MCI supports recording with waveform audio devices. You can insert or overwrite recorded information into an existing file or record into a new file. To record to an existing file, open a waveform device and device element as you would normally. To record into a new file, specify a zero-length filename for the device element when you open the device.
When MCI creates a new file for recording, the waveform data format is set to a default format specified by the device driver. To use a format other than the default format, you can use MCI_SET to change the format.
To begin recording, use the MCI_RECORD command along with the MCI_RECORD_PARMS parameter block. MMSYSTEM.H defines the MCI_RECORD_PARMS parameter block as follows:
typedef struct {
DWORD dwCallback; /* callback for MCI_NOTIFY flag */
DWORD dwFrom; /* record begin position */
DWORD dwTo; /* record end position */
} MCI_RECORD_PARMS;
If you record to an existing file, you can use the MCI_TO and MCI_FROM flags to specify beginning and ending points for recording. For example, if you record to an existing file 20 seconds long, and you begin recording at 5 seconds and end recording at 10 seconds, you will have a recording 25 seconds long, as shown in the following illustration:
This illustration is not available for this release
If you don't specify an ending position, recording continues until you send an MCI_STOP command, or until the driver runs out of free disk space. If you record to a new file, you can omit the MCI_FROM flag or set it to 0 to start recording at the beginning of a new file. You can specify an end position to terminate recording when recording to a new file.
If you record with overwrite mode to an existing file, you can use the MCI_TO and MCI_FROM flags to specify beginning and ending points of the waveform section that is overwritten. For example, if you record to an existing file 20 seconds long, and you begin recording at 5 seconds and end recording at 10 seconds, you still have a recording 20 seconds long, but the section beginning at 5 seconds and ending at 10 seconds has been replaced.
When recording is complete, use the MCI_SAVE command along with the MCI_SAVE_PARMS parameter block to save the recording before closing the device. MMSYSTEM.H defines the MCI_SAVE_PARMS parameter block as follows:
typedef struct {
DWORD dwCallback; /* callback for MCI_NOTIFY flag */
LPCSTR lpfilename; /* filename for saved file */
} MCI_SAVE_PARMS;
If you close the device without saving, the recorded data is lost.
To get the level of the input signal before recording on a PCM waveform input device, use the MCI_STATUS command. Specify the MCI_STATUS_ITEM flag and set dwItem in MCI_STATUS_PARMS to MCI_WAVE_STATUS_LEVEL. The average input signal level is returned in the dwReturn field of the MCI_STATUS_PARMS parameter block. The left-channel value is in the high-order word and the right- or mono-channel value is in the low-order word, as shown in the following illustration:
This illustration is not available for this release
The input level is represented as an unsigned value. For 8-bit samples, this value ranges from 0 through 127 (0x7F). For 16-bit samples, it ranges from 0 through 32,767 (0x7FFF).
The following function opens a waveform audio device with a new file, records for the specified time, plays the recording, and prompts the user to see if the recording should be saved as a file:
/* Uses the MCI_OPEN, MCI_RECORD, MCI_SAVE commands to record and
* save a waveform audio file. Returns 0L on success; otherwise,
* it returns an MCI error code.
*/
DWORD recordWAVEFile(DWORD dwMilliSeconds)
{
UINT wDeviceID;
DWORD dwReturn;
MCI_OPEN_PARMS mciOpenParms;
MCI_RECORD_PARMS mciRecordParms;
MCI_SAVE_PARMS mciSaveParms;
MCI_PLAY_PARMS mciPlayParms;
/* Open a waveform device with a new file for recording.
*/
mciOpenParms.lpstrDeviceType = "waveaudio";
mciOpenParms.lpstrElementName = "";
if (dwReturn = mciSendCommand(0, MCI_OPEN,
MCI_OPEN_ELEMENT | MCI_OPEN_TYPE,
(DWORD)(LPVOID) &mciOpenParms))
{
/* Failed to open device; don't close it, just return error.
*/
return (dwReturn);
}
/* Device opened successfully, get the device ID.
*/
wDeviceID = mciOpenParms.wDeviceID;
/* Begin recording and record for the specified number of milliseconds.
* Wait for recording to complete before continuing. Assume the
* default time format for the waveform device (milliseconds).
*/
mciRecordParms.dwTo = dwMilliSeconds;
if (dwReturn = mciSendCommand(wDeviceID, MCI_RECORD, MCI_TO | MCI_WAIT,
(DWORD)(LPVOID) &mciRecordParms))
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (dwReturn);
}
/* Play the recording and query user to save the file.
*/
mciPlayParms.dwFrom = 0L;
if (dwReturn = mciSendCommand(wDeviceID, MCI_PLAY,
MCI_FROM | MCI_WAIT,
(DWORD)(LPVOID) &mciPlayParms))
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (dwReturn);
}
if (MessageBox(hMainWnd, "Do you want to save this recording?",
"", MB_YESNO) == IDNO)
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (0L);
}
/* Save the recording to a file named "tempfile.wav". Wait for
* the operation to complete before continuing.
*/
mciSaveParms.lpfilename = "tempfile.wav";
if (dwReturn = mciSendCommand(wDeviceID, MCI_SAVE,
MCI_SAVE_FILE | MCI_WAIT,
(DWORD)(LPVOID) &mciSaveParms))
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (dwReturn);
}
return (0L);
}