Three-Frame Differencing (TFD) is applied in real time, it performs an AND operation on two pictures, one is the difference picture between I(t) and I(t-N), and the other is the difference picture between I(t-N) and I(t-2N).

I can write TFD algorithm without using SFD(N).

B(0) = I(0)

looptime t<2N

B(t) = I(t)

looptime t >= 2N

I(t) = next frame

diff1 = abs[B(t-N) - I(t)]

diff2 = abs[B(t-2N) - I(t-N)]

m1(t) = treshold(diff1,)

m2(t) = treshold(diff2,)

m(t) = AND[m1(t),m2(t)]

B(t) = I(t)

end loop

Question:How can i write pseudo-code of the TFD algorithm with using SFD(N) ?