Current techniques for codingimages and video sources with resilience to channel errors can remove much of the need for complex high-redundancy channel coding and provide a graceful degradation of performance with de...
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Current techniques for codingimages and video sources with resilience to channel errors can remove much of the need for complex high-redundancy channel coding and provide a graceful degradation of performance with decreasing channel quality. The main function of these error-resilient techniques is to reduce the propagation of errors within the decoded data. Two main techniques are discussed in detail in this paper: the error-resilient entropy code (EREC) and pyramid vector quantisation (PVQ). The paper concludes with a brief comparison of the relative merits of these systems and areas for further consideration.
A combined source/channel coding scheme without explicit error protection is proposed to transmit images through binary noisy channels. Unlike the error protection with re-transmission scheme and error concealment sch...
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A combined source/channel coding scheme without explicit error protection is proposed to transmit images through binary noisy channels. Unlike the error protection with re-transmission scheme and error concealment scheme by inserting synchronization codewords to entropy-coded bitstream, the proposed coding scheme employs transform coding, fixed-rate uniform threshold trellis coded quantization (UTTCQ) and optimal bit allocation algorithm (BAA) to organize the bitstream in a way that is less sensitive to channel noise, achieving data compression and error resilience at the same time. An image is first block transformed to the frequency domain and the same frequency components in different blocks are grouped together as a single subsource. Every subsource is then quantized by a uniform threshold trellis coded quantizer constructed based on the mean and variance of the subsource. Steepest descent method and iterative scheme are employed to determine the optimum bit allocation among the subsources subject to the constraints of the average coding rate and allowable bits to each sample. The coding system uses no error protection, no synchronization codewords and no entropy coding. However, it shows decent compression ratio and gracious degradation with respect to increasing channel errors. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
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