when i use this code matlab even hangs or give me constant blue screen any ideas ?

if true
clear all
clc
cd c:\try
a=0;
obj = videoinput('winvideo', 1);
preview(obj);
frame =rgb2gray(getsnapshot(obj));
while a<1
% for i = 1:1000
frame1 = rgb2gray(getsnapshot(obj));
x= frame-frame1; 
border = edge(x,'canny');
image(border);
end

end

Answer 1

[Image Analyst]

Step through it with the debugger. Which line causes the problems?

Answer 2

[Walter Roberson]

You never change "a" so it will always be less than 1.

Also you should add

drawnow()

after the image() call.