Scalable ideal-segmented chain coding

In this paper, we present an optimal chain-code-like representation to code contour shapes; in addition, this representation can be easily extended to as a scalable form which structures shape data as the base layer followed by two enhancement layers. Lossy coding scheme is also presented for low-bit-rate applications. Compared with the block-based CAE method in MPEG-4 and DCC with arithmetic coder, our method not only has the higher compression ratio with less computation steps, but also can be applied to layered transmission. The scalability achieved by our scheme can be recognized in both spatial and quality-wise. Compared with another scalable shape coding methods, our scheme is simple but more efficient than progressive polygon encoding methods. In case of the base layer with distortion Dn = 0.02, our scheme saves about 20∼30% amount of bits, that is, we have a smaller size base layer, which is important in layered transmission.