Problems with double / multiple buffering for low level wave input

Hi,
I am trying to get realtime throughput of the wave input to the wave output in full duplex.  I am using the code suggested by Creative Lab examples.  It works , except that in my MM_WIM_DATA  when I have passed on the buffer to the output, and unprepared the input header, preparing the just received buffer to recycle it for adding into the input queue seems to give problems. Error no. 7 memory alloc error.
here is the code for my mem allocation, start of input, and the function for processing MM_WIM_DATA.

      for (int i = 0; i < MAX_BUFFERS; i++)
      {
      
            hWaveInHdr[i] = GlobalAlloc(GHND | GMEM_SHARE, sizeof(WAVEHDR));
            lpWaveInHdr[i] = (LPWAVEHDR) GlobalLock(hWaveInHdr[i]);
            hWaveInBuffer[i] = GlobalAlloc(GHND | GMEM_SHARE, BUFFER_SIZE);
            lpWaveInBuffer[i] = (LPSTR) GlobalLock(hWaveInBuffer[i]);
            lpWaveInHdr[i]->lpData = lpWaveInBuffer[i];
            lpWaveInHdr[i]->dwBufferLength = BUFFER_SIZE;

            hWaveOutBuffer[i] = GlobalAlloc(GHND | GMEM_SHARE, BUFFER_SIZE);
            lpWaveOutBuffer[i] = (LPSTR) GlobalLock(hWaveOutBuffer[i]);
            hWaveOutHdr[i] = GlobalAlloc(GHND | GMEM_SHARE, sizeof(WAVEHDR));
            lpWaveOutHdr[i] = (LPWAVEHDR) GlobalLock(hWaveOutHdr[i]);
            lpWaveOutHdr[i]->lpData = lpWaveInBuffer[i];
            lpWaveOutHdr[i]->dwBufferLength = BUFFER_SIZE;

      }



///////////////////////////////////////////////////////////
      // Prepare and send input buffers to input device
      /////////////////////////
      nBufferIn = 0;
      nBufferOut = 0;
      for(int i=0; i<MAX_BUFFERS; i++)
      {
            // Prepare wave in header
            if (waveInPrepareHeader(hWaveIn, lpWaveInHdr[i], sizeof(WAVEHDR)))
            {
                  AfxMessageBox("OnPlay-error preparing header");
            }
            // Add buffer to recording queue
            if (waveInAddBuffer(hWaveIn, lpWaveInHdr[i], sizeof(WAVEHDR)))
            {
                  AfxMessageBox("OnPlay-error adding buffer");
            }
            else nBufferIn++;
      }


      // Start the wave input - begin sampling
      ///////////////////////
      waveInStart(hWaveIn);
      CDC* pDC = GetDC();
      pDC->TextOut(100,100,"Wave Started");
      ReleaseDC(pDC);


///////////////////////////////////////////////////////////
LONG CCreativeAudioView::OnMMWIMDATA (UINT wParam, LONG lParam)
{
//  Procedure to handle message from device driver saying it has filled a buffer
//  code from creative labs sample code

 nBufferIn--;
LPWAVEHDR lpWaveHdrTmp;
 lpWaveHdrTemp = (LPWAVEHDR) lParam;
lpWaveHdrTempOut = (LPWAVEHDR) lParam;
waveInUnprepareHeader(hWaveIn, lpWaveHdrTemp, sizeof(WAVEHDR));

// Send received buffer to output queue
      ///////////////////////////////////////////////////////////////
    waveOutPrepareHeader(hWaveOut, ((LPWAVEHDR) lParam),sizeof(WAVEHDR));
    waveOutWrite(hWaveOut, ((LPWAVEHDR) lParam), sizeof(WAVEHDR));
      
      //add another buffer to input queue
//////   THIS IS WHERE THE PROBLEMS COME IN, IT WORKS FOR 16 BUFFERS AND THEN SOUND STOPS AND I GET ERROR 7 EACH TIME I TRY TO PREPARE THE HEADER///////////      ////////////////////////////////////////////////////////
nError = waveInPrepareHeader( hWaveIn, lpWaveHdrTmp, sizeof(WAVEHDR));
if (nError != 0)
{
      strMessageText.Format("Error preparing next input header %d", nError);
      AfxMessageBox(strMessageText);
};
waveInAddBuffer(hWaveIn, lpWaveHdrTemp, sizeof(WAVEHDR));
nBufferIn++;
      return 0L;
}


i'D BE GRATEFUL FOR ANY HELP
Thanks

Kingpie
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alexxxConnect With a Mentor Commented:
Since you use the same buffers for both recording (wave in) and playback (wave out) you should synchronize their sending to these devices. Don't add buffers to wave in in its callback. Instead register callback function for wave out device and add buffer returned from wave out back to wave in. The data won't be lost because there are several buffers.


->Wave In-->(Wave In callback)-->Wave Out-->(Wave Out callback)-
^---<

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y96andhaCommented:
Does the waveinunprepareheader always succeed? Do you unprepare the waveout buffers?
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kingpieAuthor Commented:
It seems that waveInUnprepareHeader does always work.  The wave out buffers are unprepared in OnMM_WOM_DONE:

LONG CCreativeAudioView::OnMMWOMDONE (UINT wParam, LONG lParam)
{      
      lpWaveHdrTempOut = (LPWAVEHDR) lParam;
      waveOutUnprepareHeader(hWaveOut, lpWaveHdrTempOut,         sizeof(WAVEHDR));
      return 0L;
}
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kingpieAuthor Commented:
It seems that waveInUnprepareHeader does always work.  The wave out buffers are unprepared in OnMM_WOM_DONE:

LONG CCreativeAudioView::OnMMWOMDONE (UINT wParam, LONG lParam)
{      
      lpWaveHdrTempOut = (LPWAVEHDR) lParam;
      waveOutUnprepareHeader(hWaveOut, lpWaveHdrTempOut,         sizeof(WAVEHDR));
      return 0L;
}
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alexxxCommented:
So add buffers to Wave In on MM_WOM_DONE too and everything should be OK.
Good luck!
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kingpieAuthor Commented:
It works!  thanks very much. (and it makes sense!)
KingPie
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