User`s guide

6 Acquiring Image Data

6-28

100

Clean up Always remove image acquisition objects from memory, and the variables

that reference them, when you no longer need them.

delete(vid)

clear vid

Determining How Many Frames Are Available

The FramesAcquired property tells how many frames the object has logged since it was

started, described in “Determining How Much Data Has Been Logged” on page 6-26.

Once you move frames from the memory buffer into the MATLAB workspace, the number

of frames stored in the memory buffer will differ from the FramesAcquired value. To

determine how many frames are currently available in the memory buffer, check the

value of the FramesAvailable property.

Note The FramesAvailable property tells the number of frames in the memory buffer,

not in the disk log, if LoggingMode is configured to 'disk' or 'disk&memory'. Because

it takes longer to write frames to a disk file than to memory, the number of frames stored

in the disk log might lag behind those stored in the memory buffer. To see how many

frames are available in the disk log, look at the value of the DiskLoggerFrameCount

property. See “Logging Image Data to Disk” on page 6-42 for more information.

This example illustrates the distinction between the FramesAcquired and the

FramesAvailable properties:

Create an image acquisition object — This example creates a video input object

for a Windows image acquisition device. To run this example on your system, use the

imaqhwinfo function to get the object constructor for your image acquisition device

and substitute that syntax for the following code.

vid = videoinput('winvideo',1);

Configure properties — For this example, configure an acquisition of 15 frames.

vid.FramesPerTrigger = 15

Start the image acquisition object — Call the start function to start the image

acquisition object.