On-line sprite encoding with large global motion estimation
Summary form only given. A sprite which is an image composed of pixels belonging to a video object visible throughout a video segment is a very important concept proposed by MPEG4. Because of the search region limitation in the global motion estimation, the performance of traditional sprite coding technology is not satisfactory in the case of fast camera motion. Only enlarging the search region is difficult to ensure the right motion estimation. An improved algorithm is proposed with enlarging the search region, predicting the motion of the current VOP (video object plane) and shortening the iterative time. Three main techniques are adopted in the new algorithm. They are: (1) enlarging search region; (2) weighting sum of absolute difference (SAD); and (3) shortening iteration. Two group experiments present a comparison between the original algorithm and the improved algorithm. The first group experiment shows the improved algorithm gets the same performance as the original algorithm in coding the general motion sequences. In the second group experiment, the Stefan background sequences which frame rates of 15 Hz, 10 Hz, 7.5 Hz, and 6 Hz are encoded in various transformations. The results given in a table show the coding performances of the algorithm are significantly improved.