Context based optimal shape coding
This paper investigates how context-based DPCM techniques can be used in conjunction with an operationally rate-distortion (ORD) optimized shape coder. Object contours are approximated by connected second-order spline segments, each defined by three consecutive control points, and, in the case of the inter mode, by segments of the motion-compensated reference contours. In scalable intra mode and non-scalable inter mode shape coding, consecutive control points are encoded predictively, using an angle and run framework, with respect to corresponding contexts in the reference frame and the base layer, respectively. We employ a novel criterion for selecting global object motion vectors in the inter mode, which further improves efficiency.