MCI_RESERVE
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);
Parameters
wDeviceID
Device
identifier of the MCI device that is to receive the command message.
dwFlags
MCI_NOTIFY,
MCI_WAIT, or MCI_TEST. For information about these flags, see The Wait,
Notify, and Test Flags.
lpReserve
Address of an
MCI_DGV_RESERVE_PARMS
structure.
Return Values
Returns zero
if successful or an error otherwise.
Remarks
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:
MCI_DGV_RESERVE_IN
The lpstrPath
member of the structure identified by lpReserve contains an address of a
buffer containing the location of a temporary file. The buffer contains only
the drive and directory path of the file used to hold recorded data; the
filename is specified by the device driver. This temporary file is deleted when
the device instance is closed unless it is explicitly saved. If this flag is
omitted, the device driver specifies where disk space is allocated.
MCI_DGV_RESERVE_SIZE
The dwSize
member of the structure identified by lpReserve specifies the
approximate amount of disk space to reserve in the workspace for recording. The
value is specified in the current time format. The amount of disk space is
estimated from the requested time and from which file format and video and
audio algorithm and quality values are in effect. If this flag is omitted, the
device driver might use a default value it defines.
See Also