Audio effects library for Digital Signal Processor

Abstract

Digital Signal Processing (DSP) is continuously evolving and is used in various applications including audio. DSP is heavily used in the music and film industry. There are a lot of offline algorithms and applications to process audio DSP but algorithms that perform DSP in real-time audio applications are more limited. These are used by live audio engineers and live musicians to enhance their instrument’s sound. Such digital effects are usually computationally expensive if performed on a generic low-performance processor. Thus executing DSP code on a Digital Signal Processor is much more efficient. However today's low-performance processors are powerful enough for basic audio processing, but using a DSP device could improve quality for example by using more coefficients, or running more effects at the same time. The aim of this project was to identify and implement a number of audio effects as an audio effects library that performs real-time DSP on audio signals. These effects include: gain, reverb, echo, chorus, tremolo, equalisation and pitch change. Moreover, a demonstration application that makes use of this audio effects library to be used in live audio applications was developed. The code had to be optimised as much as possible for an efficient execution on a Digital Signal Processing Board. The library was used successfully in an embedded system with an ARM Cortex-M4 processor. Tests confirm proper operation of the digital audio effects. Audio was played back to ensure there were no audible artefacts.