December 28, 2021
Unless it's compressed, a WAV file generally consists of raw PCM data plus 44 bytes of header, and is a relatively easy format to generate. The following code represents a header for a 44.1kHz 16bit mono WAV file. By changing num_channels, you can make it a header for stereo. The length of the raw PCM data in bytes should be passed as a constructor parameter.
#include <cstdint>
struct WaveHeader {
explicit WaveHeader(int32_t raw_length) {
subchunk2_size = raw_length;
chunk_size = raw_length + 36;
byte_rate = sample_rate * num_channels * bits_per_sample / 8;
block_align = num_channels * bits_per_sample / 8;
}
char chunk_id[4] = {'R', 'I', 'F', 'F'};
int32_t chunk_size;
char format[4] = {'W', 'A', 'V', 'E'};
char subchunk1_id[4] = {'f', 'm', 't', ' '};
int32_t subchunk1_size = 16;
int16_t audio_format = 1;
int16_t num_channels = 1;
int32_t sample_rate = 44100;
int32_t byte_rate;
int16_t block_align;
int16_t bits_per_sample = 16;
char subchunk2_id[4] = {'d', 'a', 't', 'a'};
int32_t subchunk2_size;
};The following code generates test.wav, which contains 440Hz sine wave for 1 second.
#include <cmath>
#include <vector>
int main(int argc, char *argv[]) {
const double pi = acos(-1);
std::vector<int16_t> raw(44100);
for (int i = 0; i < 44100; ++i) {
double t = i / 44100.0;
raw[i] = 8192 * sin(440.0 * 2.0 * pi * t);
}
WaveHeader header(sizeof(int16_t) * raw.size());
FILE *fp = fopen("test.wav", "wb");
fwrite(&header, sizeof(WaveHeader), 1, fp);
fwrite(&raw[0], sizeof(int16_t), raw.size(), fp);
fclose(fp);
return 0;
}