Efficient motion estimation and coding for arbitrary-shaped video objects
We extend quad-tree-structured variable size block matching (VSBM) techniques for the estimation of motion in arbitrary-shaped video objects. Coding efficiency is significantly improved over recently developed object-based coding schemes that employ fixed size block matching (FSBM). Evaluation on MPEG-4 video object test sequences show that inherent motion is represented by considerably fewer blocks for similar prediction quality. Motion vectors are differentially encoded using a 2-D predictor, and further coding efficiencies are gained by exploiting the spatial redundancy of vector information. VSBM is extended to exploit areas of uniform motion within video objects. This modified VSBM (MVSBM) technique is shown to outperform both FSBM and VSBM for small objects with a high degree of disparate motion. Finally, a technique that minimizes temporal redundancies for the VSBM and MVSBM data structures is presented. Overall savings of up to 21% are achieved in coding the motion information, including tree descriptions and other overheads. (C) 2001 Academic Press.
video coding motion compensation 2d video objects