Recommended.

Does what it does, and does it well. Is the only app I found that allows easy stepping backwards through movies by frame. (Many allow stepping forwards by frame.) The interface collects your stills and then lets you export them as a group, works well. I tried QT 7 Pro, QT X, VLC, MPEG Streamclip — all good, but none as good as SnapMotion for quickly extracting stills from video.

I have run it on MP4 files up to 1.3 GB with no problems at all.

If you need to extract high-quality stills from video, and you need frame-by-frame control, get it.

Consummate1 about SnapMotion : Easily extract images from video