Ebook: DAFX: Digital Audio Effects

Second edition. — John Wiley, 2011. — 614 p.DAFX is a synonym for digital audio effects. It is also the name for a European research project for co-operation and scientific transfer, namely EU-COST-G6 Digital Audio Effects (1997–2001). It was initiated by Daniel Arfib (CNRS, Marseille). In the past couple of years we have had four EU-sponsored international workshops/conferences on DAFX, namely, in Barcelona (DAFX-98), Trondheim (DAFX-99), Verona (DAFX-00) and Limerick (DAFX-01). A variety of DAFX topics have been presented by international participants at these conferences. The papers can be found on the corresponding web sites.
Chapter 1 gives an introduction to digital signal processing and shows software implementations with the MATLAB programming tool. Chapter 2 discusses digital filters for shaping the audio spectrum and focuses on the main building blocks for this application. Chapter 3 introduces basic structures for delays and delay-based audio effects. In Chapter 4 modulators and demodulators are introduced and their applications to digital audio effects are demonstrated. The topic of nonlinear processing is the focus of Chapter 5_. First, we discuss fundamentals of dynamics processing such as limiters, compressors/expanders and noise gates, and then we introduce the basics of nonlinear processors for valve simulation, distortion, harmonic generators and exciters. Chapter 6 covers the wide field of spatial effects starting with basic effects, 3D for headphones and loudspeakers, reverberation and spatial enhancements. Chapter 7 deals with time-segment processing and introduces techniques for variable speed replay, time stretching, pitch shifting, shuffling and granulation. In Chapter 8 we extend the time-domain processing of Chapters 2–7_. We introduce the fundamental techniques for time-frequency processing, demonstrate several implementation schemes and illustrate the variety of effects possible in the 2D time-frequency domain. Chapter 9 covers the field of source-filter processing, where the audio signal is modeled as a source signal and a filter. We introduce three techniques for source-filter separation and show source-filter transformations leading to audio effects such as cross-synthesis, formant changing, spectral interpolation and pitch shifting with formant preservation. The end of this chapter covers feature extraction techniques. Chapter 10 deals with spectral processing, where the audio signal is represented by spectral models such as sinusoids plus a residual signal. Techniques for analysis, higher-level feature analysis and synthesis are introduced, and a variety of new audio effects based on these spectral models are discussed. Effect applications range from pitch transposition, vibrato, spectral shape shift and gender change to harmonizer and morphing effects. Chapter 11 deals with fundamental principles of time and frequency warping techniques for deforming the time and/or the frequency axis. Applications of these techniques are presented for pitch-shifting inharmonic sounds, the inharmonizer, extraction of excitation signals, morphing and classical effects. Chapter 12 deals with the control of effect processors ranging from general control techniques to control based on sound features and gestural interfaces. Finally, Chapter 13 illustrates new challenges of bitstream signal representations, shows the fundamental basics and introduces filtering concepts for bitstream signal processing. MATLAB implementations in several chapters of the book illustrate software implementations of DAFX algorithms. The MATLAB files can be found on the web site http://www.dafx.de.Introduction
Filters and delays
Modulators and demodulators
Nonlinear processing
Spatial effects
Time-segment processing
Time-frequency processing
Source-filter processing
Adaptive digital audio effects
Spectral processing
Time and frequency-warping musical signals
Virtual analog effects
Automatic mixing
Sound source separation