Scene Adaptive Multiple Coding Scheme for Robust
Chang Cao, Wen Chen · 2000
In this paper, we propose a combined source and channel coding scheme for image trammission over noisy channels. The key com- ponent is extracting and preserving the scene information and incorporat- ing it with unequal error protection to combat the channel errors. After hierarchical wavelet decomposition of the image, wavelet coefficients with parent-child relationship are grouped into wavelet blocks and classified according to corresponding scenes in the original image. For each class, spatial neighborhood coefficients in the high frequency subbands are con- strained so that the spatially isolated coefficients are removed and clus- tered coefficients are retained at the same time. All the wavelet blocks in the same class are grouped together and coded using SPIHT algorithm. High source coding efficiency is preserved even though multiple source coded bitstreams are generated since the wavelet tree structure is untact. In order to combat the channel errors, unequal error protection strategy implemented by RCPClCRC channel coding is designed based on the bit contribution to both PSNR and human visual sensitivity. Finally, a post- processing method is developed at the receiving end to restore the degra- dation due to the residual error after channel decoding. Experimental results show that the proposed scheme is indeed able to provide protection for more important bits and more important visual content under noisy transmission environment. In particular, the reconstructed images illus- trate consistently better visual quality. Keywords-Scene Adaptive, Classification, Multiple hierarchy, SPIHT, RCPC, CRC, Wireless Channel.