DAFX: Digital Audio Effects, Second Edition

13.2 AM-DAFX

From the point of view of signal flow, a DAFX is a device that takes an un-processed input signal and outputs a processed signal. In most cases the user can control the signal-processing behaviour by manipulating a number of parameters through a graphical user interface. The aim of the user is to manipulate the signal-processing parameters in order to produce the desired transformation of the input signals. Figure 13.1 shows the standard implementation of a DAFX, where x(n) is the input source and y(n) is the output resulting from the signal processing.

Figure 13.1 Diagram of a DAFX and user.

In an automatic-mixing context we aim to aid or replace the task normally performed by the user. In order to achieve this, some important design objectives should be performed by the AM-DAFX:

1. The system should comply with all the technical constraints of a mixture, such as avoiding distortion and maintaining adequate dynamic range.

2. The design should simplify complex mixing tasks while performing at a standard similar to that of an expert user.

3. For sound-reinforcement applications the system must remain free of undesired acoustic feedback artefacts.

In the case of a system used for live performance mixing, the automatic system must avoid undesired acoustic feedback artefacts at all cost. For this reason several stability solutions have been developed, for example gain ...