There is an offset A between green input shaft and blue output shaft.
The green shaft has an oblique pivot for pink part.
Distance between center of sphere of the pink part and rotary axis of the green shaft is B.
If B smaller than A: the blue shaft rocks.
If B larger than A: the blue shaft rotates irregularly, Transmission ratio: 1.
The video shows case when B = A. The blue shaft rotates regularly. Transmission ratio: 1/2.
The B = A mechanism has unstable position when center of the pink sphere is on the axis of the blue shaft. Inertia of the output helps overcome this position.
Purpose of yellow pins and slots on the pink part is to show that the latter does not rotate together with the green shaft. So it is possible to put a flexible tube connecting upper bearing and disk of the pink part thus to perform motion transmission through closed wall on which the upper bearing is fixed. See the sketch.