Analysis of Shape Coding Approaches Used in MPEG-4

In this paper, a comparative study of shape-coding approaches dealing with "shape from contours" family of techniques used in MPEG-4 is presented. The research focuses on four coding methods; chain code, signature, skeleton and splitting. The analysis includes the relation between bit rate and distortion. The study allows for a more flexible tradeoff between approximation error and bit budget. An operational rate-distortion (ORD), providing tradeoff, is calculated at different levels using different coding methods. A comprehensive comparison, based on the results of using coding methods, shows the capability of each method for different objects normal and complex- at different levels. Modifications have been done in signature method to deal with complicated objects.