Creating a Capture Buffer

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You create a capture buffer by calling the IDirectSoundCapture::CreateCaptureBuffer method of the DirectSoundCapture object.

One of the parameters to the method is a DSCBUFFERDESC structure that describes the characteristics of the desired buffer. The last member of this structure is a WAVEFORMATEX structure, which must be initialized with the details of the desired wave format. For more information on this structure, see Sound Data.

Note that if your application is using DirectSound as well as DirectSoundCapture, capture buffer creation can fail when the format of the capture buffer is not the same as that of the primary buffer. The reason is that some cards have only a single clock and cannot support capture and playback at two different frequencies.

The following example sets up a capture buffer that will hold 1 second of data.

/* In this example it is assumed that pDSC is a valid pointer to
   a DirectSoundCapture object. */
 
DSCBUFFERDESC              dscbd;
LPDIRECTSOUNDCAPTUREBUFFER pDSCB;
WAVEFORMATEX               wfx =
    {WAVE_FORMAT_PCM, 2, 44100, 176400, 4, 16, 0};
    // wFormatTag, nChannels, nSamplesPerSec, mAvgBytesPerSec,
    // nBlockAlign, wBitsPerSample, cbSize
dscbd.dwSize = sizeof(DSCBUFFERDESC);
dscbd.dwFlags = 0;
dscbd.dwBufferBytes = wfx.nAvgBytesPerSec;
dscbd.dwReserved = 0;
dscbd.lpwfxFormat = &wfx;
 
pDSCB = NULL;
 
HRESULT hr = pDSC->CreateCaptureBuffer(&dscbd, 
        &pDSCB, NULL);

 Last updated on Thursday, April 08, 2004

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