To prepare for writing to a wave file, the application must first declare four variables to be passed to the functions in Wave.c:
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 WaveCreateFile 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 Wave.c, WaveCreateFile returns zero if successful.
if (WaveCreateFile(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 wraparound
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.