Error Resilient Image Transmission Based on Virtual SPIHT

摘要

SPIHT is one of the most efficient image compression algorithms. It had been successfully applied to a wide variety of images, such as medical and remote sensing images. However, it is highly susceptible to channel errors. A single bit error could potentially lead to decoder derailment. In this paper, we integrate new error resilient tools into wavelet coding algorithm and present an error-resilient image transmission scheme based on virtual set partitioning in hierarchical trees (SPIHT), EREC and self truncation mechanism. After wavelet decomposition, the virtual spatial-orientation trees in the wavelet domain are individually encoded using virtual SPIHT. Since the self-similarity across sub bands is preserved, a high source coding efficiency can be achieved. The scheme is essentially a tree-based coding, thus error propagation is limited within each virtual tree. The number of virtual trees may be adjusted according to the channel conditions. When the channel is excellent, we may decrease the number of trees to further improve the compression efficiency, otherwise increase the number of trees to guarantee the error resilience to channel. EREC is also adopted to enhance the error resilience capability of the compressed bit streams. At the receiving side, the self-truncation mechanism based on self constraint of set partition trees is introduced. The decoding of any sub-tree halts in case the violation of self-constraint relationship occurs in the tree. So the bits impacted by the error propagation are limited and more likely located in the low bit-layers. In additional, inter-trees interpolation method is applied, thus some errors are compensated. Preliminary experimental results demonstrate that the proposed scheme can achieve much more benefits on error resilience.