Thesis (M. Sc. (Computer Science)) --University of Limpopo, 2019 / A Text-to-speech (TTS) synthesis system is a software system that receives text as input and produces speech as output. A TTS synthesis system can be used for, amongst others, language learning, and reading out text for people living with different disabilities, i.e., physically challenged, visually impaired, etc., by native and non-native speakers of the target language. Most people relate easily to a second language spoken by a non-native speaker they share a native language with. Most online English TTS synthesis systems are usually developed using native speakers of English. This research study focuses on developing accented English synthetic voices as spoken by non-native speakers in the Limpopo province of South Africa. The Modular Architecture for Research on speech sYnthesis (MARY) TTS engine is used in developing the synthetic voices. The Hidden Markov Model (HMM) method was used to train the synthetic voices. Secondary training text corpus is used to develop the training speech corpus by recording six speakers reading the text corpus. The quality of developed synthetic voices is measured in terms of their intelligibility, similarity and naturalness using a listening test. The results in the research study are classified based on evaluators’ occupation and gender and the overall results. The subjective listening test indicates that the developed synthetic voices have a high level of acceptance in terms of similarity and intelligibility. A speech analysis software is used to compare the recorded synthesised speech and the human recordings. There is no significant difference in the voice pitch of the speakers and the synthetic voices except for one synthetic voice.

Begränsad processor- och minneskapacitet är en stor utmaning för loggning avsensorsignaler i motorstyrenheter. För att kunna lagra större mängder data i dessakan komprimering användas. För att kunna implementera komprimering imotorstyrenheter krävs det att algoritmerna klarar de begränsningar som finnsgällande processorkapaciteten och ändå kan producera en godtagbarkomprimeringsgrad.Denna avhandling jämför komprimeringsalgoritmer och undersöker vilken ellervilka algoritmer som är bäst lämpade för detta ändamål. Detta i syfte att förbättraloggning och därmed effektivisera felsökning. Detta gjordes genom att utveckla ettsystem som kör olika komprimeringsalgoritmer på samplad sensordata frånmotorstyrenheter och beräknar komprimeringstid och komprimeringsgrad.Resultaten visade att delta-på-delta-komprimering presterade bättre än xorkomprimering för dessa data. Delta-på-delta presterade betydligt bättre gällandekomprimeringsgrad medan skillnaderna i komprimeringstid mellan algoritmernavar marginella. Delta-på-delta-komprimering bedöms ha god potential förimplementering i loggningssystem för motorstyrenheter. Algoritmen bedöms somväl lämpad för loggning av mindre tidsserier vid viktiga händelser, för merkontinuerlig loggning föreslås fortsatta studier för att undersöka hurkomprimeringsgraden kan förbättras ytterligare. / Limited processor and memory capacity is a major challenge for logging sensorsignals in engine control units. In order to be able to store larger amounts of data,compression can be used. To successfully implement compression algorithms inmotor control units, it is essential that the algorithms can effectively handle thelimitations associated with processor capacity while achieving an acceptable level ofcompression.This thesis compares compression algorithms on sensor data from motor controlunits in order to investigate which algorithm(s) are best suited to implement forthis application. The work aims to improve the possibilities of logging sensor dataand thus make the troubleshooting of the engine control units more efficient. Thiswas done by developing a system that performs compression on sampled sensorsignals and calculates the compression time and ratio.The results indicated that delta-of-delta compression performed better than xorcompression for the tested data sets. Delta-of-delta had a significantly bettercompression ratio while the differences between the algorithms regardingcompression time were minor. Delta-of-delta compression was judged to have goodpotential for implementation in engine control unit logging systems. The algorithmis deemed to be well suited for logging smaller time series during important events.For continuous logging of larger time series, further research is suggested in orderto investigate the possibility of improving the compression ratio further.

[pt] A transformada de Burrows-Wheeler, baseada na ordenação de contextos, transforma uma seqüência de caracteres em uma nova seqüência mais facilmente comprimida por um algoritmo que explore grandes seqüências de repetições de caracteres. Aliado a recodificação do MoverParaFrente e seguida de uma codificação para os inteiros gerados, eles formam uma nova família de compressores, que possuem excelentes taxas de compressão, com boas performances nos tempos de compressão e descompressão. Este trabalho examina detalhadamente essa transformada, suas variações e algumas alternativas para os algoritmos utilizados em conjunto com ela. Como resultado final, apresentamos uma combinação de estratégias que produz taxas de compressão para texto melhores do que as oferecidas pelas implementações até aqui disponíveis. / [en] The Burrows-Wheeler Transform, based on sorting of contexts, transforms a sequence of characters into a new sequence easier to compress by an algorithm that exploits long sequences of repeted characters. Combined with the coding provided by the MoveToFront Algorithm and followed by a codification for the generated integers, they propose a new family of compressors, that achieve excellent compression rates with good time performances in compression and decompression. This work examines detaildedly this transform, its variations and some alternatives for the algorithms used together with it. As a final result, we present a combination of strategies that producescompression rates for text data that are better than those offered by implementations available nowadays.

O presente trabalho descreve o desenvolvimento de um sistema de tomografia por Ressonância Magnética, para uso em diagnósticos médicos. Ele foi baseado em subsistemas disponíveis comercialmente, tais como os utilizados em equipamentos de imagens de RM comerciais. As principais contribuições deste projeto foram: o desenvolvimento de circuitos eletrônicos complementares e \"software\", necessários para tomar o \"hardware\" adquirido em um Tomógrafo de Ressonância Magnética para diagnósticos médicos. Isso não inclui somente o projeto de complexos programas necessários para gerar os pulsos de RF, formas de onda dos gradientes, sistema de aquisição de dados e as seqüências de pulsos necessárias para o completo sincronismo, mas também o desenvolvimento de uma interface amigável para realizar: a entrada de informações do paciente; a seleção das técnicas de imagem e o \"software\" interativo para visualização e seleção de planos. Um novo algoritmo de compressão de dados, para reduzir o armazenamento necessário de dados de imagens de RM, sem perda de informação foi também apresentado e implementado. Uma comparação com outras implementações de compressão de uso geral foi apresentada para mostrar uma performance superior na taxa de compressão e tempo de execução. / The present work describes the development of a Magnetic Resonance Tomography system to be used for medical diagnostics. It is based on commercially available subsystems such as used as in commercial MRI equipments. The main contributions to the project were: the development of fill up electronics and software needed to turn the acquired hardware into a MR Tomography for medical diagnostics. This includes not only the design of complex software needed to generate the used RF pulses, gradient waveforms, data acquisition system and the desired pulse sequences to synchronize all, but also the development of a user friendly interface to do: the entrance of patient\'s information; the selection of MR imaging techniques and interactive software for image viewing and planes selection. A new data compression algorithm to reduce the storage requirement of raw MR image data without information losses is also presented and implemented. A comparison with others general purpose compression implementations is presented to show the superior performance in the compression rate and execution time.

Error resilience is an important issue when coded video data is transmitted over wired and wireless networks. Errors can be introduced by network congestion, mis-routing and channel noise. These transmission errors can result in bit errors being introduced into the transmitted data or packets of data being completely lost. Consequently, the quality of the decoded video is degraded significantly. This thesis describes new techniques for minimising this degradation. To verify video error resilience tools, it is first necessary to consider the methods used to carry out experimental measurements. For most audio-visual services, streams of both audio and video data need to be simultaneously transmitted on a single channel. The inclusion of the impact of multiplexing schemes, such as MPEG 2 Systems, in error resilience studies is also an important consideration. It is shown that error resilience measurements including the effect of the Systems Layer differ significantly from those based only on the Video Layer. Two major issues of error resilience are investigated within this thesis. They are resynchronisation after error detection and error concealment. Results for resynchronisation using small slices, adaptive slice sizes and macroblock resynchronisation schemes are provided. These measurements show that the macroblock resynchronisation scheme achieves the best performance although it is not included in MPEG2 standard. The performance of the adaptive slice size scheme, however, is similar to that of the macroblock resynchronisation scheme. This approach is compatible with the MPEG 2 standard. The most important contribution of this thesis is a new concealment technique, namely, Decoder Motion Vector Estimation (DMVE). The decoded video quality can be improved significantly with this technique. Basically, this technique utilises the temporal redundancy between the current and the previous frames, and the correlation between lost macroblocks and their surrounding pixels. Therefore, motion estimation can be applied again to search in the previous picture for a match to those lost macroblocks. The process is similar to that the encoder performs, but it is in the decoder. The integration of techniques such as DMVE with small slices, or adaptive slice sizes or macroblock resynchronisation is also evaluated. This provides an overview of the performance produced by individual techniques compared to the combined techniques. Results show that high performance can be achieved by integrating DMVE with an effective resynchronisation scheme, even at a high cell loss rates. The results of this thesis demonstrate clearly that the MPEG 2 standard is capable of providing a high level of error resilience, even in the presence of high loss. The key to this performance is appropriate tuning of encoders and effective concealment in decoders.

<p>Modern semiconductor design methods makes it possible to design increasingly complex system-on-a-chips (SOCs). Testing such SOCs becomes highly expensive due to the rapidly increasing test data volumes with longer test times as a result. Several approaches exist to compress the test stimuli and where hardware is added for decompression. This master’s thesis presents a test data compression method based on a modified facsimile code. An embedded processor on the SOC is used to decompress and apply the data to the cores of the SOC. The use of already existing hardware reduces the need of additional hardware. </p><p>Test data may be rearranged in some manners which will affect the compression ratio. Several modifications are discussed and tested. To be realistic a decompressing algorithm has to be able to run on a system with limited resources. With an assembler implementation it is shown that the proposed method can be effectively realized in such environments. Experimental results where the proposed method is applied to benchmark circuits show that the method compares well with similar methods. </p><p>A method of including the response vector is also presented. This approach makes it possible to abort a test as soon as an error is discovered, still compressing the data used. To correctly compare the test response with the expected one the data needs to include don’t care bits. The technique uses a mask vector to mark the don’t care bits. The test vector, response vector and mask vector is merged in four different ways to find the most optimal way.</p>