dwFlags = (DWORD) lParam1; // MCI flags
lpMCI_OPEN_PARMS =
(LPMCI_OPEN_PARMS) lParam2; // Pointer to MCI_OPEN_PARMS
// structure.
This message is the version of the MCI_OPEN command sent by MCI to an MCI device.
An MCI internal procedure intercepts the MCI_OPEN message sent by an application. After processing, the procedure calls the device with DRV_OPEN and MCI_OPEN_DRIVER.