Video coding using motion compensation with polynomial motion vector fields

Abstract

This paper presents novel methods for motion compensated prediction and prediction error coding of video sequences. The scheme utilises segmentation of the video frames into nonregularly shaped segments composed of small square blocks which can be encoded with a very low number of bits. This two-step segmentation is obtained by quadtree-like splitting of image blocks followed by a motion assisted merging algorithm which yields segments characterised by uniformity of motion. Motion fields are compactly encoded using 2-D separable orthonormal polynomials. The number and order of these polynomials is established for each segment separately in an adaptive manner. To improve the efficiency of coding of the residual error, after motion compensated prediction the proposed scheme utilises the spatial properties of the prediction frame available in the encoder and the decoder. Results of the simulations described in this paper show that the presented scheme enables up to 45% bitrate reductions compared to the ITU-T Rec. H.263 video coder while achieving the same objective quality of coded video.