An efficient boundary encoding scheme which is optimal in the rate distortion sense

A major problem in object oriented video coding is the efficient encoding of the shape information of arbitrarily shaped objects. Efficient shape coding schemes are also needed in encoding the shape information of video object planes (VOP) in the MPEG-4 standard. In this paper, we present an efficient method for the lossy encoding of object shapes which are given as 8-connect chain codes (Meier et al., 1997). We approximate the object shape by a second order B-spline curve and consider the problem of finding the curve with the lowest bit rate for a given distortion. The presented scheme is optimal, efficient and offers complete control over the trade-off between bit-rate and distortion. We present results with the proposed scheme using objects shapes of different sizes.