Developing Audio Plugins with JUCE and Visual Studio Code

· 724 words · 4 minute read

Developing audio plugins can be a daunting at first. Except for knowledge of C++, one has to have knowledge of digital signal processing, GUI development. However, the first obstacle is getting to know a good plugin development framework. JUCE is pretty much the industry standard in this regard. Unfortunately, the JUCE quickstart is not very beginner friendly. It will start to explain the Projucer, a custom system that creates XCode and Visual Studio build files. Although good IDEs, many people prefer VSCode or CLion. Although not clear from the website, these are also supported via CMake. CMake markets itself as the de-facto standard for building C++ code and chances are you’ve come across it while browsing open source C++ projects.

In 2020, the JUCE team added support for CMake which can be used instead of the Projucer. To use CMake, you have to create a CMakeLists.txt file in your projects root directory. An example of such file specific to JUCE is given in the JUCE Github’s examples directory.

In this tutorial, I’ll be using VS Code on Mac with the C++ and CMake extensions.

Setting up the directory 🔗

Create your project folder. I’ll call mine example-plugin. Then clone the JUCE repository in there and copy the files in JUCE/examples/CMake/AudioPlugin to the example-plugin folder. Your directory structure should look like this:

example-plugin/
├── JUCE/
├── CMakeLists.txt
├── PluginEditor.cpp
├── PluginEditor.h
├── PluginProcessor.cpp
└── PluginProcessor.h

Setting up VS Code 🔗

Open the example-plugin folder in VS Code and install the C++ and Cmake plugins.

Now configure CMake by pressing Ctrl+Shift+p and typing CMake: configure. After pressing enter you will have to select a compiler and a build target. You can select DEBUG for now. If you press enter now, you will be greeted by the following error message:

CMake Error at CMakeLists.txt:40 (juce_add_plugin):
  Unknown CMake command "juce_add_plugin".

This is because we did not specify the location of the JUCE directory. Since it is simply in the project directory, we can uncomment the line that says add_subdirectory(JUCE) in CMakeLists.txt. After doing this, the error should go away.

Build the audio plugin 🔗

Now everything is set up, the last step is building the audio plugin. This can be done using the CMake build command. To invoke this, press Ctrl+Shift+p, type CMake: build target, and then select All. An executable and a vst3 plugin will be made in the build directory. You will have to go through some subdirectories to find it. The directory names depend on the compiler chosen, but my vst3 plugin was located in

build\AudioPluginExample_artefacts\Debug\VST3\Audio Plugin Example.vst3\Contents\x86_64-win

Automatically testing your plugin 🔗

To test your code you can use the Juce Plugin Host. This is a simple plugin that allows you to quickly load your plugin without the need to load a full DAW. Building it with CMake is relatively straightforward. Enter the JUCE folder and run the following commands.

cmake -B build
cmake -B build -DJUCE_BUILD_EXTRAS=ON
cmake --build build --target AudioPluginHost

Notice that we also include the extras which contains the AudioPluginHost. We first need to call cmake without the extras though, otherwise it will complain about juceaide not being found.

After this, we want to setup VS Code to automatically launch the plugin host when the plugin is built. To accomplish this, we need to add a launch configuration. Let’s also add a task to build the plugin before launching. Create a launch.json file in the .vscode folder and add the following:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Launch AudioPluginHost",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/JUCE/build/extras/AudioPluginHost/AudioPluginHost_artefacts/AudioPluginHost.app/Contents/MacOS/AudioPluginHost",
            "cwd": "${workspaceFolder}",
            "MIMode": "lldb",
            "preLaunchTask": "CMake: build"
        }
    ]
}

Now upon pressing F5, the plugin will be compiled and the plugin host will be launched. In the plugin host you can load the plugin from the build/AudioPluginExample_artefacts/ directory. Play around in the plugin host and once you have a setup that you like, you can save the PluginHost status in a .filtergraph file that will automatically be used when relaunching the plugin host.

Next steps 🔗

Now you have a basic setup, you might want to flesh it out with some extra features. What about testing your code, using all your cores. In the blog post by Melatonin.dev, more advanced CMake features are explained.

Also check out the PampleJUCE audio plugin template. It contains several very useful features including the automatic creation of installers for Windows/Mac using Github actions.

JUCE audio C++