The entry-point function, DriverProc, processes messages sent by the system to the driver as the result of an application call to a video compression and decompression function. For example, when an application opens a video compression and decompression driver, the system sends the specified driver a DRV_OPEN message. The driver's DriverProc function receives and processes this message. Your DriverProc should return ICERR_UNSUPPORTED for any messages that it does not handle.
Note Your driver should respond to all system messages. If supplemental information is not provided for them in this chapter, use the definitions provided in the Microsoft Win32 Programmer's Reference.