How can I tell if a frame grabber is in use by another application with Image Acquisition Toolbox?

I use my image acquisition hardware with multiple applications. I would like to be able to query the device from MATLAB to see if it is currently in use by the other application.

With one of my winvideo devices, if it is in use by another application, IMAQHWINFO returns an empty cell array when the device is in use. For example:

x=imaqhwinfo('winvideo')

returns

 x = 

 DeviceIDs: {1x0 cell}

 DeviceInfo: [1x0 struct]

This is not the case with other devices.

Answer 1

[MathWorks Support Team]

A function to determine if image acquisition hardware is in use by another application is not available in Image Acquisition Toolbox.

The behavior of the winvideo adaptor described above is not universal to all winvideo devices and can not be expected to work for other drivers or even the same winvideo device under different circumstances. In most cases, the function IMAQHWINFO still returns a device ID even when the device is in use.

To workaround this issue you can tell that a device is in use when you receive an error while attempting to access the device. For example when a device is in use and you attempt to create a video input object

v=videoinput('winvideo', 1)

you may receive the error

 ??? Cannot access information on the image acquisition device.

 One or more arguments are invalid 

 Make sure no other objects or applications are accessing the same device.

Please note that this command will not always fail, but subsequent image acquisition commands may fail with similar error messages.

available

To gracefully catch this error, you can enclose the commands in a try-catch block. For example

result = 'Try Again';

while strcmp(result,'Try Again')

      try

          v=videoinput('winvideo', 1);

          h = preview(v);

          result = 'Success';

      catch

          delete(v)

          result = questdlg(['Image acquisition device is not available.  '...

              'It may be in use by another application.'],...

              'Error Accessing Hardware','Try Again','Abort','Try Again');

      end

end