Does the trick ( and for free)

Of course quality drops when slows down but thats to be expected - but it works for learning things that are on video but moving too fast and you can adjust speed... For free!
("Doesnt do what I want..." is not a review... Why do people write this and rate an app low? It also wont fry an egg!)

Mbiriviri about Slowmo - SlowMo Video Analysis