Pixel-based Extraction of Moving Objects for Sprite Coding

In this paper, a method to extract moving objects on a pixel base for MPEG-4 “sprite coding” is proposed. Sprite coding is a form of object coding: it uses a unified panoramic background image derived from a sequence having a camera motion, and a foreground object as video object planes (VOP’s). The proposed algorithm utilizes background difference, which is the difference between the original image and the background image, and watershed transform to extract the foreground moving objects. We first apply background difference to generate a foreground candidate image. Then, watershed transform is applied to this candidate image to extract the contours of the foreground objects. Furthermore, we utilize the macroblock mask of the foreground objects, which is generated by the conventional method, to delete the unnecessary edges extracted by watershed transformation. Results given by our proposed method are more than twice as better than that of the conventional method.