How can i adjust brightness of a live video in image acquisition?

I am using the Image Acquisition Toolbox to create a simple interactive GUI that should allow the user to preview the image and dynamically adjust the brightness of the video feed.

I'm using a slider to adjust the value of brightness between(-64 to 64), code looks like this:

vid = videoinput('winvideo',1);
src = getselectedsource(vid);
preview(vid);
bri = get(handles.BrightnessSlider,'Value');
 if(bri > -65 || bri < 65 )
        stoppreview(vid);        
        src.Brightness = bri;
        preview(vid);      
end

Problem here is that brightness isn't changing when I move the slider, the value on slider does change.

Please help me solving this error. Thanks in advance.

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Walter Roberson]

MATLAB does not use {} for code blocks.

[Sanjay Yadav]

Thanks, I didn't notice that. But there is still a problem. Maybe in logic this time.