User`s guide

Creating Image Acquisition Objects

5-11

The Trigger Parameters section lists the trigger type configured for the object and

the number of times the trigger is to be executed. Trigger execution initiates data

logging, and the toolbox supports several types of triggers. The example object

is configured by default with an immediate trigger. For more information about

configuring triggers, see “Specifying the Trigger Type” on page 6-8.

The Status section lists the current state of the object. A video input object can be in

one of several states:

• Running or not running (stopped)

• Logging or not logging

• Previewing or not previewing

In the example, the object describes its state as Waiting for START. This indicates

it is not running. For more information about the running state, see “Starting and

Stopping a Video Input Object” on page 5-22. This section also reports how

many frames of data have been acquired and how many frames are available in the

buffer where the toolbox stores acquired frames. For more information about these

parameters, see “Controlling Logging Parameters” on page 6-24.

Specifying the Video Format

You can optionally specify the format of the video stream when you create a video input

object as a third argument to the videoinput function. This argument can take two

forms:

• A text string specifying a video format

• A name of a device configuration file, also known as a camera file

The following sections describe these options. If you do not specify a video format, the

videoinput function uses one of the video formats supported by the device. For Matrox

and Data Translation

devices, it chooses the RS170 video format. For Windows devices,

it uses the first RGB format in the list of supported formats or, if no RGB formats are

supported, the device's default format.

Using a Video Format String

To specify a video format as a text string, use the imaqhwinfo function to determine

the list of supported formats. The imaqhwinfo function returns this information in

the SupportedFormats field of the device information structure. See “Determining

Supported Video Formats” on page 5-5 for more information.