User`s guide

6 Acquiring Image Data

6-48

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Configure properties of the AVI file object — You can optionally configure the

properties of the AVI file object. The AVI file object supports properties that control

the data compression used, image quality, and other characteristics of the file. The

example sets the quality property to a midlevel value. By lowering the quality, the

AVI file object creates smaller log files.

aviobj.Quality = 50;

Because this example acquires image data in grayscale format (RS170), you must

also specify the colormap used with the AVI object to ensure that the stored data

displays correctly.

aviobj.Colormap = gray(256);

Create a video input object — This example creates a video input object for a

Matrox image acquisition device, using the default video format M_RS170. To run

this example on your system, use the imaqhwinfo function to get the video input

object constructor for your image acquisition device and substitute that syntax for

the following code.

vid = videoinput('matrox',1);

Configure video input object properties — Set up disk logging by setting the

value of the DiskLogger property to be aviobj, the AVI file object created in step 1.

Then, set the LoggingMode property to 'disk' (or 'disk&memory'). This example

also sets the TriggerRepeat property.

vid.LoggingMode = 'disk&memory';

vid.DiskLogger = aviobj;

vid.TriggerRepeat = 3;

Start the video input object — Start logging data to disk.

start(vid)

The object executes an immediate trigger, acquires frames of data, repeats the

trigger three additional times, and then stops.

To verify that all the frames have been logged to the AVI file, check the value of the

DiskLoggerFrameCount property. This property tells the number of frames that

have been logged to disk.

vid.DiskLoggerFrameCount