User`s guide

Creating and Executing Callback Functions

8-17

delete(vid)

clear vid

Monitoring Memory Usage

This example creates a callback function for a timer event that displays the toolbox's

current memory usage and stops the acquisition when the available memory for frame

storage falls below a specified amount.

Creating the Memory Monitor Callback Function

This callback function implements a simple memory usage monitoring function. The

callback function uses the imaqmem function to retrieve two memory usage statistics,

FrameMemoryLimit and FrameMemoryUsed, and then calculates the amount of memory

that is currently left for allocating frames. When the amount of memory available falls

below a specified value, the function outputs a message and stops the object.

function mem_mon(obj,event)

out = imaqmem;

mem_left = out.FrameMemoryLimit - out.FrameMemoryUsed;

msg = 'Memory left for frames';

msg2 = 'Memory load';

low_limit = 2000000;

if(mem_left > low_limit)

sprintf('%s: %d \n%s: %d',msg, mem_left,msg2, out.MemoryLoad)

else

disp('Memory available for frames getting low.');

disp('Stopping acquisition.')

stop(obj);

end

Running the Example

The example acquires frames until the amount of memory left for frame storage reaches

a lower limit specified in the callback function.

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

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