Abrufen von Cd-Track-Specific-Informationen

Bei CD-Audiogeräten können Sie den Startort und die Länge eines Titels abrufen, indem Sie das flag MCI_TRACK angeben und das dwTrack-Element von MCI_STATUS_PARMS auf die gewünschte Titelnummer festlegen. Um den Startort eines Titels abzurufen, legen Sie das dwItem-Element auf MCI_STATUS_POSITION fest. Legen Sie dwItem auf MCI_STATUS_LENGTH fest, um die Länge eines Titels abzurufen. Im folgenden Beispiel werden beispielsweise die Gesamtanzahl der Titel auf der CD und der Startort der einzelnen Titel abgerufen. Anschließend wird die MessageBox-Funktion verwendet, um die Startpositionen der Tracks zu melden.

// Uses the MCI_STATUS command to get and display the 
// starting times for the tracks on a compact disc. 
// Returns 0L if successful; otherwise, it returns an 
// MCI error code.

DWORD DisplayCDTrackStartTimes(HWND hMainWnd)
{
    UINT wDeviceID;
    int i, iNumTracks;
    DWORD dwReturn;
    DWORD *pMem;
    TCHAR szTempString[64];
    TCHAR szTimeString[512] = TEXT("\0");  // Room for 20 tracks.
    MCI_OPEN_PARMS mciOpenParms;
    MCI_SET_PARMS mciSetParms;
    MCI_STATUS_PARMS mciStatusParms;

    // Open the device by specifying the device name.
    mciOpenParms.lpstrDeviceType = TEXT("cdaudio");
    if (dwReturn = mciSendCommand(NULL, MCI_OPEN,
        MCI_OPEN_TYPE, (DWORD_PTR)(LPVOID) &mciOpenParms))
    {
        // Failed to open device. 
        // Don't close device; just return error.
        return (dwReturn);
    }

    // The device opened successfully; get the device ID.
    wDeviceID = mciOpenParms.wDeviceID;

    // Set the time format to minute/second/frame (MSF) format. 
    mciSetParms.dwTimeFormat = MCI_FORMAT_MSF;
    if (dwReturn = mciSendCommand(wDeviceID, MCI_SET, 
        MCI_SET_TIME_FORMAT, 
        (DWORD_PTR)(LPVOID) &mciSetParms)) 
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (dwReturn);
    }

    // Get the number of tracks; 
    // limit it to the number that can be displayed (20).
    mciStatusParms.dwItem = MCI_STATUS_NUMBER_OF_TRACKS;
    if (dwReturn = mciSendCommand(wDeviceID, MCI_STATUS, 
        MCI_STATUS_ITEM, (DWORD_PTR)(LPVOID) &mciStatusParms)) 
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (dwReturn);
    }
    iNumTracks = (int)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 location and
    // build a string containing the starting locations.
    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_PTR)(LPVOID) &mciStatusParms)) 
        {
            mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
            return (dwReturn);
        }

        pMem[i-1] = (DWORD)mciStatusParms.dwReturn;

        _stprintf_s(szTempString, 
            TEXT("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]));

        _tcscat_s(szTimeString, szTempString);
    }

    // Use MessageBox to display starting times.
    MessageBox(
        hMainWnd, 
        szTimeString, 
        TEXT("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);
}