Constrained Viterbi Algorithm and its Application in Error Resilient Transmission of SPIHT Coded Images

The Viterbi algorithm (VA) is well-known to be an optimum decoding method for channels with random error patterns. But the decoding complexity grows greatly while the memory size increases and it doesn´t work while burst errors occurs. Constrained Viterbi algorithm (C-VA) was proposed in a novel product code scheme (Lei Cao and Chang Wen Chen, 2003) to overcome those drawbacks. The main idea of C-VA is to make full use of those bits known to be decoded correctly first. It has been proved in Lei Cao and Chang Wen Chen (2003) that once reliable constraint conditions can be given, the C-VA works well in normal image transmission. In this paper, a new scheme is proposed for error resilient transmission of set partitioning in hierarchical trees (SPIHT) coded images by adding constraint condition directly and simply. Experiments show that the C-VA is very useful under the extremely inferior channel conditions if the best quality of reconstructed images can be sacrificed.