捕捉图像SWIFT的AVCapture会话

Question

我创建了一个AVCaptureSession来捕获视频输出并通过UIView将其显示给用户。现在，我希望能够单击一个按钮(takePhoto方法)，并在UIImageView中显示来自会话的图像。我试图迭代每个设备连接，并试图保存输出，但这是行不通的。下面是我的代码

let captureSession = AVCaptureSession()
var stillImageOutput: AVCaptureStillImageOutput!

@IBOutlet var imageView: UIImageView!
@IBOutlet var cameraView: UIView!


// If we find a device we'll store it here for later use
var captureDevice : AVCaptureDevice?

override func viewDidLoad() {
    // Do any additional setup after loading the view, typically from a nib.
    super.viewDidLoad()
    println("I AM AT THE CAMERA")
    captureSession.sessionPreset = AVCaptureSessionPresetLow
    self.captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    if(captureDevice != nil){
        beginSession()
    }
}
    func beginSession() {

    self.stillImageOutput = AVCaptureStillImageOutput()
    self.captureSession.addOutput(self.stillImageOutput)
    var err : NSError? = nil
    self.captureSession.addInput(AVCaptureDeviceInput(device: self.captureDevice, error: &err))

    if err != nil {
        println("error: \(err?.localizedDescription)")
    }

    var previewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
    self.cameraView.layer.addSublayer(previewLayer)
    previewLayer?.frame = self.cameraView.layer.frame
    captureSession.startRunning()
}

@IBAction func takePhoto(sender: UIButton) {
    self.stillImageOutput.captureStillImageAsynchronouslyFromConnection(self.stillImageOutput.connectionWithMediaType(AVMediaTypeVideo)) { (buffer:CMSampleBuffer!, error:NSError!) -> Void in
        var image = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer)
        var data_image = UIImage(data: image)
        self.imageView.image = data_image
    }
}
}

Answer 1

在开始之前，应该尝试在向会话添加输入和输出时添加一个新线程。在苹果公司的文件中，他们说

重要: startRunning方法是一个阻塞调用，可能需要一些时间，因此您应该对串行队列执行会话设置，这样主队列就不会被阻塞(这将保持UI响应)。有关规范实现示例，请参见AVCam获取iOS。

尝试在create方法中使用分派，如下所示

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), { // 1
        self.captureSession.addOutput(self.stillImageOutput)
        self.captureSession.addInput(AVCaptureDeviceInput(device: self.captureDevice, error: &err))
        self.captureSession.sessionPreset = AVCaptureSessionPresetPhoto
        if err != nil {
            println("error: \(err?.localizedDescription)")
        }
        var previewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
        previewLayer?.frame = self.cameraView.layer.bounds
        previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
        dispatch_async(dispatch_get_main_queue(), { // 2
                    // 3
            self.cameraView.layer.addSublayer(previewLayer)
            self.captureSession.startRunning()
            });
        });