% medemo.m - motion estimation demonstration
% (C) 2006 by Yu Hen Hu
% created: 12/20/2006
% step by step motion estimation using 4 x 4 macro block over 
% a 16 x 16 reference frame
% cur: current block 4 x 4
% ref: reference frame: 16 x 16

clear all; close all
load medemo.mat; % contains ref and cur

echo on
% assume the 4 x 4 current block cur is located at (2, 2) block position 
% of the 16 x 16 current frame. 
% Thus, the origin in the reference frame is the (5, 5) pixel locations
% The search range is +- 2 pixels in each direction. 
% full block motion estimation is to be performed
% Note that the matrix indices start at 1 rather than 0 or negative integers,
% so we use sad(m+3,n+3) instead of sad(m,n)

echo off

sadmin=inf; MV=[0 0];
for m=-2:2,
   for n=-2:2,
      sad(m+3,n+3)=sum(sum(abs(cur-ref(5+m:8+m,5+n:8+n))));
      if sad(m+3,n+3)< sadmin,
         MV=[m n]; sadmin=sad(m+3,n+3);
      end
   end % n loop
end % m-loop

disp(['Sad value for (m,n) in [-2:2, -2:2]: ']);
disp(sad)
disp(['Min sad value = ' num2str(sadmin) ', MV = [' ...
      int2str([m n]) ']']);