DRV_OPEN

System message that notifies a video compression driver each time it is opened.

• Return zero to fail the call. A non-zero value is sent to the driver in the ID field each time DriverProc is sent a message with DrvSendMessage or DrvClose.

dwDriverIdentifier

Handle returned to the application opening the driver.

hDriver

Handle created by the system. This handle is returned to the application. A unique handle is created each time the driver is opened.

lParam1

Address of a zero-terminated string. The string contains any characters that follow the filename in the SYSTEM.INI file. If the device driver was opened by filename, or if there is no additional information, a NULL string or a NULL pointer is specified. Device drivers should verify that lParam1 is not NULL before dereferencing it.

lParam2

Address of an ICOPEN structure, or zero if the driver is opened only for configuration by the Multimedia property sheet of the Control Panel. If an ICOPEN structure is specified, the driver should verify the fccType member contains 'vidc'. This indicates the driver is opened as a video compressor.