User`s guide

4 Connecting to Hardware
At any one time, only one of the video source objects, called the selected
source, can be active. This is the source used for acquisition. The toolbox
selects on e of th e video source objects by default, but you can change this
selection. See “Specify ing the Selected Video Source Object” on page 4-15
for more information.
The follow in g fi gure illustrates how a video in put object acts as a co ntainer
for one or more video source objects.
Relationship of Video Input Objects and Video Source Objects
For example, a Matrox frame grabber device can support eight physical
connections, which M atrox calls channels. These channels can be configured in
various ways, depending upon the video format. If you specify a monochrome
video format, such as RS170, the to olbox creates eight video source obje cts,
one object for each o f the eight channels on the device. If you specify a color
video format, such as NTSC RGB, the Matrox device uses three physical
channels to represent one RGB connection, where each physical connection
provides the red data, green data, and blue data separately. With this format,
the toolbox only creates two video source objects for the same device.
Creating a Video Input Object
To create a video input object, call the videoinput function specifying the
adaptor name, de vice ID, and video format. You retrieved this information
using the
imaqhwinfo function (described in “Getting Hardware Information”
on page 4-3). The only required argument is the adaptor name. The toolbox
can u se default values for the device ID and video format.
This example creates a video input objecttorepresenttheconnectiontoa
Matrox image acquisition device. The
imaqhwinfo function includes the
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