Applications of Digital Signal Processing to Audio and Acoustics (The Springer International Series in Engineering and Computer Science)
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Karlheinz Brandenburg and Mark Kahrs With the advent of multimedia, digital signal processing (DSP) of sound has emerged from the shadow of bandwidth limited speech processing. Today, the main appli cations of audio DSP are high quality audio coding and the digital generation and manipulation of music signals. They share common research topics including percep tual measurement techniques and analysis/synthesis methods. Smaller but nonetheless very important topics are hearing aids using signal processing technology and hardware architectures for digital signal processing of audio. In all these areas the last decade has seen a significant amount of application oriented research. The topics covered here coincide with the topics covered in the biannual work shop on “Applications of Signal Processing to Audio and Acoustics”. This event is sponsored by the IEEE Signal Processing Society (Technical Committee on Audio and Electroacoustics) and takes place at Mohonk Mountain House in New Paltz, New York. A short overview of each chapter will illustrate the wide variety of technical material presented in the chapters of this book. John Beerends: Perceptual Measurement Techniques. The advent of perceptual measurement techniques is a byproduct of the advent of digital coding for both speech and high quality audio signals. Traditional measurement schemes are bad estimates for the subjective quality after digital coding/decoding. Listening tests are subject to sta tistical uncertainties and the basic question of repeatability in a different environment.
Frequency-domain techniques 302 7.6 Discussion 303 7.6.1 Generic problems associated with time or pitch scaling 303 7.6.2 Time-domain vs frequency-domain techniques 308 8 Wavetable Sampling Synthesis 311 Dana C. Massie 8.1 Background and introduction 311 8.1.1 Transition to Digital 312 8.1.2 Flourishing of Digital Synthesis Methods 313 8.1.3 Metrics: The Sampling - Synthesis Continuum 314 8.1.4 Sampling vs. Synthesis 315 8.2 Wavetable Sampling Synthesis 318 8.2.1
the PAQM 18 1.8 Relation between MOS and PAQM, ISO/MPEG 1990 database 19 1.9 Relation between MOS and PAQM, ISO/MPEG 1991 database 21 1.10 Relation between MOS and PAQM, ITU-R 1993 database 22 1.11 Relation between MOS and PAQM, ETSI GSM full rate database 23 1.12 Relation between MOS and PAQM, ETSI GSM half rate database 24 1.13 Basic approach used in the development of PAQM C 25 1.14 Relation between MOS and PAQM 28 C , ISO/MPEG 1991 database 1.15 Relation between MOS
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Error resilience: Depending on the architecture of the bitstream, perceptual coders are more or less susceptible to single or burst errors on the transmission channel. This can be overcome by application of error-correction codes, but with more or less cost in terms of decoder complexity and/or decoding delay. Source coding versus perceptual coding. In speech, video and audio coding the original data are analog values which have been converted into the digital domain using sampling and
most analogue disc recording methods. For example, a poor quality 78 rpm record might typically have around 2,000 clicks per second of recorded material, with durations ranging from less than 20 µ s up to 4ms in extreme cases. See figure 4.1 for a typical example of a recorded music waveform degraded by localized clicks. In most examples at least 90% of samples remain undegraded, so it is reasonable to hope that a convincing restoration can be achieved. There are many mechanisms by which