read an electric signal through sound card c++

read an electric signal through sound card

  CWaveFile   g_pWaveFile;
    WAVEFORMATEX  wfxInput;
     
    ZeroMemory( &wfxInput, sizeof(wfxInput));
    wfxInput.wFormatTag = WAVE_FORMAT_PCM;
    wfxInput.nSamplesPerSec = 22050
    wfxInput.wBitsPerSample =  8; 
    wfxInput.nChannels = 1;
    wfxInput.nBlockAlign = 
        wfxInput.nChannels * (wfxInput.wBitsPerSample / 8);
    wfxInput.nAvgBytesPerSec = 
        wfxInput.nBlockAlign * wfxInput.nSamplesPerSec;
     
    g_pWaveFile = new CWaveFile;
    if (FAILED(g_pWaveFile->Open("mywave.wav", &wfxInput,
        WAVEFILE_WRITE)))
    {
      g_pWaveFile->Close();
    }



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HRESULT RecordCapturedData() 
    {
      HRESULT hr;
      VOID* pbCaptureData  = NULL;
      DWORD dwCaptureLength;
      VOID* pbCaptureData2 = NULL;
      DWORD dwCaptureLength2;
      VOID* pbPlayData   = NULL;
      UINT  dwDataWrote;
      DWORD dwReadPos;
      LONG lLockSize;
     
      if (NULL == g_pDSBCapture)
          return S_FALSE;
      if (NULL == g_pWaveFile)
          return S_FALSE;
     
      if (FAILED (hr = g_pDSBCapture->GetCurrentPosition( 
        NULL, &dwReadPos)))
          return hr;
     
      // Lock everything between the private cursor 
      // and the read cursor, allowing for wraparound.
     
      lLockSize = dwReadPos - g_dwNextCaptureOffset;
      if( lLockSize < 0 ) lLockSize += g_dwCaptureBufferSize;
     
      if( lLockSize == 0 ) return S_FALSE;
     
      if (FAILED(hr = g_pDSBCapture->Lock( 
            g_dwNextCaptureOffset, lLockSize, 
            &pbCaptureData, &dwCaptureLength, 
            &pbCaptureData2, &dwCaptureLength2, 0L)))
        return hr;
     
      // Write the data. This is done in two steps
      // to account for wraparound.
    
      if (FAILED( hr = g_pWaveFile->Write( dwCaptureLength, 
          (BYTE*)pbCaptureData, &dwDataWrote)))
        return hr; 
     
      if (pbCaptureData2 != NULL)
      {
        if (FAILED(hr = g_pWaveFile->Write( 
            dwCaptureLength2, (BYTE*)pbCaptureData2, 
            &dwDataWrote)))
          return hr; 
      }
     
      // Unlock the capture buffer.
     
     g_pDSBCapture->Unlock( pbCaptureData, dwCaptureLength, 
        pbCaptureData2, dwCaptureLength2  );
      
      // Move the capture offset forward.
     
      g_dwNextCaptureOffset += dwCaptureLength; 
      g_dwNextCaptureOffset %= g_dwCaptureBufferSize; 
      g_dwNextCaptureOffset += dwCaptureLength2; 
      g_dwNextCaptureOffset %= g_dwCaptureBufferSize; 
     
      return S_OK;
    }