Audio App

A simple audio application built on AudioAppComponent.

• AudioAppComponent
• Shared AudioDeviceManager
• prepareToPlay and getNextAudioBlock

Source: examples/Audio/AudioAppDemo.h on GitHub.

AudioAppDemo.h

/*******************************************************************************
 The block below describes the properties of this PIP. A PIP is a short snippet
 of code that can be read by the Projucer and used to generate a JUCE project.

 BEGIN_JUCE_PIP_METADATA

 name:             AudioAppDemo
 version:          1.0.0
 vendor:           JUCE
 website:          http://juce.com
 description:      Simple audio application.

 dependencies:     juce_audio_basics, juce_audio_devices, juce_audio_formats,
                   juce_audio_processors, juce_audio_utils, juce_core,
                   juce_data_structures, juce_events, juce_graphics,
                   juce_gui_basics, juce_gui_extra, juce_audio_processors_headless
 exporters:        xcode_mac, vs2022, vs2026, linux_make, androidstudio,
                   xcode_iphone

 moduleFlags:      JUCE_STRICT_REFCOUNTEDPOINTER=1

 type:             Component
 mainClass:        AudioAppDemo

 useLocalCopy:     1

 END_JUCE_PIP_METADATA

*******************************************************************************/

#pragma once


//==============================================================================
class AudioAppDemo final : public AudioAppComponent
{
public:
    //==============================================================================
    AudioAppDemo()
       #ifdef JUCE_DEMO_RUNNER
        : AudioAppComponent (getSharedAudioDeviceManager (0, 2))
       #endif
    {
        setAudioChannels (0, 2);

        setSize (800, 600);
    }

    ~AudioAppDemo() override
    {
        shutdownAudio();
    }

    //==============================================================================
    void prepareToPlay (int samplesPerBlockExpected, double newSampleRate) override
    {
        sampleRate = newSampleRate;
        expectedSamplesPerBlock = samplesPerBlockExpected;
    }

    /*  This method generates the actual audio samples.
        In this example the buffer is filled with a sine wave whose frequency and
        amplitude are controlled by the mouse position.
     */
    void getNextAudioBlock (const AudioSourceChannelInfo& bufferToFill) override
    {
        bufferToFill.clearActiveBufferRegion();
        auto originalPhase = phase;

        for (auto chan = 0; chan < bufferToFill.buffer->getNumChannels(); ++chan)
        {
            phase = originalPhase;

            auto* channelData = bufferToFill.buffer->getWritePointer (chan, bufferToFill.startSample);

            for (auto i = 0; i < bufferToFill.numSamples ; ++i)
            {
                channelData[i] = amplitude * std::sin (phase);

                // increment the phase step for the next sample
                phase = std::fmod (phase + phaseDelta, MathConstants<float>::twoPi);
            }
        }
    }

    void releaseResources() override
    {
        // This gets automatically called when audio device parameters change
        // or device is restarted.
    }


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

        auto centreY = (float) getHeight() / 2.0f;
        auto radius = amplitude * 200.0f;

        if (radius >= 0.0f)
        {
            // Draw an ellipse based on the mouse position and audio volume
            g.setColour (Colours::lightgreen);

            g.fillEllipse (jmax (0.0f, lastMousePosition.x) - radius / 2.0f,
                           jmax (0.0f, lastMousePosition.y) - radius / 2.0f,
                           radius, radius);
        }

        // Draw a representative sine wave.
        Path wavePath;
        wavePath.startNewSubPath (0, centreY);

        for (auto x = 1.0f; x < (float) getWidth(); ++x)
            wavePath.lineTo (x, centreY + amplitude * (float) getHeight() * 2.0f
                                            * std::sin (x * frequency * 0.0001f));

        g.setColour (getLookAndFeel().findColour (Slider::thumbColourId));
        g.strokePath (wavePath, PathStrokeType (2.0f));
    }

    // Mouse handling..
    void mouseDown (const MouseEvent& e) override
    {
        mouseDrag (e);
    }

    void mouseDrag (const MouseEvent& e) override
    {
        lastMousePosition = e.position;

        frequency = (float) (getHeight() - e.y) * 10.0f;
        amplitude = jmin (0.9f, 0.2f * e.position.x / (float) getWidth());

        phaseDelta = (float) (MathConstants<double>::twoPi * frequency / sampleRate);

        repaint();
    }

    void mouseUp (const MouseEvent&) override
    {
        amplitude = 0.0f;
        repaint();
    }

    void resized() override
    {
        // This is called when the component is resized.
        // If you add any child components, this is where you should
        // update their positions.
    }


private:
    //==============================================================================
    float phase       = 0.0f;
    float phaseDelta  = 0.0f;
    float frequency   = 5000.0f;
    float amplitude   = 0.2f;

    double sampleRate = 0.0;
    int expectedSamplesPerBlock = 0;
    Point<float> lastMousePosition;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AudioAppDemo)
};