Swift从照片库中获取视频的NSData

我使用UI ImagePickerController从我的库中选择一个视频.我需要提取我的视频文件的NSData.我使用以下操作从我的库中选择一个视频,但我的数据似乎是零,但我的AVPlayer播放结果NSURL中的视频,所以我知道问题不在于NSURL.如何提取所选视频文件的NSData？

func imagePickerController(picker: UIImagePickerController,didFinishPickingMediaWithInfo info: [String : AnyObject]) {
    let fileURL = info[UIImagePickerControllerReferenceURL] as! NSURL!

    let data = NSData(contentsOfURL: fileURL)
    print(data)

    player = AVPlayer(URL: fileURL)
    let playerLayer = AVPlayerLayer(player: player)
    playerLayer.frame = CGRectMake(0,300,300)
    self.view.layer.addSublayer(playerLayer)
    player.play()

    self.dismissViewControllerAnimated(true,completion: nil)
}