Subtractive synthesis is a popular method used in audio synthesis to create and manipulate sounds. It involves subtracting harmonic content from an initial rich waveform to shape and sculpt the desired sound. In this blog post, we will explore how to implement subtractive synthesis in C++.

Understanding subtractive synthesis

Subtractive synthesis typically involves three main components: an oscillator, a filter, and an amplifier. The oscillator generates the initial waveform, the filter shapes the harmonic content, and the amplifier controls the volume.

Implementing subtractive synthesis in C++

To get started, we need to set up a C++ project and include the necessary libraries for audio processing. We will be using the RtAudio library for audio input/output and the C++ Standard Library for basic arithmetic operations.

First, let’s create a class called SubtractiveSynth that represents our subtractive synthesizer:

#include <iostream>
#include <cmath>
#include <rtaudio/RtAudio.h>

class SubtractiveSynth {
public:
    SubtractiveSynth();
    ~SubtractiveSynth();

    void generateSound();
    void playSound();
    void stopSound();

private:
    RtAudio audio;
    float frequency;
    float amplitude;
    float phase;

    static int audioCallback(void* outputBuffer, void* inputBuffer,
                             unsigned int nBufferFrames,
                             double streamTime, RtAudioStreamStatus status, void* userData);
};

In the SubtractiveSynth class, we have a constructor, destructor, and three main methods for generating, playing, and stopping the sound. We also declare a few variables for frequency, amplitude, and phase of the audio.

Next, let’s implement the methods:

SubtractiveSynth::SubtractiveSynth() {
    // Initialize the audio system
    RtAudio::StreamParameters params;
    params.deviceId = audio.getDefaultOutputDevice();
    params.nChannels = 1; // Mono output
    params.firstChannel = 0;

    RtAudio::StreamOptions options;
    unsigned int bufferFrames = 512; // Adjustable buffer size

    audio.openStream(&params, nullptr, RTAUDIO_FLOAT32, SAMPLE_RATE, &bufferFrames,
                     &SubtractiveSynth::audioCallback, this, &options);
    audio.startStream();
}

SubtractiveSynth::~SubtractiveSynth() {
    if (audio.isStreamRunning())
        audio.stopStream();
    audio.closeStream();
}

void SubtractiveSynth::generateSound() {
    // Generate audio samples and store in a buffer
}

void SubtractiveSynth::playSound() {
    // Play the generated sound
}

void SubtractiveSynth::stopSound() {
    // Stop the sound playback
}

int SubtractiveSynth::audioCallback(void* outputBuffer, void* inputBuffer,
                                   unsigned int nBufferFrames,
                                   double streamTime, RtAudioStreamStatus status, void* userData) {
    // Audio callback function implementation
    return 0;
}

In the constructor of the SubtractiveSynth class, we initialize the audio system and open an audio stream for output using the RtAudio library. We also define an audio callback function that will be called whenever the audio system needs more audio data.

The generateSound() method will be responsible for generating the audio samples according to the subtractive synthesis algorithm, while the playSound() and stopSound() methods will handle playing and stopping the sound playback, respectively.

Conclusion

Subtractive synthesis is a powerful technique for audio synthesis, allowing you to shape and manipulate sounds to create unique and interesting audio. By implementing subtractive synthesis in C++ using the RtAudio library, you can unlock a world of possibilities for sound design and music production.

#programming #audio #synthesis #subtractive #C++