# mpeg compression

### Zahid Ali (view profile)

04 Jun 2006 (Updated )

Mpeg compression

motionEstES(imgP, imgI, mbSize, p)
```% Computes motion vectors using exhaustive search method
%
% Input
%   imgP : The image for which we want to find motion vectors
%   imgI : The reference image
%   mbSize : Size of the macroblock
%   p : Search parameter  (read literature to find what this means)
%
% Ouput
%   motionVect : the motion vectors for each integral macroblock in imgP
%   EScomputations: The average number of points searched for a macroblock
%
% Written by Aroh Barjatya

function motionVect = motionEstES(imgP, imgI, mbSize, p)

[row col] = size(imgI);

vectors = zeros(2,row*col/mbSize^2);
costs = ones(2*p + 1, 2*p +1) * 65537;

%computations = 0;

% we start off from the top left of the image
% we will walk in steps of mbSize
% for every marcoblock that we look at we will look for
% a close match p pixels on the left, right, top and bottom of it

mbCount = 1;
for i = 1 : mbSize : row-mbSize+1
for j = 1 : mbSize : col-mbSize+1

% the exhaustive search starts here
% we will evaluate cost for  (2p + 1) blocks vertically
% and (2p + 1) blocks horizontaly
% m is row(vertical) index
% n is col(horizontal) index
% this means we are scanning in raster order

for m = -p : p
for n = -p : p
refBlkVer = i + m;   % row/Vert co-ordinate for ref block
refBlkHor = j + n;   % col/Horizontal co-ordinate
if ( refBlkVer < 1 || refBlkVer+mbSize-1 > row ...
|| refBlkHor < 1 || refBlkHor+mbSize-1 > col)
continue;
end
imgI(refBlkVer:refBlkVer+mbSize-1, refBlkHor:refBlkHor+mbSize-1), mbSize);
%                computations = computations + 1;

end
end
%       costs
% Now we find the vector where the cost is minimum
% and store it ... this is what will be passed back.

[dx, dy, min] = minCost(costs); % finds which macroblock in imgI gave us min Cost
vectors(1,mbCount) = dy-p-1;    % row co-ordinate for the vector
vectors(2,mbCount) = dx-p-1;    % col co-ordinate for the vector
mbCount = mbCount + 1;
costs = ones(2*p + 1, 2*p +1) * 65537;
end
end

motionVect = vectors;
%EScomputations = computations/(mbCount - 1);
```