how to use the previous frame of a video in a loop without saving it

hello,

I am trying to compute the silhoutte motion image from a silhouette of video, i want to perform all the steps in a sequence with saving the silhouette and then working on it. as my application is real-time

i used this code to extract the silhouette

v = VideoReader('2.mp4');
nFrames = v.NumberOfFrames;
 for f=1:nFrames              
 I=read(v,f);   
 if f==1    
     Background=I;    
     Fg=abs(I-Background);
 else
     Fg=abs(I-Background); 
 end
 grayImage = rgb2gray(abs(im2double(Fg))); % Convert to gray level
 thresholdLevel = graythresh(grayImage);
 binaryImage = im2bw(grayImage,thresholdLevel); 
% now for the silhouette motion image i have to compute 
for n=1:f
     if f==1
       smi1=binaryImage;
     else
     smi1=abs(binaryImage+binaryImage(previous frame i.e (f-1));
     end
 end
 smii=abs(smi1-bi);

my question is how do i access the previous frame within the loop, without saving it

[KSSV]

Where you are reading the frame...there you use your calculation....simple.

[Saba Baloch]

Thanks for your response, but i want to work on the already processed frame, how do i use a frame that has already been processed