How to play a video slowly for marking

I am Creating application for coaching. I struck with the marking on video. So I choose ffmpeg for converting video to image frame. That make me time delay as well as memory issues. I need to provide the user play the video slowly as frame by frame. Is there any other way to do that with out image conversion. V1 Golf did that process very qui开发者_开发技巧ck manner. Please help me.

I would try converting video frame in separate thread and I would extract a few frames ahead as images in the background when user gets into 'slow motion mode'. Here is example for one frame, so you should be quick with others: Video frame capture by NSOperation. This should reduce delays and frames could be converted while user is eye-consuming subsequent frames.