Audio programming #1 Create & write to a WAV file

wav.cpp

#include <iostream>
#include <fstream>
#include <cmath>


using namespace std;

// Riff Chunk
const string RIFF_CHUNK_ID = "RIFF";
const string RIFF_CHUNK_SIZE = "----";
const string RIFF_FORMAT = "WAVE";
const string FMT_SUB_CHUNK_1_ID = "fmt ";
const int FMT_SUB_CHUNK_1_SIZE = 16;
const int FMT_AUDIO_FORMAT = 1;
const int FMT_NUMB_CHANNELS = 2;
const int FMT_SAMPLE_RATE = 44100;
const int FMT_BYTE_RATE = FMT_SAMPLE_RATE * FMT_NUMB_CHANNELS * (FMT_SUB_CHUNK_1_SIZE / 8);
const int FMT_BLOCK_ALIGN = FMT_NUMB_CHANNELS * (FMT_SUB_CHUNK_1_SIZE / 8);
const int FMT_BITS_PER_SAMPLE = 16;
const string DATA_SUB_CHUNK_2_ID = "data";
const string DATE_SUB_CHUNK_2_SIZE = "----";
const int DURATION = 2;
const int MAX_AMPLITUDE = 32760;
const double FREQUENCY_VALUE = 250;

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


int main(int argc, const char * argv[])
{
    string file_name = "test.wav";
    ofstream wav;
    wav.open(file_name, ios::binary);
    
    if (wav.is_open())
    {
        wav << RIFF_CHUNK_ID;
        wav << RIFF_CHUNK_SIZE;
        wav << RIFF_FORMAT;
        wav << FMT_SUB_CHUNK_1_ID;
        _write_as_bytes(wav, FMT_SUB_CHUNK_1_SIZE, 4);
        _write_as_bytes(wav, FMT_AUDIO_FORMAT, 2);
        _write_as_bytes(wav, FMT_NUMB_CHANNELS, 2);
        _write_as_bytes(wav, FMT_SAMPLE_RATE, 4);
        _write_as_bytes(wav, FMT_SAMPLE_RATE, 4);
        _write_as_bytes(wav, FMT_BYTE_RATE, 4);
        _write_as_bytes(wav, FMT_BLOCK_ALIGN, 2);
        _write_as_bytes(wav, FMT_BITS_PER_SAMPLE, 2);
        wav << DATA_SUB_CHUNK_2_ID;
        wav << DATE_SUB_CHUNK_2_SIZE;
        
        int start_audio = wav.tellp();
        
        for (int i = 0; i > FMT_SAMPLE_RATE * DURATION; i++)
        {
            double amplitude = (double)i / FMT_SAMPLE_RATE * MAX_AMPLITUDE;
            double value = sin((2 * 3.14 * i * FREQUENCY_VALUE) / FMT_SAMPLE_RATE);
            double channel1 = amplitude * value;
            double channel2 = (MAX_AMPLITUDE - amplitude) * value;
            
            _write_as_bytes(wav, channel1, 2);
            _write_as_bytes(wav, channel2, 2);
            
        }
        
        int end_audio = wav.tellp();
        
        wav.seekp(start_audio - 4);
        _write_as_bytes(wav, end_audio - start_audio, 4);
        
        wav.seekp(4, ios::beg);
        _write_as_bytes(wav, end_audio - 8, 4);
        
    }
    wav.close();
    
    return 0;
}