my code can't preview webcam

% Create video input object. 
vid = videoinput('winvideo',2, 'I420_1504x832');

% Set video input object properties for this application.
vid.TriggerRepeat = 100;
vid.FrameGrabInterval = 5;

% Set value of a video source object property.
vid_src = getselectedsource(vid);
vid_src.Tag = 'motion detection setup';

% Create a figure window.
figure

% Start acquiring frames.
start(vid)

% Calculate difference image and display it.
while(vid.FramesAvailable >= 2)
    data = getdata(vid,2); 
    diff_im = imabsdiff(data(:,:,:,1),data(:,:,:,2));
    imshow(diff_im);
    drawnow     % update figure window
end

stop(vid)

please check in my code

[Walter Roberson]

That code looks reasonable for the situation in which you want to acquire 100 frames first and then process them when you have all 100.