Modeling And Implimentation Of Digital Distortion Audio Effect Algorithms

Cooperated with Eleca Electronics Co.Ltd, this project aims to design and implement an audio effects processing system based on DSP, which includes 17 kinds of effects such as delay, chorus, flanger, distortion, blues, reverberation, equalization and so on. The research of this paper focuses on the modeling and implementation of distortion type effects. Distortion effects are important parts of these 17 effects, including amplify, blues, dist, metal, and overdrive. They could be further divided into two classes linear distortion and nonlinear distortion, according to their characteristics. Among the distortion type effects, amplify is a kind of linear distortion, while blues, dist, metal and overdrive belong to another.As a theoretical basis to establish the mathematical model for audio effect, system modeling theory firstly is expatiated on, including the definition of system modeling, methodology of linear system's modelling, and methodology of nonlinear system's modeling. Secondly, the modeling of amplify effect is taken as an example for modeling of linear distortion effects using adaptive filter. Thirdly, the modeling of blues effect is taken as an example of nonlinear distortion effects. Besides, hard clipping and soft clipping are compared and analyzed. As to the modeling of blues effect, two kinds of methods are discussed. One is to establish the natural model of blues effect by theoretical analysis and experiments. While, the other obtains the model by approaching the input-output characteristic of the blues effect sample using BP Neuron Network. The reason is that the Neuron Network is able to approach any kind of nonlinear system.As the platform to run the audio effect algorithms, the implementation of this digital audio effects processing system is another emphasis of this paper. After analyzing the requirements of the whole system and the problem that should be paid attention to, a system solution based on Motorola DSP56362 is proposed. Then, details about hardware design and software design are fully discussed, including the implementation of distortion effect algorithms, the design of embedded task management kernel, the design of dual loading module, and the erasing and programming of flash memory by software programming. Moreover, joint system experiments are also carried out, along with the corresponding experimental results and analysis.In the end, a summary is proposed for the whole system's research. Some means to improve this system are also discussed, as well as the future research object.