Multiple description coding based on multiple bitstream wavelet zero tree image compression
Chen, Chang Wen
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Multiple description coding (MDC) is a well-known robust data compression algorithm designed to minimize the distortion caused by data loss in packet-based communication systems. Several MDC schemes for transmitting wavelet compressed images have been developed. However, these MDC schemes cannot be adopted for digital mobile wireless applications where both packet loss and bit error are present, because individual description in these MDC schemes usually does not have adequate error resilience capability to combat the bit error in transmission. In this paper, we propose an algorithm to achieve robust communication over error prone transmission channels with both packet loss and bit error. We integrate the multiple description scalar quantization (MDSQ) with the multiple wavelet tree image coding method in order to provide an excellent error resilient capability. Two descriptions are generated independently by using index assignment of MDSQ. For each description, multiple sub-sampling is applied to split the wavelet coefficients of the source image into multiple sub-sources. Each sub-source is then entropy coded using the SPIHT algorithm and followed by a channel coding scheme that combines cyclic redundancy code (CRC) and rate compatible punctured convolutional (RCPC) code to offer unequal error protection to the entropy coded bits. The unequal error protection channel coding rate is designed based on the bit error sensitivity of different bit planes to achieve maximum end-to-end quality of service. Experimental results show that the proposed scheme not only exhibits an excellent error resilient performance but also demonstrates graceful degradation over error prone channels with changing rate of packet loss and bit error.