A new motion compensation method for image sequence coding using hierarchical grid interpolation

Presents a new motion estimation method for low bit-rate image sequence coding that uses a hierarchical decomposition of the current image frame to describe scene motion in terms of displacement and deformation of variable-sized rectangular regions. Because the conventional blockmatching motion compensation method (BMA) can only cope with the problem of translational movement of the scene, some researchers have proposed deformable-block-based motion compensation such as control grid interpolation (CGI) and the triangle-based method (TBM). CGI begins with a spatial displacement for a small number of points in an image, termed control points. TBM partitions the image frame into triangular patches with equal size that are deformable during the motion compensation. These methods do not consider using the different motion characteristics and the shape properties of the moving objects, but instead apply the same motion estimation algorithm to every part of the scene which may be stationary or moving. The present authors propose a new motion compensation method called hierarchical grid interpolation (HGI) which segments a frame into various quadrangles with different sizes (described by quadtree segmentation) according to the motion activity. In the experiments, the authors compare HGI with the conventional BMA and TBM. HGI requires less computation, produces less prediction error, and requires lower transmission bit-rate. It also achieves a subjective image quality that is better than the conventional motion compensation coder