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Managing Video Input Objects

This example shows how to find video input objects and remove video input objects from memory.

Finding Video Input Objects in Memory

To find video input objects in memory, use the IMAQFIND function. IMAQFIND returns an array of video input objects.

objects = imaqfind
objects =

     []

% Create video input objects.
vidobj1 = videoinput('matrox', 1, 'M_CCIR');
vidobj2 = videoinput('matrox', 1, 'M_PAL_RGB');
vidobj3 = videoinput('matrox', 1, 'M_NTSC_RGB');

% Find all valid objects.
objects = imaqfind
   Video Input Object Array:

   Index:   Type:          Name:  
   1        videoinput     M_CCIR-matrox-1
   2        videoinput     M_PAL_RGB-matrox-1
   3        videoinput     M_NTSC_RGB-matrox-1
   	

Removing Objects From Memory

To delete a video input object from memory, use the DELETE function with the object.

% Delete the first object in the array.
delete(objects(1))

Find all remaining valid objects.

objects = imaqfind
   Video Input Object Array:
	 
   Index:   Type:          Name:  
   1        videoinput     M_PAL_RGB-matrox-1
   2        videoinput     M_NTSC_RGB-matrox-1

Using the DELETE function with the object will remove the object from memory but not from the MATLAB® workspace. To remove an object from the MATLAB workspace use the CLEAR function. To see what objects are in the MATLAB workspace, use the WHOS function.

% Display the current workspace.
whos
   Name          Size                   Bytes  Class

   objects       1x2                     1200  videoinput object
   vidobj1       1x1                     1060  videoinput object
   vidobj2       1x1                     1060  videoinput object
   vidobj3       1x1                     1060  videoinput object
  
Grand total is 185 elements using 4380 bytes

Since an object was deleted, it is no longer valid.

vidobj1
Invalid Image Acquisition object.
This object is not associated with any hardware and
should be removed from your workspace using CLEAR.

Clear the associated variable.

clear vidobj1

Display the current workspace.

whos
  Name          Size                   Bytes  Class

  objects       1x2                     1200  videoinput object
  vidobj2       1x1                     1060  videoinput object
  vidobj3       1x1                     1060  videoinput object

Grand total is 142 elements using 3320 bytes

To remove all video input objects from memory and to reset the toolbox to its initial state, use the IMAQRESET function.

Note: Using the IMAQRESET function will only delete objects from memory, not clear them from the MATLAB workspace.

imaqreset

Verify no objects remain.

objects = imaqfind
objects =

     []

Variables associated with deleted objects still remain.

whos
   Name          Size                   Bytes  Class

  objects       0x0                        0  double array
  vidobj2       1x1                     1060  videoinput object
  vidobj3       1x1                     1060  videoinput object

Grand total is 86 elements using 2120 bytes

Clear any remaining variables associated with deleted objects.

clear vidobj2 vidobj3

See also IMAQFIND, IMAQDEVICE/DELETE, IMAQ/PRIVATE/CLEAR, IMAQDEVICE/ISVALID.

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