Double Inverse Parallelogram.

A second similar inverse parallelogram is connected to the first. Similar ratio is 2.

The long bars of the first (big) are the ground bar and the green bar.

The long bars of the second (small) are the blue bar and the left pink crank.

The pink cranks turn in opposite directions with the same velocity.

This mechanism acts as a spur gear drive (in glass, added for illustration), each gear is fixed to the pink crank. Measure for overcoming dead points is not shown.