An Evaluation Of Speech Coding Algorithms

Speech coding is a highly mature branch of signal processing deployed in products such as cellular phones, communication devices, and more recently, voice over internet protocol This book collects many of the techniques used in speech coding and presents them in an accessible fashion Emphasizes the foundation and evolution of standardized speech coders, covering standards from 1984 to the present The theory behind the applications is thoroughly analyzed and proved

Speech coding is a highly mature branch of signal processing deployed in products such as cellular phones, communication devices, and more recently, voice over internet protocol This book collects many of the techniques used in speech coding and presents them in an accessible fashion Emphasizes the foundation and evolution of standardized speech coders, covering standards from 1984 to the present The theory behind the applications is thoroughly analyzed and proved

From the early pulse code modulation-based coders to some of the recent multi-rate wideband speech coding standards, the area of speech coding made several significant strides with an objective to attain high quality of speech at the lowest possible bit rate. This book presents some of the recent advances in linear prediction (LP)-based speech analysis that employ perceptual models for narrow- and wide-band speech coding. The LP analysis-synthesis framework has been successful for speech coding because it fits well the source-system paradigm for speech synthesis. Limitations associated with the conventional LP have been studied extensively, and several extensions to LP-based analysis-synthesis have been proposed, e.g., the discrete all-pole modeling, the perceptual LP, the warped LP, the LP with modified filter structures, the IIR-based pure LP, all-pole modeling using the weighted-sum of LSP polynomials, the LP for low frequency emphasis, and the cascade-form LP. These extensions can be classified as algorithms that either attempt to improve the LP spectral envelope fitting performance or embed perceptual models in the LP. The first half of the book reviews some of the recent developments in predictive modeling of speech with the help of MatlabTM Simulation examples. Advantages of integrating perceptual models in low bit rate speech coding depend on the accuracy of these models to mimic the human performance and, more importantly, on the achievable "coding gains" and "computational overhead" associated with these physiological models. Methods that exploit the masking properties of the human ear in speech coding standards, even today, are largely based on concepts introduced by Schroeder and Atal in 1979. For example, a simple approach employed in speech coding standards is to use a perceptual weighting filter to shape the quantization noise according to the masking properties of the human ear. The second half of the book reviews some of the recent developments in perceptual modeling of speech (e.g., masking threshold, psychoacoustic models, auditory excitation pattern, and loudness) with the help of MatlabTM simulations. Supplementary material including MatlabTM programs and simulation examples presented in this book can also be accessed here. Table of Contents: Introduction / Predictive Modeling of Speech / Perceptual Modeling of Speech

After alm ost three scores of years of basic and applied research, the field of speech processing is, at present, undergoing a rapid growth in terms of both performance and applications and this is fueHed by the advances being made in the areas of microelectronics, computation and algorithm design.Speech processing relates to three aspects of voice communications: -Speech Coding and transmission which is mainly concerned with man-to man voice communication. -Speech Synthesis which deals with machine-to-man communication. -Speech Recognition which is related to man-to-machine communication. Widespread application and use of low-bit rate voice codec.>, synthesizers and recognizers which are all speech processing products requires ideaHy internationally accepted quality assessment and evaluation methods as weH as speech processing standards so that they may be interconnected and used independently of their designers and manufacturers without costly interfaces. This book presents, in a tutorial manner, both fundamental and applied aspects of the above topics which have been prepared by weH-known specialists in their respective areas. The book is based on lectures which were sponsored by AGARD/NATO and delivered by the authors, in several NATO countries, to audiences consisting mainly of academic and industrial R&D engineers and physicists as weH as civil and military C3I systems planners and designers.

A Practical Handbook of Speech Coders offers in-depth treatment of the basics of speech coding plus the innovations to the basic methods that make the coders useful and efficient. It describes the fundamentals of auditory information processing and how they relate to speech coding, and shows readers how to evaluate the strengths and weaknesses of all publicly available codes and choose the right one. It explains how to measure the quality of speech coders with objective, subjective, and perceptual measures. The book also shows engineers how to tailor existing speech coders and provides the building blocks to create new coders.

The demand for digital speech coding algorithms grows every day, fueled by applications such as streaming speech over the Internet, Internet telephone, digital cellular telephony, wireless teleconferencing, and various multimedia applications. Until now, most of the books available on audio coding have been collections of individually authored papers. Others have discussed the fundamental coders, but neglected many of the innovations currently in use. Unlike these books, A Practical Handbook of Speech Coders offers in-depth treatment of the basics of speech coding plus the innovations to the basic methods that make the coders useful and efficient. The authors designed this work for engineers, scientists, and manager who need to understand the emerging speech coding techniques and telecommunication standards. However, it will prove useful to people at all levels of speech coder experience: If you want to simply download the code for an existing algorithm, this book helps you evaluate the strengths and weaknesses of all publicly available codes and choose the right one, then points you to the Internet location where the code is available for download. For experts who want to improve on existing coders, this book provides the parameters of current coders and the techniques to improve upon them. You can download an existing algorithm or code it using the algorithmic descriptions in the book, make your innovations, and then test the code with the procedures given. If you want to become an expert and have some basic knowledge of digital signal processing, you can learn the innovative steps taken by the inventor of each coder, explore the rigorous research techniques needed to develop your own coder, and become proficient in existing vocoder technology.

You'll find complete coverage of the state-of-the-field, including pulse code modulators... adaptive pulse code modulators... adaptive differential pulse code modulation... adaptive predictive coders... linear predictive coders... code excited linear predictive coders... multipulse excited linear predictive coders... subband coders... transform coders, and much more.

It is becoming increasingly apparent that all forms of communication-including voice-will be transmitted through packet-switched networks based on the Internet Protocol (IP). Therefore, the design of modern devices that rely on speech interfaces, such as cell phones and PDAs, requires a complete and up-to-date understanding of the basics of speech