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Audio Plugin Skeleton ​

A minimal plug-in with a processor and editor, ready to build as VST3, AU, or Standalone.

  • AudioProcessor and AudioProcessorEditor split
  • prepareToPlay and processBlock
  • CMake setup with juce_add_plugin

Source: examples/CMake/AudioPlugin on GitHub.

cpp
#pragma once

#include <juce_audio_processors/juce_audio_processors.h>

//==============================================================================
class AudioPluginAudioProcessor final : public juce::AudioProcessor
{
public:
    //==============================================================================
    AudioPluginAudioProcessor();
    ~AudioPluginAudioProcessor() override;

    //==============================================================================
    void prepareToPlay (double sampleRate, int samplesPerBlock) override;
    void releaseResources() override;

    bool isBusesLayoutSupported (const BusesLayout& layouts) const override;

    void processBlock (juce::AudioBuffer<float>&, juce::MidiBuffer&) override;
    using AudioProcessor::processBlock;

    //==============================================================================
    juce::AudioProcessorEditor* createEditor() override;
    bool hasEditor() const override;

    //==============================================================================
    const juce::String getName() const override;

    bool acceptsMidi() const override;
    bool producesMidi() const override;
    bool isMidiEffect() const override;
    double getTailLengthSeconds() const override;

    //==============================================================================
    int getNumPrograms() override;
    int getCurrentProgram() override;
    void setCurrentProgram (int index) override;
    const juce::String getProgramName (int index) override;
    void changeProgramName (int index, const juce::String& newName) override;

    //==============================================================================
    void getStateInformation (juce::MemoryBlock& destData) override;
    void setStateInformation (const void* data, int sizeInBytes) override;

private:
    //==============================================================================
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AudioPluginAudioProcessor)
};
cpp
#include "PluginProcessor.h"
#include "PluginEditor.h"

//==============================================================================
AudioPluginAudioProcessor::AudioPluginAudioProcessor()
     : AudioProcessor (BusesProperties()
                     #if ! JucePlugin_IsMidiEffect
                      #if ! JucePlugin_IsSynth
                       .withInput  ("Input",  juce::AudioChannelSet::stereo(), true)
                      #endif
                       .withOutput ("Output", juce::AudioChannelSet::stereo(), true)
                     #endif
                       )
{
}

AudioPluginAudioProcessor::~AudioPluginAudioProcessor()
{
}

//==============================================================================
const juce::String AudioPluginAudioProcessor::getName() const
{
    return JucePlugin_Name;
}

bool AudioPluginAudioProcessor::acceptsMidi() const
{
   #if JucePlugin_WantsMidiInput
    return true;
   #else
    return false;
   #endif
}

bool AudioPluginAudioProcessor::producesMidi() const
{
   #if JucePlugin_ProducesMidiOutput
    return true;
   #else
    return false;
   #endif
}

bool AudioPluginAudioProcessor::isMidiEffect() const
{
   #if JucePlugin_IsMidiEffect
    return true;
   #else
    return false;
   #endif
}

double AudioPluginAudioProcessor::getTailLengthSeconds() const
{
    return 0.0;
}

int AudioPluginAudioProcessor::getNumPrograms()
{
    return 1;   // NB: some hosts don't cope very well if you tell them there are 0 programs,
                // so this should be at least 1, even if you're not really implementing programs.
}

int AudioPluginAudioProcessor::getCurrentProgram()
{
    return 0;
}

void AudioPluginAudioProcessor::setCurrentProgram (int index)
{
    juce::ignoreUnused (index);
}

const juce::String AudioPluginAudioProcessor::getProgramName (int index)
{
    juce::ignoreUnused (index);
    return {};
}

void AudioPluginAudioProcessor::changeProgramName (int index, const juce::String& newName)
{
    juce::ignoreUnused (index, newName);
}

//==============================================================================
void AudioPluginAudioProcessor::prepareToPlay (double sampleRate, int samplesPerBlock)
{
    // Use this method as the place to do any pre-playback
    // initialisation that you need..
    juce::ignoreUnused (sampleRate, samplesPerBlock);
}

void AudioPluginAudioProcessor::releaseResources()
{
    // When playback stops, you can use this as an opportunity to free up any
    // spare memory, etc.
}

bool AudioPluginAudioProcessor::isBusesLayoutSupported (const BusesLayout& layouts) const
{
  #if JucePlugin_IsMidiEffect
    juce::ignoreUnused (layouts);
    return true;
  #else
    // This is the place where you check if the layout is supported.
    // In this template code we only support mono or stereo.
    // Some plugin hosts, such as certain GarageBand versions, will only
    // load plugins that support stereo bus layouts.
    if (layouts.getMainOutputChannelSet() != juce::AudioChannelSet::mono()
     && layouts.getMainOutputChannelSet() != juce::AudioChannelSet::stereo())
        return false;

    // This checks if the input layout matches the output layout
   #if ! JucePlugin_IsSynth
    if (layouts.getMainOutputChannelSet() != layouts.getMainInputChannelSet())
        return false;
   #endif

    return true;
  #endif
}

void AudioPluginAudioProcessor::processBlock (juce::AudioBuffer<float>& buffer,
                                              juce::MidiBuffer& midiMessages)
{
    juce::ignoreUnused (midiMessages);

    juce::ScopedNoDenormals noDenormals;
    auto totalNumInputChannels  = getTotalNumInputChannels();
    auto totalNumOutputChannels = getTotalNumOutputChannels();

    // In case we have more outputs than inputs, this code clears any output
    // channels that didn't contain input data, (because these aren't
    // guaranteed to be empty - they may contain garbage).
    // This is here to avoid people getting screaming feedback
    // when they first compile a plugin, but obviously you don't need to keep
    // this code if your algorithm always overwrites all the output channels.
    for (auto i = totalNumInputChannels; i < totalNumOutputChannels; ++i)
        buffer.clear (i, 0, buffer.getNumSamples());

    // This is the place where you'd normally do the guts of your plugin's
    // audio processing...
    // Make sure to reset the state if your inner loop is processing
    // the samples and the outer loop is handling the channels.
    // Alternatively, you can process the samples with the channels
    // interleaved by keeping the same state.
    for (int channel = 0; channel < totalNumInputChannels; ++channel)
    {
        auto* channelData = buffer.getWritePointer (channel);
        juce::ignoreUnused (channelData);
        // ..do something to the data...
    }
}

//==============================================================================
bool AudioPluginAudioProcessor::hasEditor() const
{
    return true; // (change this to false if you choose to not supply an editor)
}

juce::AudioProcessorEditor* AudioPluginAudioProcessor::createEditor()
{
    return new AudioPluginAudioProcessorEditor (*this);
}

//==============================================================================
void AudioPluginAudioProcessor::getStateInformation (juce::MemoryBlock& destData)
{
    // You should use this method to store your parameters in the memory block.
    // You could do that either as raw data, or use the XML or ValueTree classes
    // as intermediaries to make it easy to save and load complex data.
    juce::ignoreUnused (destData);
}

void AudioPluginAudioProcessor::setStateInformation (const void* data, int sizeInBytes)
{
    // You should use this method to restore your parameters from this memory block,
    // whose contents will have been created by the getStateInformation() call.
    juce::ignoreUnused (data, sizeInBytes);
}

//==============================================================================
// This creates new instances of the plugin..
juce::AudioProcessor* JUCE_CALLTYPE createPluginFilter()
{
    return new AudioPluginAudioProcessor();
}
cpp
#pragma once

#include "PluginProcessor.h"

//==============================================================================
class AudioPluginAudioProcessorEditor final : public juce::AudioProcessorEditor
{
public:
    explicit AudioPluginAudioProcessorEditor (AudioPluginAudioProcessor&);
    ~AudioPluginAudioProcessorEditor() override;

    //==============================================================================
    void paint (juce::Graphics&) override;
    void resized() override;

private:
    // This reference is provided as a quick way for your editor to
    // access the processor object that created it.
    AudioPluginAudioProcessor& processorRef;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AudioPluginAudioProcessorEditor)
};
cpp
#include "PluginProcessor.h"
#include "PluginEditor.h"

//==============================================================================
AudioPluginAudioProcessorEditor::AudioPluginAudioProcessorEditor (AudioPluginAudioProcessor& p)
    : AudioProcessorEditor (&p), processorRef (p)
{
    juce::ignoreUnused (processorRef);
    // Make sure that before the constructor has finished, you've set the
    // editor's size to whatever you need it to be.
    setSize (400, 300);
}

AudioPluginAudioProcessorEditor::~AudioPluginAudioProcessorEditor()
{
}

//==============================================================================
void AudioPluginAudioProcessorEditor::paint (juce::Graphics& g)
{
    // (Our component is opaque, so we must completely fill the background with a solid colour)
    g.fillAll (getLookAndFeel().findColour (juce::ResizableWindow::backgroundColourId));

    g.setColour (juce::Colours::white);
    g.setFont (15.0f);
    g.drawFittedText ("Hello World!", getLocalBounds(), juce::Justification::centred, 1);
}

void AudioPluginAudioProcessorEditor::resized()
{
    // This is generally where you'll want to lay out the positions of any
    // subcomponents in your editor..
}
cmake
# Example Audio Plugin CMakeLists.txt

# To get started on a new plugin, copy this entire folder (containing this file and C++ sources) to
# a convenient location, and then start making modifications.

# The first line of any CMake project should be a call to `cmake_minimum_required`, which checks
# that the installed CMake will be able to understand the following CMakeLists, and ensures that
# CMake's behaviour is compatible with the named version. This is a standard CMake command, so more
# information can be found in the CMake docs.

cmake_minimum_required(VERSION 3.22)

# The top-level CMakeLists.txt file for a project must contain a literal, direct call to the
# `project()` command. `project()` sets up some helpful variables that describe source/binary
# directories, and the current project version. This is a standard CMake command.

project(AUDIO_PLUGIN_EXAMPLE VERSION 0.0.1)

# If you've installed JUCE somehow (via a package manager, or directly using the CMake install
# target), you'll need to tell this project that it depends on the installed copy of JUCE. If you've
# included JUCE directly in your source tree (perhaps as a submodule), you'll need to tell CMake to
# include that subdirectory as part of the build.

# find_package(JUCE CONFIG REQUIRED)        # If you've installed JUCE to your system
# or
# add_subdirectory(JUCE)                    # If you've put JUCE in a subdirectory called JUCE

# If you are building a VST2, CMake needs to be told where to find the SDK on your
# system. This setup should be done before calling `juce_add_plugin`.

# juce_set_vst2_sdk_path(...)

# `juce_add_plugin` adds a static library target with the name passed as the first argument
# (AudioPluginExample here). This target is a normal CMake target, but has a lot of extra properties set
# up by default. As well as this shared code static library, this function adds targets for each of
# the formats specified by the FORMATS arguments. This function accepts many optional arguments.
# Check the readme at `docs/CMake API.md` in the JUCE repo for the full list.

juce_add_plugin(AudioPluginExample
    # VERSION ...                               # Set this if the plugin version is different to the project version
    # ICON_BIG ...                              # ICON_* arguments specify a path to an image file to use as an icon for the Standalone
    # ICON_SMALL ...
    # COMPANY_NAME ...                          # Specify the name of the plugin's author
    # IS_SYNTH TRUE/FALSE                       # Is this a synth or an effect?
    # NEEDS_MIDI_INPUT TRUE/FALSE               # Does the plugin need midi input?
    # NEEDS_MIDI_OUTPUT TRUE/FALSE              # Does the plugin need midi output?
    # IS_MIDI_EFFECT TRUE/FALSE                 # Is this plugin a MIDI effect?
    # EDITOR_WANTS_KEYBOARD_FOCUS TRUE/FALSE    # Does the editor need keyboard focus?
    # COPY_PLUGIN_AFTER_BUILD TRUE/FALSE        # Should the plugin be installed to a default location after building?
    PLUGIN_MANUFACTURER_CODE Juce               # A four-character manufacturer id with at least one upper-case character
    PLUGIN_CODE Dem0                            # A unique four-character plugin id with exactly one upper-case character
                                                # GarageBand 10.3 requires the first letter to be upper-case, and the remaining letters to be lower-case
    FORMATS AU VST3 Standalone                  # The formats to build. Other valid formats are: AAX Unity VST AU AUv3
    PRODUCT_NAME "Audio Plugin Example"         # The name of the final executable, which can differ from the target name
    NEEDS_WEB_BROWSER FALSE                     # Set to TRUE if you need to use webviews
    NEEDS_CURL FALSE)                           # Set to TRUE if you need to use curl

# `juce_generate_juce_header` will create a JuceHeader.h for a given target, which will be generated
# into your build tree. This should be included with `#include <JuceHeader.h>`. The include path for
# this header will be automatically added to the target. The main function of the JuceHeader is to
# include all your JUCE module headers; if you're happy to include module headers directly, you
# probably don't need to call this.

# juce_generate_juce_header(AudioPluginExample)

# `target_sources` adds source files to a target. We pass the target that needs the sources as the
# first argument, then a visibility parameter for the sources which should normally be PRIVATE.
# Finally, we supply a list of source files that will be built into the target. This is a standard
# CMake command.

target_sources(AudioPluginExample
    PRIVATE
        PluginEditor.cpp
        PluginProcessor.cpp)

# `target_compile_definitions` adds some preprocessor definitions to our target. In a Projucer
# project, these might be passed in the 'Preprocessor Definitions' field. JUCE modules also make use
# of compile definitions to switch certain features on/off, so if there's a particular feature you
# need that's not on by default, check the module header for the correct flag to set here. These
# definitions will be visible both to your code, and also the JUCE module code, so for new
# definitions, pick unique names that are unlikely to collide! This is a standard CMake command.

target_compile_definitions(AudioPluginExample
    PUBLIC
        # JUCE_WEB_BROWSER and JUCE_USE_CURL would be on by default, but you might not need them.
        JUCE_WEB_BROWSER=0  # If you remove this, add `NEEDS_WEB_BROWSER TRUE` to the `juce_add_plugin` call
        JUCE_USE_CURL=0     # If you remove this, add `NEEDS_CURL TRUE` to the `juce_add_plugin` call
        JUCE_VST3_CAN_REPLACE_VST2=0)

# If your target needs extra binary assets, you can add them here. The first argument is the name of
# a new static library target that will include all the binary resources. There is an optional
# `NAMESPACE` argument that can specify the namespace of the generated binary data class. Finally,
# the SOURCES argument should be followed by a list of source files that should be built into the
# static library. These source files can be of any kind (wav data, images, fonts, icons etc.).
# Conversion to binary-data will happen when your target is built.

# juce_add_binary_data(AudioPluginData SOURCES ...)

# `target_link_libraries` links libraries and JUCE modules to other libraries or executables. Here,
# we're linking our executable target to the `juce::juce_audio_utils` module. Inter-module
# dependencies are resolved automatically, so `juce_core`, `juce_events` and so on will also be
# linked automatically. If we'd generated a binary data target above, we would need to link to it
# here too. This is a standard CMake command.

target_link_libraries(AudioPluginExample
    PRIVATE
        # AudioPluginData           # If we'd created a binary data target, we'd link to it here
        juce::juce_audio_utils
    PUBLIC
        juce::juce_recommended_config_flags
        juce::juce_recommended_lto_flags
        juce::juce_recommended_warning_flags)

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