Create an imovie-like frame with a pinch / zoom

Question

Does anyone know how an apple created a filmstrip from frame by frame from a video? I would like to implement similar functionality by showing a frame every 5 seconds or so, with the ability to scale / scale, which either increases the resolution (frame every 1 second) or decreases it (frame every 10 seconds).

Screenshot of what I mean here;

I was looking for the framework of AVFoundation and MediaPlayer, but didn't come up with anything .. do they use the internal api or something else?

If anyone has code samples that they can use, this iOS newbie will be grateful!