Background generator...

bckGenerator.m

function [ Bkg ] = bckGenerator( videoStream, sampling )    
    buffer = [];
    counter = 0;
    % start : step size : end
    for t = 1:sampling:size(videoStream, 4)
        counter = counter + 1;
        currentFrame = read(videoStream, t);
        currentFrameGrey = rgb2gray(currentFrame);
        currentFrameGrey = double(currentFrameGrey);
        buffer(:,:,counter) = currentFrameGrey;
    end
    Bkg = median(buffer, 3);
end