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Articles by Dong-Xiao Li
Total Records ( 3 ) for Dong-Xiao Li
  Zheng Zhu , Dong-Xiao Li and Ming Zhang
  A general methodology for performance modeling and optimization of hierarchical B pictures used in video coding is proposed in this study. First, an approach of directed tree decomposition is used to denote hierarchical B pictures. In combination with a proposed linear model for compression efficiency, the performance of any hierarchical B prediction structure can be evaluated conveniently from the directed tree. Then with a dynamic programming method, the optimal tree for any group length of hierarchical B pictures can be set up elegantly from recursive subtrees. This method can be adapted to tradeoff between compression efficiency and random access ability. Besides, experimental results show that the optimal tree of compression efficiency achieves higher performance than the existing hierarchical B prediction structures.
  Li Yao , Dong-Xiao Li and Ming Zhang
  Dense depth maps provide significant geometry information for 3D video and free viewpoint video systems. Traditional stereo correspondence methods usually deal with each stereo image pair separately. As a result, the generated depth sequence is temporally inconsistent. This paper presented a novel approach to recover spatio-temporally consistent depth maps. The proposed method first applied sequential belief propagation algorithm to achieve an approximate minimum of spatial energy on Markov random fields. Then in temporal domain, a smoothness cost along optical flow was incorporated between consecutive frames. The combined cost which determined the disparity value was passed forward and temporal consistency was enforced during the process. In addition, the streamlined implementation was time and memory efficient. In experimental validation, quantitative evaluation as well as subject assessment was performed on several test datasets. The results showed that the proposed method yielded temporally consistent depth sequence and reduced flickering artifacts in the synthesized view while maintaining visual quality.
  Lingshan Liu , Ming Xi , Dong-Xiao Li and Ming Zhang
  Precision of depth has a significant impact on quality of virtual view synthesis in 3DTV system. Artifacts exist in stereo correspondence. Object boundary artifact is one of the most difficult problems. The object boundary pixels receive colors from both foreground and background thus leads to wrong mapping. The occlusion fill-up process causes object boundary expansion which makes boundary pixels unreliable. We propose a boundary matting technique based on natural image matting algorithms to calculate the alpha value of the boundary pixels. Depth values which are suggested by alpha values can be recalculated. The limitation of matting algorithms is that they define only boundaries between two layers and cannot solve the multiple-layer definition problem. Our contribution is the localized methods of boundary matting which can solve the multiple layer boundaries in complex depth map. Our goal is superior view synthesis from stereo, thus the quality of virtual views are valued in experiments. The result shows that our technique reduces the boundary artifacts effectively.
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