Error-resilient wavelet tree coding for robust image transmission

Abstract

In this paper, a scheme for robust image coding and transmission over noisy channels is presented. First, the spatial-orientation trees in wavelet domain are independently encoded using the algorithm of set partitioning in hierarchical trees (SPIHT). We generate multiple bitstreams in order to limit the error propagation. Because the self-similarity across subbands is preserved in each wavelet tree, a high coding efficiency is also obtained. However, when these bitstreams with variable length are transmitted sequentially, error impact may still be propagated across the boundaries between two consecutive bitstreams and may cause catastrophic decoding. Therefore, we apply error resilient entropy coding (EREC) to reorganize these bitstreams into fixed length slots so that synchronization of the start of each bitstream is automatically achieved at the receiver. This is particularly useful for the progressive data where bits located at the beginning of bitstream are always more important than those at the end. Finally, to further alleviate the impact of errors in the beginning of the bitstreams, parity bits are added and exploited by an error concealment technique conducted only in the lowest frequency subband. Experimental results demonstrate an excellent error resilient performance of the proposed scheme.