Managing Memory Usage

Freeing Memory

At times, while acquiring image data, you might want to delete some or all of the frames that are stored in memory. Using the flushdata function, you can delete all the frames currently stored in memory or only those frames associated with the execution of a trigger.

The following example illustrates how to use flushdata to delete all the frames in memory or one trigger's worth of frames.

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 five frames per trigger and, to show the effect of flushdata, configure multiple triggers using the TriggerRepeat property.
```
vid.FramesPerTrigger = 5
vid.TriggerRepeat = 2;
```
Start the image acquisition object — Call the start function to start the image acquisition object.
```
start(vid)
```
The object executes an immediate trigger, acquires five frames of data, and repeats this trigger two more times. After logging the specified number of frames, the object stops running.
To verify that the object acquired data, view the value of the FramesAvailable property. This property reports how many frames are currently stored in the memory buffer.
```
vid.FramesAvailable
ans =

   15
```
Delete a trigger's worth of image data — Call the flushdata function, specifying the mode 'triggers'. This deletes the frames associated with the oldest trigger.
```
flushdata(vid,'triggers');
```
The following figure shows the frames acquired before and after the call to flushdata. Note how flushdata deletes the frames associated with the oldest trigger.
To verify that the object deleted the frames, view the value of the FramesAvailable property.
```
vid.FramesAvailable
ans =

   10
```
Empty the entire memory buffer — Calling flushdata without specifying the mode deletes all the frames stored in memory.
```
flushdata(vid);
```
To verify that the object deleted the frames, view the value of the FramesAvailable property.
```
vid.FramesAvailable
ans =

   0
```
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
```