How to take a screenshot from an video playing through MPMediaPlayerController

ViewController.swift

import UIKit
import MediaPlayer

class ViewController: UIViewController {
    
    var moviePlayer: MPMoviePlayerController?
     var playButton: UIButton!
    
    func videoHasFinishedPlaying(notification: NSNotification){
        
        print("Video finished playing")
        
        let reason =
        notification.userInfo![MPMoviePlayerPlaybackDidFinishReasonUserInfoKey]
            as! NSNumber?
        
        if let theReason = reason{
            
            let reasonValue = MPMovieFinishReason(rawValue: theReason.integerValue)
            
            switch reasonValue!{
            case .PlaybackEnded:
                /* The movie ended normally */
                print("Playback Ended")
            case .PlaybackError:
                /* An error happened and the movie ended */
                print("Error happened")
            case .UserExited:
                /* The user exited the player */
                print("User exited")
            }
            
            print("Finish Reason = \(theReason)")
            stopPlayingVideo()
        }
        
    }
    
    func image(image: UIImage, didFinishSavingWithError error: NSError?, contextInfo:UnsafePointer<Void>) {
        if error == nil {
            println("Your altered image has been saved to your photos.")
        } else {
            println("Save error: \( error?.localizedDescription)")
        }
    }
    
    func stopPlayingVideo() {
        
        if let player = moviePlayer{
            NSNotificationCenter.defaultCenter().removeObserver(self)
            player.stop()
            player.view.removeFromSuperview()
        }
        
    }
    
    func videoThumbnailIsAvailable(notification: NSNotification){
        
        if let _ = moviePlayer{
            println("Thumbnail is available")
            
            let thumbnail =
            notification.userInfo![MPMoviePlayerThumbnailImageKey] as? UIImage
            
            if let image = thumbnail{
                
                println("Thumbnail image = \(image)")
                UIImageWriteToSavedPhotosAlbum(image, self, "image:didFinishSavingWithError:contextInfo:", nil)
                
            }
        }
        
    }
    
    func startPlayingVideo(){
        
         let mainBundle = NSBundle.mainBundle()
        
        let url = NSURL(string: "http://www.sample-videos.com/video/mp4/720/big_buck_bunny_720p_5mb.mp4")
        
        if let _ = moviePlayer{
            stopPlayingVideo()
        }
        
        moviePlayer = MPMoviePlayerController(contentURL: url)
        
        if let player = moviePlayer{
            
            NSNotificationCenter.defaultCenter().addObserver(self,
                selector: "videoHasFinishedPlaying:",
                name: MPMoviePlayerPlaybackDidFinishNotification,
                object: nil)
            
            NSNotificationCenter.defaultCenter().addObserver(self,
                selector: "videoThumbnailIsAvailable:",
                name: MPMoviePlayerThumbnailImageRequestDidFinishNotification,
                object: nil)
            
            print("Successfully instantiated the movie player")
            
            player.scalingMode = .AspectFit
            
            view.addSubview(player.view)
            
            player.setFullscreen(true, animated: true)
            
            player.play()
            
            let thirdSecondThumbnail = 16.0
            
            player.requestThumbnailImagesAtTimes([thirdSecondThumbnail],
                timeOption: .NearestKeyFrame)
            
        } else {
            print("Failed to instantiate the movie player")
        }
        
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
           playButton = UIButton(frame: CGRectMake(0, 0, 77, 77))
           playButton.setTitle("Play", forState: UIControlState.Normal)
           playButton.titleColorForState(UIControlState.Normal)
           playButton.layer.cornerRadius = 7
           playButton.backgroundColor = UIColor.redColor()
           playButton.center = self.view.center
           self.view.addSubview(playButton)
        
           playButton.addTarget(self,
                action: "startPlayingVideo",
                forControlEvents: .TouchUpInside)
            
        
    }
    
}