Audio effects play a crucial role in enhancing the overall listening experience. One of the powerful techniques used in audio processing is cross synthesis. Cross synthesis involves combining two or more audio signals to create new and interesting sounds. In this blog post, we will explore how to implement audio effects using cross synthesis in C++.

Introduction to Cross Synthesis

Cross synthesis is based on the concept of spectral merging of audio signals. It involves decomposing the audio signals into their frequency components using techniques such as Fast Fourier Transform (FFT). Once the signals are in the frequency domain, we can manipulate their spectral characteristics to create unique sounds. The modified frequency components are then transformed back to the time domain using inverse FFT to obtain the cross-synthesized audio.

Setting up the Project

Before we dive into the implementation, make sure you have a C++ development environment set up on your computer. You will also need a library that provides FFT functionality, such as FFTW or KissFFT. Once you have these dependencies installed, create a new C++ project and include the necessary headers.

Loading Audio Signals

To begin, we need to load the audio signals that we want to cross synthesize. Use a library like PortAudio or libsndfile to read audio files into memory as arrays of samples. Convert the audio signals to mono if necessary, as cross synthesis typically works best with monophonic signals.

#include <iostream>
#include <vector>
#include <portaudio.h>

// Load audio signals from files or record using PortAudio

std::vector<float> loadAudioSignal(const std::string& filename) {
    // Load audio signal from file
    // Convert to mono if necessary
    // Return as vector of float samples
}

int main() {
    std::vector<float> signalA = loadAudioSignal("sampleA.wav");
    std::vector<float> signalB = loadAudioSignal("sampleB.wav");
    
    // Cross synthesis implementation goes here
}

Cross Synthesis Implementation

Now that we have the audio signals loaded, let’s implement the cross synthesis algorithm. Here’s a high-level overview of how it works:

1. Perform FFT on both input signals to obtain their frequency representations.
2. Manipulate the spectral characteristics of both signals.
3. Combine the modified frequency components of the signals.
4. Perform inverse FFT to obtain the cross-synthesized audio.

#include <cmath>

// Cross synthesis implementation

void crossSynthesis(const std::vector<float>& signalA, const std::vector<float>& signalB, std::vector<float>& output) {
    // Perform FFT on both input signals
    // Manipulate spectral characteristics
    // Combine frequency components
    // Perform inverse FFT to obtain cross-synthesized audio
}

int main() {
    std::vector<float> signalA = loadAudioSignal("sampleA.wav");
    std::vector<float> signalB = loadAudioSignal("sampleB.wav");
    
    std::vector<float> output(signalA.size());
    
    crossSynthesis(signalA, signalB, output);
    
    // Save output as new audio file
}

Experimenting with Cross Synthesis

Now that your cross synthesis implementation is working, it’s time to experiment and explore the possibilities. You can adjust the spectral characteristics of the signals, such as the magnitudes and phases, to achieve different effects. By carefully manipulating these parameters, you can create unique and intriguing audio textures.

Conclusion

Cross synthesis is a powerful technique that allows us to create complex and interesting audio effects by combining different signals. By manipulating the frequency domain representations of audio signals, we can achieve a wide range of unique sounds. The implementation provided in this blog post serves as a starting point for exploring cross synthesis in your own audio applications.

#audioeffects #crosssynthesis