Crop a specific rect of video in iOS

I have a recorded video and at some point , i need to crop a specific rect of a video , so that i can view exactly what is happening in that area in details. For eg i am running the video full screen and the video is baseball match showing the action of a pitcher , is it possible to crop the throwing ball action only to a different portion of the screen and play in sync with the actual video. Does AVFoundation support this .Is there any frameworks to achieve this.