Advanced FGS Coding Scheme Based on MPEG-4 FGS Technology

In this paper, we propose an advanced FGS coding scheme based on MPEG-4 FGS technology. 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. Using this residual signal, 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. Moreover, the residue input signal to the enhancement layer shows a sharper distribution with less entropy for the DCT coefficients. Based on the sharper distribution, a new set of VLC tables are established for improved bit-plane coding. It is shown by simulations that the proposed FGS coding scheme provides better coding performance than the MPEG-4 FGS coding.