Why is this simple audio code not creating any sound? - audio

Question

I am learning how to generate sound using Windows and c++. I was trying to use a simple tutorial, but the code only creates silence. What did I do wrong? I tested with some print commands (which I removed) and the code seems to run to completion. Other sounds (from other programs, of course) play fine, and there are no error messages. I think the code looks right, but I am clearly not capable of judging that...
#include <iostream>
#include <cmath>
#include <windows.h>
#include <mmsystem.h>
// Sample rate
const int SAMPLE_RATE = 44100;
// Frequency of the sine wave
const int FREQUENCY = 440;
int main()
{
// Open the default audio device for output
HWAVEOUT hWaveOut = NULL;
waveOutOpen(&hWaveOut, WAVE_MAPPER, NULL, 0, 0, CALLBACK_NULL);
// Create a WAVEHDR structure to describe the waveform data
WAVEHDR waveHdr;
memset(&waveHdr, 0, sizeof(waveHdr));
// Allocate memory for the waveform data
const int BUFFER_SIZE = SAMPLE_RATE * sizeof(short);
short* samples = (short*)malloc(BUFFER_SIZE);
// Generate the sine wave samples
for (int i = 0; i < SAMPLE_RATE; ++i)
{
float t = i / float(SAMPLE_RATE);
float sample = sin(2 * M_PI * FREQUENCY * t);
samples[i] = short(sample * 32767);
}
// Set up the WAVEHDR structure
waveHdr.lpData = (LPSTR)samples;
waveHdr.dwBufferLength = BUFFER_SIZE;
// Prepare the waveform data for playback
waveOutPrepareHeader(hWaveOut, &waveHdr, sizeof(waveHdr));
// Play the waveform data
waveOutWrite(hWaveOut, &waveHdr, sizeof(waveHdr));
// Wait until the sound finishes playing
while (waveHdr.dwFlags & WHDR_DONE != WHDR_DONE)
{
// Do nothing
}
// Clean up
waveOutUnprepareHeader(hWaveOut, &waveHdr, sizeof(waveHdr));
waveOutClose(hWaveOut);
free(samples);
return 0;
}

Answer 1

You need to set a WAVEFORMATEX structure before opening and playing audio (more information can be found here https://learn.microsoft.com/en-us/windows/win32/api/mmeapi/ns-mmeapi-waveformatex ).
WAVEFORMATEX wfex;
wfex.wFormatTag = WAVE_FORMAT_PCM;
wfex.nChannels = 1;
wfex.wBitsPerSample = 16; //number of bits per sample
wfex.nAvgBytesPerSec = 1 * 44100 * 2;//numChannels * numSamplesPerSec * numBytesPerSample
wfex.nBlockAlign = 1 * 2;//numChannels * numBytesPerSample;
wfex.cbSize = 0;
HWAVEOUT hWaveOut = NULL;
MMRESULT mm = waveOutOpen(&hWaveOut, WAVE_MAPPER, &wfex, 0, 0, CALLBACK_NULL);
if (mm != MMSYSERR_NOERROR){
std::string errorMsg = getWaveError(mm);
//display the message etc
}
In case of an error, you can query the mm variable and display an appropriate message that could help you identify the problem.
std::string getWaveError(MMRESULT mm){
std::string errorMsg;
switch (mm) {
case MMSYSERR_INVALHANDLE:
errorMsg = "Wave exception: Invalid handle";
break;
case MMSYSERR_NOMEM:
errorMsg = "Wave exception: Not enough memory";
break;
case MMSYSERR_NODRIVER:
errorMsg = "Wave exception: No driver present";
break;
case WAVERR_UNPREPARED:
errorMsg = "Wave exception: Unprepared buffer";
break;
case MMSYSERR_HANDLEBUSY:
errorMsg = "Wave exception: Handle busy";
break;
case MMSYSERR_ALLOCATED:
errorMsg = "Wave exception: Device already allocated";
break;
case WAVERR_BADFORMAT:
errorMsg = "Wave exception: Unsupported wave format";
break;
default:
errorMsg = "Wave exception: Unknown error: Code " + mm;
;
}
return errorMsg;
}
Hope this helps.