The MCI_RESERVE command allocates contiguous disk space for the workspace of the device driver instance for use with subsequent recording. Digital-video devices recognize this command.
MCIERROR mciSendCommand(MCIDEVICEID wDeviceID, MCI_RESERVE,
DWORD dwFlags, (DWORD) (LPMCI_DGV_RESERVE_PARMS) lpReserve);
Returns zero if successful or an error otherwise.
If the workspace contains unsaved data, this data is lost. If disk space is not reserved prior to recording, the MCI_RECORD command performs an implied reserve with device-specific default parameters. On some implementations, reserve is not required and might be ignored by the device driver. Explicitly reserving space gives you better control over when the delay for disk allocation occurs, how much space is allocated, and where the disk space is allocated. The amount and location of disk space already reserved for this device instance can be changed by issuing MCI_RESERVE again. Any allocated and still unused disk space is not deallocated until any recorded data is saved or until the device driver instance is closed.
If video is turned off with the MCI_OFF flag of the MCI_SETVIDEO command, the space reserved does not include any video. If audio is turned off with the MCI_OFF flag of the MCI_SETAUDIO command, the space reserved does not include any audio. If both audio and video are turned off or if the requested size is zero, no space is reserved and any existing reserved space is deallocated.
The following additional flags apply to digital-video devices:
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in mmsystem.h.
MCI Overview, MCI Commands, MCI_DGV_RESERVE_PARMS, MCI_RECORD, MCI_SETAUDIO, MCI_SETVIDEO