title: How to overlay one video on another in iOS?
body: <p>I am trying to crop an already taken video into a circle in iOS. How might I go about doing this. I know how I would do it with AVCaptureSession but I don't know to pass in an already taken video as an AVCaptureDevice? Is there a way to crop a video into a circle. I want to overlay it on top of another video so it has to have a transparent background as well. Thanks.</p>