This topic applies only to applications written in C++.

To prepare for writing to a wave file, the application must first declare four variables to be passed to the functions in Wavwrite.cpp:

WAVEFORMATEX  wfx;            // Wave format info
HMMIO         hmmio;          // File handle
MMCKINFO      mmckinfoData;   // Chunk info
MMCKINFO      mmckinfoParent; // Parent chunk (file) info
 

You must also initialize the WAVEFORMATEX structure with the format of the capture buffer.

Now you call the WaveOpenFile function, passing in the desired filename and the addresses of the global variables. The function creates the file and writes some header information. Like other functions in Wavwrite.cpp, WaveOpenFile returns zero if successful.

if (WaveOpenFile(pszFileName, &hmmio, &wfx, 
        &mmckinfoData, &mmckinfoParent))
{
    // Failure
}
 

Next, call the WaveStartDataWrite function, which initializes the data chunk.

if (WaveStartDataWrite(&hmmio, &mmckinfoData, &mmioinfo))
{
     // Failure
}
 

The file is now ready to receive data. The following fragment illustrates how data might be copied from a capture buffer to a file.

/* It is assumed that the following variables contain
   valid assignments:
LPDIRECTSOUNDCAPTUREBUFFER lpdscb;    // Capture buffer
DSCBUFFERDESC    dscbDesc;            // Capture buffer description
DWORD            dwReadCursor;        // Internal cursor in buffer
DWORD            dwNumBytes;          // Bytes available
DWORD            dwTotalBytesWritten; // Running total in file
*/
 
LPBYTE pbInput1, pbInput2; // Pointers to data in buffer
DWORD  cbInput1, cbInput2; // Count of bytes in locked portion
UINT   BytesWritten;       // Count of bytes written to file
 
if FAILED(hr = lpdscb->Lock(dwReadCursor, dwNumBytes,
                      (LPVOID *)&pbInput1, &cbInput1, 
                      (LPVOID *)&pbInput2, &cbInput2, 0))
{
    // Failure
}
else
{
    if (WaveWriteFile(hmmio, cbInput1, pbInput1, &mmckinfoData,
                    &dwBytesWritten, &mmioinfo))
    {
        // Failure
    }
    else dwTotalBytesWritten += BytesWritten; 
    if (pbInput2 != NULL) 
    {
        if (WaveWriteFile(hmmio, cbInput2, pbInput2, &mmckinfoData,
                    &BytesWritten, &mmioinfo))
        {
            // Failure
        }
        else dwTotalBytesWritten += BytesWritten; 
 
    }
    lpdscb->Unlock(pbInput1, cbInput1, pbInput2, cbInput2);
 
    // Increment internal cursor, compensating for wrap around
    dwReadCursor += dwNumBytes;
    while (dwReadCursor >= dscbDesc.dwBufferBytes)
                dwMyReadCursor -= dscbDesc.dwBufferBytes;
 
}
 

When you are finished capturing data, you close the file:

WaveCloseWriteFile(&hmmio, &mmckinfoData, 
        &mmckinfoParent, &mmioinfo,
        dwTotalBytesWritten / (wfx.wBitsPerSample / 8));
 

The WaveCloseWriteFile function calculates the total number of samples in the file and writes this number to the data chunk header.