Windows c++ waveInStart how to access to recorded data and managing it?

Question

I want to record some audio from microphone under Windows, so I use the wave API.

This is what I do

QByteArray tmp;
QByteArray data;
char dst[SAMPLES_TO_SEND];
qint64 tot=0;
const int NUMPTS = SAMPLES_TO_SEND*3;
int sampleRate = 48000;
short int waveIn[NUMPTS];   // 'short int' is a 16-bit type; I request 16-bit samples below
// for 8-bit capture, you'd use 'unsigned char' or 'BYTE' 8-bit types

HWAVEIN      hWaveIn;
WAVEHDR      WaveInHdr;
MMRESULT result;

// Specify recording parameters
WAVEFORMATEX pFormat;
pFormat.wFormatTag=WAVE_FORMAT_PCM;     // simple, uncompressed format
pFormat.nChannels=1;                    //  1=mono, 2=stereo
pFormat.nSamplesPerSec=sampleRate;      // 48000
pFormat.nAvgBytesPerSec=sampleRate*2;   // = nSamplesPerSec * n.Channels * wBitsPerSample/8
pFormat.nBlockAlign=2;                  // = n.Channels * wBitsPerSample/8
pFormat.wBitsPerSample=16;              //  16 for high quality, 8 for telephone-grade
pFormat.cbSize=0;

result = waveInOpen(&hWaveIn, WAVE_MAPPER,&pFormat, 0L, 0L, WAVE_FORMAT_DIRECT);

if (result)
{
    WCHAR fault[256];
    waveInGetErrorText(result, fault, 256);
    return -1;
}

// Set up and prepare header for input
WaveInHdr.lpData = (LPSTR)waveIn;
WaveInHdr.dwBufferLength = NUMPTS*2;
WaveInHdr.dwBytesRecorded=0;
WaveInHdr.dwUser = 0L;
WaveInHdr.dwFlags = 0L;
WaveInHdr.dwLoops = 0L;
waveInPrepareHeader(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));

// Insert a wave input buffer
result = waveInAddBuffer(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));
if (result)
{
    return -1;
}

// Commence sampling input
result = waveInStart(hWaveIn);
if (result)
{
 return -1;
}

At this point, what I must do to access and managing recorded data? My final goal is to continuously recording small data (I want every time exactly 512 sample) subsampling what I recorded to have a 16 kHz samples (so I would divide data by 3) and apply a ulaw algorithm and send everything via udp. This is why my buffer is so small (NUMPTS = 1536 shorts -> 3072 bytes). After a sleep of 100 milli seconds, I have checked what there is in waveIn, but is all 0... (well, of course my microphone is working correctly)

Answer 1

The waveInOpen function provides four callback options that are for notifying you when a buffer has been filled. Use one of those choices.

You should also allocate a second buffer and output it immediately after the first. It will be queued in the driver and switched to seamlessly when the first buffer has been filled.