Input is the case with pulley of n1 constant velocity. Output are the orange and green identical gear shafts of n2 and n3 velocities. The yellow and blue satellite gears have the same tooth number.
The video shows when the orange shaft slows down, the green one speeds up and vice versa to maintain the equation n1 = (n2 + n3)/2.
The satellite gears turn around their own axles only when n2 or n3 differs from n1.