You can specify properties at the time of object creation, or they can be specified and changed after the object is created.
Properties that can be used with the VideoDevice System object™ include:
| Property | Description |
|---|---|
Device | Device from which to acquire images. Specify
the image acquisition device to use to acquire a frame. It consists
of the device name, adaptor, and device ID. The default device is
the first device returned by obj.Device shows
the list of available devices for VideoDevice System object, |
VideoFormat | Video format to be used by the image acquisition device. Specify
the video format to use while acquiring the frame. The default value
of obj.VideoFormat shows the list of available video formats. |
DeviceFile | Name of file specifying video format. This property is only
visible when VideoFormat is set to 'From
device file'. |
DeviceProperties | Object containing properties specific to the image acquisition
device.obj.DeviceProperties.<property_name> =
<property_value>shows a device-specific
property for VideoDevice System object, |
ROI | Region-of-interest for acquisition. This is set to the
default ROI value for the specified device, which is the maximum resolution
possible for the specified format. You can change the value to change
the size of the captured image. The format is 1-based, that is, it
is specified in pixels in a 1-by-4 element vector Note that this differs from the |
HardwareTriggering | Turn hardware triggering on/off. Set this property to 'on' to
enable hardware triggering to acquire images. The property is visible
only when the device supports hardware triggering. |
TriggerConfiguration | Specifies the trigger source and trigger condition before acquisition.
The triggering condition must be met via the trigger source before
a frame is acquired. This property is visible only when HardwareTriggering is
set to 'on'. obj.TriggerConfiguration shows the list of available hardware trigger configurations. |
ReturnedColorSpace | Specify the color space of the returned image. The default
value of the property depends on the device and the video format selected.
Possible values are {rgb|grayscale|YCbCr}
when the default returned color space for the device is not grayscale.
Possible values are {rgb|grayscale|YCbCr|bayer}
when the default returned color space for the device is grayscaleobj.ReturnedColorSpace shows the list of available color space settings. |
BayerSensorAlignment | Character vector indicating the 2x2 sensor alignment. Specifies
Bayer patterns returned by hardware. Specify the sensor alignment
for Bayer demosaicing. The default value of this property is 'grbg'.
Possible values are {grbg|gbrg|rggb|bggr}.
Visible only if ReturnedColorSpace is set to 'bayer'.obj.BayerSensorAlignment shows the list of available sensor alignments. |
ReturnedDataType | The returned data type of the acquired frame. The default ReturnedDataType is single.obj.ReturnedDataType shows the list of available data types. |
ReadAllFrames | Specify whether to read one image frame or all available frames. Set
to 'on' to capture all available image frames. When
set to the default of 'off', the system object takes
a snapshot of one frame, which is the equivalent of the
getsnapshot function in the toolbox. When the
option is on, all available image frames are captured, which is the
equivalent of the getdata function in the
toolbox. |
Note
The setting of properties for the System object supports tab completion for enumerated properties while coding in MATLAB. Using the tab completion is an easy way to see available property values. After you type the property name, type a comma, then a space, then the first quote mark for the value, then hit tab to see the possible values.
Once you have created a VideoDevice System object, you can set either object-level properties or device-specific properties on it.
To set an object-level property, use this syntax:
vidobj.ReturnedColorSpace = 'grayscale';
You can see that the syntax for setting an object-level property
is to use <object_name>.<property_name> = <property_value>,
where the value may be a character vector or a numeric.
Another example of an object-level property is setting the region-of-interest,
or ROI, to change the dimensions of the acquired
image. The ROI format is specified in pixels in a 1-by-4 element vector [x
y width height].
vidobj.ROI = [1 1 200 200];
Note
This ROI value is 1-based. This differs from the videoinput object,
the Image Acquisition Tool, and the From Video Device block, all of
which are 0-based.
To set a device-specific property, use this syntax:
vidobj.DeviceProperties.Brightness = 150;
You can see that the syntax for setting a device-specific property
is to use dot notation with the object name, the DeviceProperties object,
and the property name and then make it equal to the property value.
Another example of a device-specific property is setting the frame rate for a device that supports it.
vidobj.DeviceProperties.FrameRate = '30';
Note
Once you have done a step, in order to change a property or
set a new one, you need to release the object using the release function,
before setting the new property.