| With the development of video technology,3D video technology applications are being used more widely.As the extension of well-known video coding standard High Efficiency Video Coding(HEVC),3D High Efficiency Video Coding(3D-HEVC)is currently the latest 3D video coding standards.3D-HEVC adopts multi-view video plus depth as a new format.Using Depth-Image-Based Rendering,where a small number of video captured from different view-points and associated depth maps are synthesized for extra view sequence.Therefore,depth image vedio coding is extremely important in 3D-HEVC vedio coding.As the core module of video coding,Intra coding directly impacts the performance of entire encoder.Research shows that the intra depth coding takes about 5 to 10 times more than that of texture view,and contributes the most of complexity for 3D-HEVC.In order to reduce the complexity of depth image coding,this paper focuses on the fast algorithm of intra depth coding.The major contributions of this paper are summarized as follows:First,considering heavy computational burden of quad-tree recursive for intra depth coding,this paper proposes two fast algorithm based on depth map layer to reduce the complexity of intra depth coding.The first one is early PU splitting of intra depth coding,which is based on minimum cost value of 35 HEVC intra prediction modes and minimum cost value of the DMMs to determine whether skipping the refined procedure with current PU or DMMs.When the QP of depth map is 34,this algorithm can reduce 11.16% complexity reduction of total video coding.The second algorithm is early PU pruning of intra depth coding,which is bases on the refining results of intra depth coding to determine whether stopping current PU’s downward parititon.Compared with the reference softwore HTM 13.0 of 3D-HEVC,although early PU pruning algorithm can reduce 39.06% overall coding time averagely,while an obvious degeradation of coding performance about 1.41% BD-rate increasing is caused for synthesized views.Therefore,an improved algorithm of early PU pruning of intra depth coding is presented,which divides the best mode from refined process into mode 0/1 and Leftovers,and two thresholds are set to decide whether terminating downward parititon.Experimental results indicate that the improved algorithm can reduce 37.57% computional cost of total video coding.As for the coding performance,0.60% BD-rate increasing is caused for synthesized views,which is better than previous algorithm.Second,a fast algorithm based on mode is proposed to solve the problem of high complexity in the a large number of intra depth coding mode.When the best mode in rough search is Planar and DMMs calculation is skipped,mode-based fast algorithm selects Planar mode as the best mode of current PU,directly skipping the process of the refined mode decision.Compared with HTM 13.0,experimantal results indicates that mode-based fast algorithm can achieve an average of 13.43% complexity of total video coding without increasing BD-rate value of synthesized views(nearly no performance degredation).In the end,this paper combines abovementioned algorithm and after numerable experiments,the proposed algorithm can achieve an average of 48.31% complexity of total video coding and 55.63% complexity reduction for intra depth coding.For the coding performance,0.76% BD-rate increasing is caused for synthesized views.Banlacing the intra depth coding capacity and complexity,the computational burdens of the proposed algorithms are significantly reduced under the premise of guaranteed coding performance. |
