MATLAB: How Input Web Cam Real Time Live Video Record

Hi,
I have trying to record real time video from input web cam video.Below step's i have followed ,but i cannot get proper?
Step 1 : When I have Click Button Start Button ,input web cam on
    if true
  faceDetector = vision.CascadeObjectDetector('FrontalFaceCART');
      if strcmp(get(handles.captureImage,'String'),'Start Training')
    set(handles.captureImage,'String','Stop Training');
  vid = videoinput('winvideo');
  set(vid,'FramesPerTrigger',1);
  set(vid,'TriggerRepeat',Inf);
  set(vid,'ReturnedColorSpace','rgb');
  triggerconfig(vid, 'Manual'); 
  start(vid);
  trigger(vid); 
  I = (getdata(vid,1,'uint8'));
else
 set(handles.captureImage,'String','Start Training')
    stop(vid);
 delete(vid);  
end
  end
Step 2 : When i have click start Button i am getting error like : *Image acquisition object OBJ is an invalid object.Error in GUI>captureImage_Callback (line 400)
    stop(vid);*
Step 3:I got  Another Error like : *Reference to a cleared variable I.
Error in GUI>captureImage_Callback (line 384)
         imshow(I);*
Note : Where i have made mistaken in Start /Stop record Button.
Thanks

Best Answer

The video object is local to the function you have it in, and is getting destroyed when the callback returns. You need to retain the object somehow, such as storing it in the handles structure.
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