How can I use the same webcam for displaying video on a gui and a function that is run with the gui. I get a error saying winvideo: The device associated with device ID 1 is already in use. A new videoinput object cannot be created ....while in use

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Richard
Richard on 26 Jun 2014
Answered: Chaitra on 26 Jun 2014
I am making a GUI and I want to display a live video on my GUI with the same webcam i use for collecting data for a function that i run with the GUI. My function uses the webcam to take a snap shot and than calculates a value that is used later in the function. I think i know whats going on but i don't know how to fix it or even if i can. I need to make something global right...but what and where. THANKS IN ADVANCE and here is the error i get.
winvideo: The device associated with device ID 1 is already in use. A new videoinput object cannot be created for this device while it is in use.

Answers (2)

David Sanchez
David Sanchez on 26 Jun 2014
Before you create the video object using videoinput function:
obj = videoinput('winvideo',1); % or something similar, I guess
declare it as global:
global obj
obj = videoinput('winvideo',1); % or something similar, I guess
Then, declare the global variable within your function, and then, use the variable, for example, taking an image.
function your_fun(inputvars)
global obj
frame = getsnapshot(obj);
I never did it, but I think it could work
  1 Comment
Richard
Richard on 26 Jun 2014
No this did not work....but now i can see live video on my GUI so that's good. I get the same error now when i try to start my function with the push button in my GUI.

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Chaitra
Chaitra on 26 Jun 2014
As you have indicated in your code:
videoinput('winvideo', 1, 'YUY2_640x480');
A new video input object is being created on the same device. This object is already created as you are accessing it via GUI. I would suggest you to use the same object handle to perform further operations.
Instead of using custom GUI, you can use Imaqtool GUI that is shipped with MATLAB.
>>imaqtool

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