I have a UIViewController in which I use AVCaptureSession to show the camera and it is working just fine and fast. I placed a UIButton
UIViewController
AVCaptureSession
UIButton
As AVCaptureStillImageOutput is deprecated, I created another Swift example of using AVCaptureSession and AVCapturePhotoOutput in iOS 10. Check this out.
AVCaptureStillImageOutput
AVCapturePhotoOutput