Optimal 2-D hierarchical content-based mesh design and update for object-based video

Representation of video objects (VOs) using hierarchical 2-D content-based meshes for accurate tracking and level of detail (LOD) rendering have been previously proposed, where a simple suboptimal hierarchical mesh design algorithm was employed. However, it was concluded that the performance of the tracking and rendering very much depends on how well each level of the hierarchical mesh structure fits the VO under consideration. To this effect, this paper proposes an optimized design of hierarchical 2-D content-based meshes with a shape-adaptive simplification and a temporal update mechanism for object-based video. Particular contributions of this work are: (1) analysis of optimal number of nodes for the initial fine level-of-detail mesh design; (2) adaptive shape simplification across hierarchy levels; (3) optimization of the interior-node decimation method to remove only a maximal independent set to preserve Delaunay topology across hierarchy levels for better bitrate versus quality performance; and (4) a mesh-update mechanism which serves to update a temporally 2-D dynamic mesh in case of occlusion due to 3-D motion and self-occlusion. The proposed optimized and temporally updated hierarchical mesh representation can be applied in object-based video coding, retrieval, and manipulation.