problem with real time detection

i made a motion detection code :

clear all

threshold= 35;

video= mmreader('SampleVideo.avi'); first_frame = video.read(1);

 first_frame_gray=rgb2gray(first_frame);

 total_frames= video.NumberOfFrames;

 [row,column,page]=size(first_frame);
 dummy_matrix = zeros(row,column);

for i=2:total_frames

    current_frame=video.read(i);

     current_frame_gray=rgb2gray(current_frame);

     frame_difference=imabsdiff(current_frame_gray,first_frame_gray);

    for nr=1:row                 

        for nc=1:column

            if ((frame_difference(nr,nc) > threshold))          

                dummy_matrix(nr,nc) = frame_difference(nr,nc);

            else

                dummy_matrix(nr,nc) = 0;   
            end

        end

    end
    first_frame_gray=  current_frame_gray;

    figure(1)
    subplot(2,1,1)

    imshow(current_frame)

    subplot(2,1,2)

imshow(uint8(dummy_matrix))

end
.........................................
now i convert it to real time  here is my code for real time:

clear all;

threshold=35; i=1;

video = videoinput('winvideo',1,'YUY2_1280x1024'); first_frame=getsnapshot(video); first_frame_gray=rgb2gray(first_frame);

[row,column,page]=size(first_frame); dummy_matrix = zeros(row,column);

current_frame=getsnapshot(video);
current_frame_gray = rgb2gray(current_frame);     
frame_difference=imabsdiff(current_frame_gray,first_frame_gray);

 for nr=1:row        
        for nc=1:column            
            if (frame_difference(nr,nc) > threshold)          
                dummy_matrix(nr,nc) = frame_difference(nr,nc);                            
            else               
                dummy_matrix(nr,nc) = 0;   
            end            
        end        
    end

    first_frame_gray=  current_frame_gray;

    preview(video);
      figure(1)
    subplot(2,1,1)
    imshow(current_frame)        
    subplot(2,1,2)    
    imshow(uint8(dummy_matrix))

     Movie(i)  = im2frame(uint8(dummy_matrix),gray);           
    i=i+1;

the problem is my code run once and capture only first frame . if i use while loop then the code rune forever and to stop it i have to close matlab plus its really slow.

Answer 1

[Image Analyst]

First of all, binarize that pair of for loops like this

binaryImage = frame_difference(nr,nc) <= threshold;
dummy_matrix = frame_difference;
dummy_matrix(binaryImage) = 0;

anyway, I see no other looping in your code. Why do you think it should loop? You have no for or while construction to make it loop. You need to put in code to make it loop if you want it to loop.