Driven by a host of emerging applications (e.g., sensor networks and wireless video), distributed source coding (i.e., Slepian-Wolf coding, Wyner-Ziv coding and various other forms of multiterminal source coding), has recently become a very active research area. In this thesis, we first design a practical coding scheme for the quadratic Gaussian Wyner-Ziv problem, because in this special case, no rate loss is suffered due to the unavailability of the side information at the encoder. In order to approach the Wyner-Ziv distortion limit D??W Z(R), the trellis coded quantization (TCQ) technique is employed to quantize the source X, and irregular LDPC code is used to implement Slepian-Wolf coding of the quantized source input Q(X) given the side information Y at the decoder. An optimal non-linear estimator is devised at the joint decoder to compute the conditional mean of the source X given the dequantized version of Q(X) and the side information Y . Assuming ideal Slepian-Wolf coding, our scheme performs only 0.2 dB away from the Wyner-Ziv limit D??W Z(R) at high rate, which mirrors the performance of entropy-coded TCQ in classic source coding. Practical designs perform 0.83 dB away from D??W Z(R) at medium rates. With 2-D trellis-coded vector quantization, the performance gap to D??W Z(R) is only 0.66 dB at 1.0 b/s and 0.47 dB at 3.3 b/s. We then extend the proposed Wyner-Ziv coding scheme to the quadratic Gaussian multiterminal source coding problem with two encoders. Both direct and indirect settings of multiterminal source coding are considered. An asymmetric code design containing one classical source coding component and one Wyner-Ziv coding component is first introduced and shown to be able to approach the corner points on the theoretically achievable limits in both settings. To approach any point on the theoretically achievable limits, a second approach based on source splitting is then described. One classical source coding component, two Wyner-Ziv coding components, and a linear estimator are employed in this design. Proofs are provided to show the achievability of any point on the theoretical limits in both settings by assuming that both the source coding and the Wyner-Ziv coding components are optimal. The performance of practical schemes is only 0.15 b/s away from the theoretical limits for the asymmetric approach, and up to 0.30 b/s away from the limits for the source splitting approach.

This thesis addresses the optimal scalar quantizer design for two problems, i.e. the two-stage Wyner-Ziv coding problem and the multiple description coding problem for finite-alphabet sources. The optimization problems are formulated as the minimization of a weighted sum of distortions and rates. The proposed solutions are globally optimal when the cells in each partition are contiguous. The solution algorithms are both based on solving the single-source or the all-pairs minimum-weight path (MWP) problems in certain weighted directed acyclic graphs (WDAG). When the conventional dynamic programming technique is used to solve the underlying MWP problems the time complexity achieved is $O(N^3)$ for both problems, where $N$ is the size of the source alphabet. We first present the optimal design of a two-stage Wyner-Ziv scalar quantizer with forwardly or reversely degraded side information (SI) {for finite-alphabet sources and SI}. We assume that binning is performed optimally and address the design of the quantizer partitions. A solution based on dynamic programming is proposed with $O(N^3)$ time complexity. %The solution relies on finding the single-source or the all-pairs MWP in several one dimensional WDAGs. Further, a so-called {\it partial Monge property} is additionally introduced and a faster solution algorithm exploiting this property is proposed. Experimental results assess the practical performance of the proposed scheme. Then we present the optimal design of an improved modified multiple-description scalar quantizer (MMDSQ). The improvement is achieved by optimizing all the scalar quantizers. %are optimized under the assumption that all the central and side quantizers have contiguous codecells. The optimization is based on solving the single-source MWP problem in a coupled quantizer graph and the all-pairs MWP problem in a WDAG. Another variant design with the same optimization but enhanced with a better decoding process is also presented to decrease the gap to theoretical bounds. Both designs for the second problem have close or even better performances than the literature as shown in experiments. / Thesis / Master of Applied Science (MASc)

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published_or_final_version / Obstetrics and Gynaecology / Doctoral / Doctor of Philosophy

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Multipulse-excitation has greatly improved the speech quality achievable from linear predictive coders which previously required speech to be classified as voiced or unvoiced for excitation purposes. Multipulse removes the need for voicing classification, improving speech quality by enhancing the excitation and offsetting errors in the vocal tract filter. An investigation of multipulse-excitation applied to a channel vocoder and a formant synthesiser was conducted. The prime objective was to improve the performance of these algorithms and achieve multipulse linear prediction speech quality, our target quality. This dissertation outlines and restates the idea of multipulse-excitation applied to a linear predictive vocoder. We then examine a high quality channel vocoder and formant synthesiser, and the use of multipulse-excitation to improve their performances. In each case time and frequency domain multipulsecalgorithms were used. Various modifications were made to these algorithms in order to accommodate multipulse-excitation and improve the overall speech quality. In the case of the channel vocoder this involved a novel technique, which sacrificed the inherent waveform preserving properties of the multipulse algorithm. Only by increasing both the pulse rate and the number of channels could the multipulse-excited channel vocoder achieve our target quality. With the formant synthesiser it was possible, by variation of the pulse rate alone, to achieve our target quality. Comparisons are drawn between the three multipulse algorithms and reasons given for their differing performance; this is substantiated by experimental results. These results suggested interesting improvements to the multipulse-excited formant synthesiser; and also hinted at a new and novel technique for formant tracking, using multipulse-excitation applied to a formant synthesiser.

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