This correspondence focuses on a significant distinction between two hierarchical type covering strategies, namely, weak and strong covering, and on the impact of this distinction on known results. In particular, it i...
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This correspondence focuses on a significant distinction between two hierarchical type covering strategies, namely, weak and strong covering, and on the impact of this distinction on known results. In particular, it is demonstrated that the rate region for weak covering, whose natural use is in scalable source coding, is generally larger than the rate region for strong covering, which is primarily useful in hierarchical guessing. This correspondence also presents a corrected converse result for the hierarchical guessing problem.
Rate-distortion bounds for scalablecoding, and conditions under which they coincide with nonscalable bounds, have been extensively studied. These bounds have been derived for the general tree-structured refinement sc...
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Rate-distortion bounds for scalablecoding, and conditions under which they coincide with nonscalable bounds, have been extensively studied. These bounds have been derived for the general tree-structured refinement scheme, where reproduction at each layer is an arbitrarily complex function of all encoding indexes up to that layer. However, in most practical applications (e.g., speech coding) "additive" refinement structures such as the multistage vector quantizer are preferred due to memory limitations. We derive an achievable region for the additive successive refinement problem, and show via a converse result that the rate-distortion bound of additive refinement is above that of. tree-structured refinement. Necessary and sufficient conditions for the two bounds to coincide are derived. These results easily extend to abstract alphabet sources under the condition E {d(X, a)} < infinity for some letter a. For the special cases of square-error and absolute-error distortion measures, and subcritical distortion (where the Shannon lower bound (SLB) is tight), we show that successive refinement without rate loss is possible not only in the tree-structured sense, but also in the additive-coding sense. We also provide examples which are successively refinable without rate loss for all distortion values, but the optimal refinement is not additive.
This correspondence focuses on a significant distinction between two hierarchical type covering strategies, namely, weak and strong covering, and on the impact of this distinction on known results. In particular, it i...
详细信息
ISBN:
(纸本)0780382803
This correspondence focuses on a significant distinction between two hierarchical type covering strategies, namely, weak and strong covering, and on the impact of this distinction on known results. In particular, it is demonstrated that the rate region for weak covering, whose natural use is in scalable source coding, is generally larger than the rate region for strong covering, which is primarily useful in hierarchical guessing. This correspondence also presents a corrected converse result for the hierarchical guessing problem.
The common practice for achieving unequal error protection (UEP) in scalable multimedia communication systems is to design rate-compatible punctured channel codes before computing the UEP rate assignments. This paper ...
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The common practice for achieving unequal error protection (UEP) in scalable multimedia communication systems is to design rate-compatible punctured channel codes before computing the UEP rate assignments. This paper proposes a new approach to designing powerful irregular repeat accumulate (IRA) codes that are optimized for the multimedia source and to exploiting the inherent irregularity in IRA codes for UEP. Using the end-to-end distortion due to the first error bit in channel decoding as the cost function, which is readily given by the operational distortion-rate function of embedded source codes, we incorporate this cost function into the channel code design process via density evolution and obtain IRA codes that minimize the average cost function instead of the usual probability of error. Because the resulting IRA codes have inherent UEP capabilities due to irregularity, the new IRA code design effectively integrates channel code optimization and UEP rate assignments, resulting in source-optimized channel coding or joint source-channel coding. We simulate our source-optimized IRA codes for transporting SPIHT-coded images over a binary symmetric channel with crossover probability p. When p = 0.03 and the channel code length is long (e.g., with one codeword for the whole 512 x 512 image), we are able to operate at only 9.38% away from the channel capacity with code length 132380 bits, achieving the best published results in terms of average peak signal-to-noise ratio (PSNR). Compared to conventional IRA code design (that minimizes the probability of error) with the same code rate, the performance gain in average PSNR from using our proposed source-optimized IRA code design is 0.8759 dB when p = 0.1 and the code length is 12800 bits. As predicted by Shannon's separation principle, we observe that this performance gain diminishes as the code length increases.
Rate-distortion bounds for scalablecoding, and conditions under which they coincide with nonscalable bounds, have been extensively studied. These bounds have been derived for the general tree-structured refinement sc...
详细信息
Rate-distortion bounds for scalablecoding, and conditions under which they coincide with nonscalable bounds, have been extensively studied. These bounds have been derived for the general tree-structured refinement scheme, where reproduction at each layer is an arbitrarily complex function of all encoding indexes up to that layer. However, in most practical applications (e.g., speech coding) "additive" refinement structures such as the multistage vector quantizer are preferred due to memory limitations. We derive an achievable region for the additive successive refinement problem, and show via a converse result that the rate-distortion bound of additive refinement is above that of. tree-structured refinement. Necessary and sufficient conditions for the two bounds to coincide are derived. These results easily extend to abstract alphabet sources under the condition E {d(X, a)} < infinity for some letter a. For the special cases of square-error and absolute-error distortion measures, and subcritical distortion (where the Shannon lower bound (SLB) is tight), we show that successive refinement without rate loss is possible not only in the tree-structured sense, but also in the additive-coding sense. We also provide examples which are successively refinable without rate loss for all distortion values, but the optimal refinement is not additive.
To provide unequal erasure protection to scalable codes, a general framework has been proposed in [1] and it has become the foundation of following research in this literature. In this paper, we make opportunistic uti...
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ISBN:
(纸本)9781605586212
To provide unequal erasure protection to scalable codes, a general framework has been proposed in [1] and it has become the foundation of following research in this literature. In this paper, we make opportunistic utilization of received packets under the same framework. Specifically, we extract those non-decodable original symbols in received packets by taking advantage of the joint coding structure. By regulating the scalable codes to partially-decodable scalable codes, these original symbols can be used to improve the quality of reconstructed source. Further more, we formulate the opportunistic unequal erasure protection and analyze the relationship between optimal unequal erasure protection (OP) and opportunistic optimal unequal erasure protection (OOP). Based on the analysis result, a simple algorithm is proposed to find the optimal protection which maximizes the expected quality of reconstructed source. Finally, experiment results are presented which verify the improvement of opportunistic utilization over traditional unequal erasure protection.
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