freeze
The freeze
command freezes video input or video output on a VCR or disables video
acquisition to the frame buffer. Digital-video, video-overlay, and VCR devices
recognize this command.
wsprintf(lpstrCommand, "freeze %s %s %s",
lpszDeviceID, lpszFreezeFlags,
lpszFlags);
Parameters
lpszDeviceID
Identifier of
an MCI device. This identifier or alias is assigned when the device is opened.
lpszFreezeFlags
Flag that
identifies what to freeze. The following table lists device types that
recognize the freeze command and the flags used by each type:
|
digitalvideo |
at rectangle |
outside |
|
overlay |
at rectangle |
|
|
vcr |
field |
input |
The following
table lists the flags that can be specified in the lpszFreezeFlags
parameter and their meanings:
|
at rectangle |
Specifies
the region that will be frozen. For video-overlay devices, this region will
have video acquisition disabled. For digital-video devices, the pixels within
the rectangle will have their lock mask bit turned on (unless the outside
flag is specified). The rectangle is relative to the video buffer origin and
is specified as X1 Y1 X2 Y2. The coordinates X1 Y1 specify the
upper left corner of the rectangle, and the coordinates X2 Y2 specify
the width and height. |
|
field |
Freezes the
first field. Field is assumed by default (if neither frame nor field is
specified). |
|
frame |
Freezes the
entire frame, displaying both fields. |
|
input |
Freezes the
current frame of the input image, whether it is paused or running. |
|
output |
Freezes the
current frame of the output from the VCR. If the VCR is playing when freeze
is issued, the current frame is frozen and the VCR is paused. If the VCR is
paused when this command is issued, the current frame is frozen. The frozen
image remains on the output device until an unfreeze command is issued. If
neither input nor output is specified, output is assumed. |
|
outside |
Indicates
that the area outside the region specified using the at flag is frozen. |
lpszFlags
Can be
wait , notify , or both. For digital-video and VCR devices, test can also
be specified. For more information about these flags, see The Wait, Notify,
and Test Flags.
Return Values
Returns zero
if successful or an error otherwise.
Remarks
When used
with VCR devices, this command is intended for frame-grabbing cards.
To specify
irregular acquisition regions with the at flag, use a series of freeze
and unfreeze
commands. Some video-overlay devices limit the complexity of the acquisition
region.
This command
is supported only if a call to the capability14PJB2D command with the can freeze flag
returns TRUE.
The following
command disables video acquisition in a 100-pixel square at the upper left
corner of the video buffer:
freeze vboard at 0 0 100 100
See Also