Use the MCI_STATUS command along with the MCI_STATUS_PARMS parameter block to get information about the status of an open device and its associated device element. MMSYSTEM.H defines the MCI_STATUS_PARMS parameter block as follows:
typedef struct {
DWORD dwCallback; /* callback for MCI_NOTIFY flag */
DWORD dwReturn; /* status information is returned here */
DWORD dwItem; /* identifies status item */
DWORD dwTrack; /* track number */
} MCI_STATUS_PARMS;
Before using the MCI_STATUS command, you must identify the status item to query for by putting a constant in the dwItem field of the parameter block. The following list shows different status items you can query for and the corresponding constant for each item for different types of audio devices:
All Audio Devices
| Constant | Status Item |
| MCI_STATUS_LENGTH | Length of the media |
| MCI_STATUS_POSITION | Current position |
| MCI_STATUS_MODE | Current mode |
| MCI_STATUS_TIME_FORMAT | Time format |
| MCI_STATUS_READY | Ready state |
Waveform Devices
| Constant | Status Item |
| MCI_WAVE_STATUS_BLOCKALIGN | ||
| Block alignment | ||
| MCI_WAVE_STATUS_FORMATTAG | ||
| Format tag | ||
| MCI_WAVE_STATUS_CHANNELS | ||
| Number of channels | ||
| MCI_WAVE_STATUS_SAMPLESPERSEC | ||
| Sample rate | ||
| MCI_WAVE_STATUS_AVGBYTESPERSEC | ||
| Average bytes per second | ||
| MCI_WAVE_STATUS_BITSPERSAMPLE | ||
| Bits per sample (in PCM format files) | ||
| MCI_WAVE_STATUS_LEVEL | ||
| Record level | ||
Compact Disc Devices
| Constant | Status Item |
| MCI_STATUS_NUMBER_OF_TRACKS | Number of tracks |
| MCI_STATUS_MEDIA_PRESENT | Media present |
| MCI_STATUS_CURRENT_TRACK | Current track |
MIDI Sequencer Devices
| CI_SEQ_STATUS_TEMPO | Tempo |
| CI_SEQ_STATUS_PORT | Port |
| MCI_SEQ_STATUS_OFFSET | SMPTE offset |
| MCI_SEQ_STATUS_DIVTYPE | Division type of file |
For compact disc devices, you can get the starting position and length of a track by specifying the MCI_TRACK flag and setting the dwTrack field of MCI_STATUS_PARMS to the desired track number. To get the starting position of a track, set the dwItem field to MCI_STATUS_POSITION. To get the length of a track, set dwItem to MCI_STATUS_LENGTH. For example, the following function gets the total number of tracks on the disc and the starting position of each track. It then uses the MessageBox function to report the starting positions of the tracks.
/* Uses the MCI_STATUS command to get and display the starting times
* for the tracks on a compact disc. Returns 0L on success; otherwise,
* it returns an MCI error code.
*/
DWORD getCDTrackStartTimes(void)
{
UINT wDeviceID;
int i, iNumTracks;
DWORD dwReturn;
DWORD dwPosition;
DWORD *pMem;
char szTempString[64];
char szTimeString[512] = "\0"; // big enough for 20 tracks
MCI_OPEN_PARMS mciOpenParms;
MCI_SET_PARMS mciSetParms;
MCI_STATUS_PARMS mciStatusParms;
/* Open the compact disc device by specifying the device name.
*/
mciOpenParms.lpstrDeviceType = "cdaudio";
if (dwReturn = mciSendCommand(NULL, MCI_OPEN,
MCI_OPEN_TYPE,
(DWORD)(LPVOID) &mciOpenParms))
{
/* Failed to open device; don't have to close it, just return error.
*/
return (dwReturn);
}
/* Device opened successfully, get the device ID.
*/
wDeviceID = mciOpenParms.wDeviceID;
/* Set the time format to minute/second/frame format.
*/
mciSetParms.dwTimeFormat = MCI_FORMAT_MSF;
if (dwReturn = mciSendCommand(wDeviceID, MCI_SET, MCI_SET_TIME_FORMAT,
(DWORD)(LPVOID) &mciSetParms))
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (dwReturn);
}
/* Get the number of tracks; limit to number we can display (20).
*/
mciStatusParms.dwItem = MCI_STATUS_NUMBER_OF_TRACKS;
if (dwReturn = mciSendCommand(wDeviceID, MCI_STATUS, MCI_STATUS_ITEM,
(DWORD)(LPVOID) &mciStatusParms))
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (dwReturn);
}
iNumTracks = mciStatusParms.dwReturn;
iNumTracks = min(iNumTracks, 20);
/* Allocate memory to hold starting positions.
*/
pMem = (DWORD *)LocalAlloc(LPTR, iNumTracks * sizeof(DWORD));
if (pMem == NULL)
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (-1);
}
/* For each track, get and save the starting position and
* build a string containing starting positions.
*/
for(i=1; i<=iNumTracks; i++)
{
mciStatusParms.dwItem = MCI_STATUS_POSITION;
mciStatusParms.dwTrack = i;
if (dwReturn = mciSendCommand(wDeviceID, MCI_STATUS,
MCI_STATUS_ITEM | MCI_TRACK,
(DWORD)(LPVOID) &mciStatusParms))
{
mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
return (dwReturn);
}
pMem[i-1] = mciStatusParms.dwReturn;
wsprintf(szTempString, "Track %2d - %02d:%02d:%02d\n",
i,
MCI_MSF_MINUTE(pMem[i-1]),
MCI_MSF_SECOND(pMem[i-1]),
MCI_MSF_FRAME(pMem[i-1]));
lstrcat(szTimeString, szTempString);
}
/* Use MessageBox to display starting times.
*/
MessageBox(hMainWnd, szTimeString, "Track Starting Position",
MB_ICONINFORMATION);
/* Free memory and close the device.
*/
LocalFree((HANDLE) pMem);
if (dwReturn = mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL))
{
return (dwReturn);
}
return (0L);
}