A Fast Mode Selection For DMMs Of Depth Map Intra Coding In 3D-HEVC

With the development of the times,conventional 2 division video has became unable to meet the need of people in life and entertainment.The pursuit of 3D(3 Division,3D)video seems to be a popular direction in today's video development.And the 3D game is a typical representative for this tendency.In 2015,the ITU-T and ISO release the 3D-HEVC standard based on the HEVC standard.To compress 3 division videos more effectively,the multi view and depth map are adopted in 3D-HEVC standard.The depth map has large flat areas and sharp edges.To improve the quality of the compressed video,some intra prediction modes(depth modeling modes,DMM)for depth map are introduced in 3D-HEVC.There are two modes included in DMMs,DMM1 and DMM4.In DMM1 mode,there are too many different partitions for coding units.For example,the number of partitions for 32x32 coding units in DMM1 is 368.So,the calculations of the DMM modes are much more than that of the conventional intra modes.Compared to conventional intra modes,the DMMs improve the quality of the video and the increase the complexity of the intra coding.This brings much difficulties to application and obstructs the population of the 3D-HEVC.In this paper,the intra prediction modes of depth map in 3D-HEVC are studied and the complexity are analyzed.Fast algorithm is proposed to reduce the complexity in this paper,including reducing unneeded DMMs and simplifying the DMM1's searching.The first part is the DMMs skipping in 3D-HEVC.By changing the processing order of the rough searching of conventional intra modes and the DMMs,the refined searching results(RD-costs)of the conventional intra modes are used to decide whether the DMMs can be skipped.If the RD-cost of the best conventional intra mode is small enough,we can skip the DMMs calculations;otherwise,the calculations of DMMs will be done.Compared with the methods with the same type,the refined result of the conventional intra mode is used in the proposed method and the estimation is more accurate.What's more,the method can be combined with other methods,like variance method,to reduce more encoding time.The second parts is the simplifying of the DMM1's searching in 3D-HEVC.According to the features of the partitions,the golden ratio and three iterations are adopted to simplify the searching in DMM1.This avoids going through all the partitions in DMM1 and much time is saved.Compared with the methods with the same type,smaller number of the DMM1 partitions should be searched and more encoding time can be saved.In order to verify the validity of the proposed algorithm,8 sets of official standard test sequences are adopted in our training and test.The sequences include two kinds of resolution,1024x768 and 1920x1080.Three views plus depth map and all intra configuration are adopted in our experiments.The four sets QPs are(25,34),(30,39),(35,42),(40,45).The two aspects of the algorithm are tested.The DMMs' skipping method can reduce 32.09% intra coding time with 0.06% BD-rate increasing;the method of simplifying of the DMM1's searching can reduce 70.44% DMM1 searching time with 0.22 BD-rate increasing.In the case of maintaining the same coding performance loss,the two methods proposed can reduce more encoding time or DMM1 searching time compared with the methods with the same type.Finally,these two methods are combined in our experiments.Overall,the algorithm proposed in this paper reduces 37% encoding time with only 0.4% BD-rate increasing.