ThreeSineWaves.cpp

#include <iostream>
#include <cmath>
#include <fstream>
#define M_PI 3.1415926
using namespace std;

const int sampleRate = 44100;
const int bitDepth = 16;

class SineOscillator {
    float frequency, amplitude, angle = 0.0f, offset = 0.0f;
public:
    SineOscillator(float freq, float amp) : frequency(freq), amplitude(amp) {
        offset = 2 * M_PI * frequency / sampleRate;
    }
    float process() {
        auto sample = amplitude * sin(angle);
        angle += offset;
        return sample;
        // Asin(2pif/sr)
    }
};

void writeToFile(ofstream& file, int value, int size) {
    file.write(reinterpret_cast<const char*> (&value), size);
}

int main() {
  
    ofstream audioFile;
    audioFile.open("waveform.wav", ios::binary);

    //Header chunk
    audioFile << "RIFF";
    audioFile << "----";
    audioFile << "WAVE";

    // Format chunk
    audioFile << "fmt ";
    writeToFile(audioFile, 16, 4); // Size
    writeToFile(audioFile, 1, 2); // Compression code
    writeToFile(audioFile, 1, 2); // Number of channels
    writeToFile(audioFile, sampleRate, 4); // Sample rate
    writeToFile(audioFile, sampleRate * bitDepth / 8, 4); // Byte rate
    writeToFile(audioFile, bitDepth / 8, 2); // Block align
    writeToFile(audioFile, bitDepth, 2); // Bit depth

    //Data chunk
    audioFile << "data";
    audioFile << "----";

    int preAudioPosition = audioFile.tellp();

    auto maxAmplitude = pow(2, bitDepth - 1) - 1;

    int duration = 12;
    SineOscillator sineOscillator(440, 0.5);
    SineOscillator sineOscillator2(880, 0.5);
    SineOscillator sineOscillator3(880 * 2, 0.5);

    /* Audio render loop */
    for (int i = 0; i < sampleRate * duration; i++) {
        auto sample = sineOscillator.process();
        auto sample2 = sineOscillator2.process();
        auto sample3 = sineOscillator3.process();
        int intSample = static_cast<int> (
            (sample * maxAmplitude)  + 
            (sample2 * maxAmplitude) + 
            (sample3 * maxAmplitude)) 
            * .05;

        writeToFile(audioFile, intSample, 2);
    }
    int postAudioPosition = audioFile.tellp();

    audioFile.seekp(preAudioPosition - 4);
    writeToFile(audioFile, postAudioPosition - preAudioPosition, 4);

    audioFile.seekp(4, ios::beg);
    writeToFile(audioFile, postAudioPosition - 8, 4);

    audioFile.close();
    return 0;
}