An Advanced FGS Coding Scheme Based on MPEG-4 FGS Technology

Abstract

In this paper, we propose an advanced FGS coding scheme based on MPEG-4 FGS technology. The general structure of the proposed FGS coding scheme is based on the standard MPEG-4 FGS. To enhance the coding efficiency of the MPEG-4 FGS coding, the proposed FGS coding incorporates two new coding techniques. Firstly, the proposed FGS enhancement-layer encoder takes as input the difference between the original DCT coefficient and the decision level of the quantizer instead of the difference between the original DCT coefficient and its reconstruction level. By this approach, the sign information of the enhancement-layer DCT coefficients can be the same as that of the base-layer ones at the same frequency index in DCT domain. Thus, overhead bits required for coding a lot of sign information of the enhancement-layer DCT coefficients in bit-plane coding can be removed from the generated bitstream. Second, the residue input signal to the enhancement layer shows a sharper distribution with less entropy or energy for the DCT coefficients by the proposed technique. The improvement in entropy is directly utilized by the proposed coding scheme to establish a new set of VLC tables for bit-plane coding. It is shown by simulations that the proposed FGS coding scheme provides better coding performance, compared to the MPEG-4 FGS in terms of compression efficiency.