Audio Coding Based on Integer Transforms

Die Audiocodierung hat sich in den letzten Jahren zu einem sehr populären Forschungs- und Anwendungsgebiet entwickelt. Insbesondere gehörangepasste Verfahren zur Audiocodierung, wie etwa MPEG-1 Layer-3 (MP3) oder MPEG-2 Advanced Audio Coding (AAC), werden häufig zur effizienten Speicherung und Übertragung von Audiosignalen verwendet. Für professionelle Anwendungen, wie etwa die Archivierung und Übertragung im Studiobereich, ist hingegen eher eine verlustlose Audiocodierung angebracht. Die bisherigen Ansätze für gehörangepasste und verlustlose Audiocodierung sind technisch völlig verschieden. Moderne gehörangepasste Audiocoder basieren meist auf Filterbänken, wie etwa der überlappenden orthogonalen Transformation "Modifizierte Diskrete Cosinus-Transformation" (MDCT). Verlustlose Audiocoder hingegen verwenden meist prädiktive Codierung zur Redundanzreduktion. Nur wenige Ansätze zur transformationsbasierten verlustlosen Audiocodierung wurden bisher versucht. Diese Arbeit präsentiert einen neuen Ansatz hierzu, der das Lifting-Schema auf die in der gehörangepassten Audiocodierung verwendeten überlappenden Transformationen anwendet. Dies ermöglicht eine invertierbare Integer-Approximation der ursprünglichen Transformation, z.B. die IntMDCT als Integer-Approximation der MDCT. Die selbe Technik kann auch für Filterbänke mit niedriger Systemverzögerung angewandt werden. Weiterhin ermöglichen ein neuer, mehrdimensionaler Lifting-Ansatz und eine Technik zur Spektralformung von Quantisierungsfehlern eine Verbesserung der Approximation der ursprünglichen Transformation. Basierend auf diesen neuen Integer-Transformationen werden in dieser Arbeit neue Verfahren zur Audiocodierung vorgestellt. Die Verfahren umfassen verlustlose Audiocodierung, eine skalierbare verlustlose Erweiterung eines gehörangepassten Audiocoders und einen integrierten Ansatz zur fein skalierbaren gehörangepassten und verlustlosen Audiocodierung. Schließlich wird mit Hilfe der Integer-Transformationen ein neuer Ansatz zur unhörbaren Einbettung von Daten mit hohen Datenraten in unkomprimierte Audiosignale vorgestellt.In recent years audio coding has become a very popular field for research and applications. Especially perceptual audio coding schemes, such as MPEG-1 Layer-3 (MP3) and MPEG-2 Advanced Audio Coding (AAC), are widely used for efficient storage and transmission of music signals. Nevertheless, for professional applications, such as archiving and transmission in studio environments, lossless audio coding schemes are considered more appropriate. Traditionally, the technical approaches used in perceptual and lossless audio coding have been separate worlds. In perceptual audio coding, the use of filter banks, such as the lapped orthogonal transform "Modified Discrete Cosine Transform" (MDCT), has been the approach of choice being used by many state of the art coding schemes. On the other hand, lossless audio coding schemes mostly employ predictive coding of waveforms to remove redundancy. Only few attempts have been made so far to use transform coding for the purpose of lossless audio coding. This work presents a new approach of applying the lifting scheme to lapped transforms used in perceptual audio coding. This allows for an invertible integer-to-integer approximation of the original transform, e.g. the IntMDCT as an integer approximation of the MDCT. The same technique can also be applied to low-delay filter banks. A generalized, multi-dimensional lifting approach and a noise-shaping technique are introduced, allowing to further optimize the accuracy of the approximation to the original transform. Based on these new integer transforms, this work presents new audio coding schemes and applications. The audio coding applications cover lossless audio coding, scalable lossless enhancement of a perceptual audio coder and fine-grain scalable perceptual and lossless audio coding. Finally an approach to data hiding with high data rates in uncompressed audio signals based on integer transforms is described

Scalable and perceptual audio compression

This thesis deals with scalable perceptual audio compression. Two scalable perceptual solutions as well as a scalable to lossless solution are proposed and investigated. One of the scalable perceptual solutions is built around sinusoidal modelling of the audio signal whilst the other is built on a transform coding paradigm. The scalable coders are shown to scale both in a waveform matching manner as well as a psychoacoustic manner. In order to measure the psychoacoustic scalability of the systems investigated in this thesis, the similarity between the original signal\u27s psychoacoustic parameters and that of the synthesized signal are compared. The psychoacoustic parameters used are loudness, sharpness, tonahty and roughness. This analysis technique is a novel method used in this thesis and it allows an insight into the perceptual distortion that has been introduced by any coder analyzed in this manner

Experimental Investigation of Mode I Rock Fracture Toughness

Programa Oficial de Doutoramento en Enxeñaría Civil . 5011V01[Abstract] Mode I fracture toughness (KIC) is one of the most important parameters in rock fracture mechanics. KIC is an intrinsic material property that represents the ability of a material containing a pre-existing defect to resist tensile failure. The International Society for Rock Mechanics (ISRM) has proposed four suggested methods for determining KIC. However, these methods present some drawbacks. The main objective of this thesis is to develop a simple testing approach, called pseudo-compact tension (pCT) test, to measure KIC in rocks using cylindrical single edge-notched specimens loaded in pure tension. The study is based on the results of a large set of fracture toughness experiments performed with different rock types, sample sizes, and a range of notch length ratios. The KIC values derived with the pCT test are compared with those obtained with one of the suggested methods of the ISRM, the semi-circular bend (SCB) test. Some selected pCT and SCB tests were also complemented with the concurrent monitoring of the acoustic emission (AE) activity. With the obtained data, we compare and analyse both testing methods, the effects of specimen size, notch length and lithology, the mechanical evolution along the experiments and the significance of different AE parameters.[Resumen] La tenacidad de fractura en modo I (KIC) es uno de los parámetros más importantes en la mecánica de fractura aplicada a rocas. KIC es una propiedad intrínseca del material que representa su capacidad para resistir su rotura a tracción en la presencia de un defecto preexistente. La Sociedad Internacional para la Mecánica de Rocas (ISRM) ha sugerido cuatro métodos para determinar KIC, pero todos presentan algunos inconvenientes. El principal objetivo de esta tesis es desarrollar un método de ensayo simple, llamado ‘pseudo-compact tensión’ (pCT), para determinar KIC en rocas mediante muestras cilíndricas ensayadas bajo condiciones de tracción pura. El estudio se basa en los resultados de un número de ensayos llevados a cabo con distintos tipos de roca, tamaños de probeta y longitudes de entalla. Los valores de KIC obtenidos con el ensayo pCT se comparan con los obtenidos con el ensayo ‘semi-circular bend’ (SCB), uno de los métodos sugeridos por la ISRM. En algunos de estos ensayos también se registró la emisión acústica (AE). Con los datos obtenidos, comparamos y analizamos ambos métodos, los efectos del tamaño de probeta, longitud de entalla y litología, la evolución mecánica y la importancia de diferentes parámetros de AE durante los ensayos.[Resumo] A tenacidade de fractura en modo I (KIC) é un dos parámetros máis importantes na mecánica de fractura aplicada a rochas. KIC é unha propiedade intrínseca do material que representa a súa capacidade para resistir a súa rotura a tracción na presenza dun defecto preexistente. A Sociedade Internacional para a Mecánica de Rochas (ISRM) suxeriu catro métodos para determinar KIC, mais todos presentan algúns inconvenientes. O principal obxectivo desta tese é desenvolver un método de ensaio simple, chamado ‘pseudo-compact tensión’ (pCT), para determinar KIC en rocha mediante mostras cilíndricas ensaiadas baixo condiciones de tracción pura. O estudo baséase nos resultados dun número de ensaios levados a cabo con distintos tipos de rocha, tamaños de probeta e lonxitudes de entalla. Os valores de KIC obtidos co ensaio pCT compáranse cos obtidos co ensaio ‘semi-circular bend’ (SCB), un dos métodos suxeridos pola ISRM. Nalgúns destes ensaios tamén se rexistrou a emisión acústica (AE). Cos datos obtidos, comparamos e analizamos ambos métodos, os efectos do tamaño de probeta, lonxitude de entalla e litoloxía, a evolución mecánica e a importancia de diferentes parámetros de AE durante os ensaio

Optimization of Operation Sequencing in CAPP Using Hybrid Genetic Algorithm and Simulated Annealing Approach

In any CAPP system, one of the most important process planning functions is selection of the operations and corresponding machines in order to generate the optimal operation sequence. In this paper, the hybrid GA-SA algorithm is used to solve this combinatorial optimization NP (Non-deterministic Polynomial) problem. The network representation is adopted to describe operation and sequencing flexibility in process planning and the mathematical model for process planning is described with the objective of minimizing the production time. Experimental results show effectiveness of the hybrid algorithm that, in comparison with the GA and SA standalone algorithms, gives optimal operation sequence with lesser computational time and lesser number of iterations