayesian threshold in (6) with the QP and resolution settings.

2、RDO process starts from one LCU with CU_depth=0;

3、For the current CU_depth, try mode Inter_2Nx2N, and calculate the feature vector F=[f

var, fp, fvsatd] online;

4、For a feature F, find the class-conditional probability according to pdf p(F|wi) i∈{N, S} in the LUT. Make a decision according to (6). If the Non-SPLIT decision is made, proceed to step 5); otherwise, set CU_depth as CU_depth+1, and then return back to step 3) to perform the RDO process of the four sub-CU;

5、Perform RDO on mode Inter_2NxN, Inter_Nx2N and Intra_2Nx2N (Inter_NxN and Intra_NxN) to decide the optimal mode of the current CU.

6、Exit the RDO process and encode the LCU.

posted @ 2016-07-28 17:02  DwyaneTalk  阅读(...)  评论(... 编辑 收藏