Welcome to the official repository for VIOLA, a framework designed for the automatic generation of virtual analog audio plug-ins using Wave Digital Filters (WDFs). This repository accompanies our paper:
"VIOLA: A Framework for the Automatic Generation of Virtual Analog Audio Plug-ins based on WDFs," authored by R. Giampiccolo, S. Ravasi, and A. Bernardini, and submitted to the special issue "The Sound of Digital Audio Effects" of the Journal of the Audio Engineering Society.

VIOLA simplifies the creation of Virtual Analog audio plug-ins, exploiting the modularity and efficiency of WDFs. Users just have to draw a circuit in LTspice and that's it: VIOLA will generate the audio plug-in making use of the MATLAB Audio Toolbox for the automatic design of the graphic user interface and the conversion of code to C++.

• Automatic Plug-in Creation: Simplify the creation of virtual analog plug-ins from your circuit designs.
• Custom LTspice Library: Design circuits easily with a tailored library of components.
• Pre-Built Examples: Start experimenting with ready-to-use examples.
• Audio Examples: Explore audio demonstrations to hear VIOLA's capabilities.

• Windows OS: The codebase is fully functional and available for use.
• MacOS Support: The codebase is fully functional and available for use.

• Matlab R2024a or Later: The tool has been developed with version R2024a.
• Matlab Audio Toolbox: Fundamental to access "audioPlugin" class and realted subclasses.
• Matlab Coder: Automatic C++ code generation and plugin deployment.
• Supported C++ Coder: More information about can be found at Supported compilers.
• MacOS Users: update and/or install Xcode v16. Then, run sudo xcode-select -switch <path-to-xcode.app> in your terminal. In Matlab's command window run:

  mex -setup C++
  mex -setup C
  

Discover the power of VIOLA by listening to audio examples on our GitHub page.

Design and simulate circuits in LTspice using the custom component library provided:

• Find the library files in the ltspice_custom_components/ directory.
• Copy all the files inside the directory of your .asc file. The circuit symbols of custom components are in the file ltspice_custom_components/CustomComponents.asc.
• Explore example circuits in the windows/Data/Input/Netlist/ directory.
• Test the pre-built audio plug-ins of the windows/Results/ directory in your DAWs.

To draw compatible schematics on LTspice for VIOLA, some rules must be respected:

• The input signal can be specified as a voltage/current source using the name "Vin" or "Iin".
• Only one input signal can be provided (all the generated plugins are mono).
• Eventual DC voltage/current source name can be left unaltered (V1, V2, etc.).
• Do not assign the same name to different components (e.g., having two resistors named "R1" will give an error).
• Do not rename the nodes (leave the SPICE labeling: N001, N002, etc.). To specify the output node in MATLAB main write down the right node from LTspice and specify it as a string (e.g., "N005").
• Custom element names must be declared as follows: D (diodes), Dser (diode series), Dap (antiparallel diodes), Plin (lin potentiometers), Plog (log potentiometers), Pilog (inv-log potentiometers), OA (ideal opamps). Then, a number has to be added after each label to distinguish the different components.
• Specify diode parameters in the following order: Is, eta, Vth, Rs, Rp (e.g., Is=4.352n eta=1.905 Vth=25.8563m Rs=1m Rp=1Meg).
• Series and antiparallel combinations on diodes also require the addition of the parameter n (to account for the number of diodes in series).
• Assign progressive numbers to potentiometers, even though they differ in type (e.g., "Plin1", "Plog2", "Plin3", etc.).
• Specify potentiometer parameters in the right order: Rp, x (e.g., Rp=100k x=0.75).

• Additional Examples: New circuit designs will be added.
• Efficiency Enhancements: Codebase will be refactored and improved.
• Additional Components: New circuit components will be added.

We welcome contributions! Feel free to:

• Report issues.
• Request features.
• Submit pull requests.

For inquiries or feedback, reach out via email:
riccardo.giampiccolo@polimi.it stefanoravasi98@gmail.com

This project is licensed under the GPL-3.0 License. See the LICENSE file for more details.