Introduction

Audio effects play an important role in enhancing the quality and creativity of audio productions. One popular type of audio effect is the vocoder, which is commonly used in music production, voice modification, and sound design. In this blog post, we will explore how to implement audio effects using vocoders in C++.

What is a vocoder?

A vocoder is an audio processing technique that combines the characteristics of the human voice (or any other audio source) with a carrier signal, typically a musical instrument or synthesizer sound. The result is a unique and distinctive sound that can be used to create robotic voices, harmonies, and other creative effects.

Implementing a simple vocoder

To implement a basic vocoder in C++, we will need to do the following:

1. Load the audio samples of the voice and carrier signals.
2. Analyze the frequency content of the voice signal using a Fast Fourier Transform (FFT).
3. Extract the pitch and spectral envelope information from the voice signal.
4. Apply the spectral envelope to the carrier signal.
5. Synthesize the modified carrier signal.

Here is an example of how to implement a simple vocoder using the Essentia C++ library:

#include <essentia/algorithmfactory.h>
#include <essentia/essentiamath.h>

int main() {
    // Load voice and carrier audio samples
    std::vector<float> voiceSamples = loadAudioSamples("voice.wav");
    std::vector<float> carrierSamples = loadAudioSamples("carrier.wav");

    // Create an FFT object
    essentia::algorithm::FFT fft;

    // Perform the FFT on the voice signal
    std::vector<float> voiceSpectrum;
    fft.forward(voiceSamples, voiceSpectrum);

    // Extract pitch and spectral envelope information
    essentia::algorithm::PitchYinFFT pitchExtractor;
    float pitch = pitchExtractor(voiceSpectrum);

    essentia::algorithm::Spectrum spectralEnvelope;
    std::vector<float> envelope;
    fft.inverse(spectralEnvelope.apply(voiceSpectrum), envelope);

    // Apply the spectral envelope to the carrier signal
    std::vector<float> modifiedCarrierSamples;
    for (size_t i = 0; i < carrierSamples.size(); i++) {
        modifiedCarrierSamples[i] = carrierSamples[i] * envelope[i];
    }

    // Synthesize the modified carrier signal
    std::vector<float> outputSamples = synthesis(modifiedCarrierSamples, pitch);

    // Save the output audio samples
    saveAudioSamples(outputSamples, "output.wav");

    return 0;
}

Conclusion

Implementing audio effects using vocoders in C++ can add a new dimension to your audio productions. By analyzing and modifying the characteristics of the voice and carrier signals, you can create unique and creative sounds that enhance the overall listening experience. Feel free to experiment with different techniques and parameters to achieve your desired audio effects.

#vocoder #audioeffects