swift - 不使用 setSampleBufferDelegate 调用 captureOutput 函数

Question

我开始开发 iOS 应用程序，这是我的第一篇 SO 帖子。我正在尝试实现一个 UI View ，它可以显示后置摄像头的预览视频并处理捕获的帧。我的预览层工作得很好，我可以在我的 UI View 中看到图片显示。但是，从未调用 captureOutput 函数。

我在网上搜索类似的问题和解决方案有一段时间了，并尝试调整不同的东西，包括输出、连接和调度队列设置，但都没有奏效。任何人都可以帮助我或分享一些见解和方向吗？非常感谢!

这是我的代码，我使用 Xcode 11 beta 和 iOS 10 作为构建目标。

class ThreeDScanningViewController: UIViewController, 
AVCaptureVideoDataOutputSampleBufferDelegate {

    @IBOutlet weak var imageView: UIImageView!

    var session : AVCaptureSession!
    var device : AVCaptureDevice!
    var output : AVCaptureVideoDataOutput!
    var previewLayer : AVCaptureVideoPreviewLayer!

    override func viewDidLoad() {
        super.viewDidLoad()
                //NotificationCenter.default.addObserver(self, selector: #selector(self.startedNotif), name: NSNotification.name.CaptureSessionDidStartRunningNotification, object: nil)

    func initCamera() -> Bool {
        session = AVCaptureSession()
        session.sessionPreset = AVCaptureSession.Preset.medium

        let devices = AVCaptureDevice.devices()

        for d in devices { 
            if ((d as AnyObject).position == AVCaptureDevice.Position.back) {
                device = d as! AVCaptureDevice
            }
        }
        if device == nil {
            return false
        }

        do {
            // Set up the input

            let input : AVCaptureDeviceInput!
            try input = AVCaptureDeviceInput(device: device)

            if session.canAddInput(input) {
                session.addInput(input)
            } else {
                return false
            }

            // Set up the device

            try device.lockForConfiguration()
            device.activeVideoMinFrameDuration = CMTimeMake(1, 15)
            device.unlockForConfiguration()

            // Set up the preview layer

            previewLayer = AVCaptureVideoPreviewLayer(session: session)
            previewLayer.frame = imageView.bounds
            imageView.layer.addSublayer(previewLayer)

            // Set up the output

            output = AVCaptureVideoDataOutput()
            output.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString) as String: kCVPixelFormatType_32BGRA]

            let queue = DispatchQueue(label: "myqueue")
            output!.setSampleBufferDelegate(self, queue: queue)

            output.alwaysDiscardsLateVideoFrames = true

            if session.canAddOutput(output) {
                session.addOutput(output)
            } else {
                return false
            }

            for connection in output.connections {
                if let conn = connection as? AVCaptureConnection {
                    if conn.isVideoOrientationSupported {
                        conn.videoOrientation = AVCaptureVideoOrientation.portrait
                    }
                }
            }

            session.startRunning()

        } catch let error as NSError {
            print(error)
            return false
        }

        return true
    }

    func captureOutput (captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
        print("captureOutput!\n");
        DispatchQueue.main.async(execute: {
            // Do stuff
        })
    }
}

以下是我查看过的一些链接，但没有一个与解决我的问题相关:

• AVCaptureVideoDataOutput captureOutput not being called

• ios capturing image using AVFramework

• AVCaptureDeviceOutput not calling delegate method captureOutput

• iOS: captureOutput:didOutputSampleBuffer:fromConnection is NOT called

• didOutputSampleBuffer delegate not called

Answer 1

我终于找到了问题的原因。您需要确保为 Swift 3 语法的 captureOutput 函数使用正确的函数签名。

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection)

不

func captureOutput(_ output: AVCaptureOutput, didOutputSampleBuffer sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection)

我使用的是旧版本的 Swift 语法，编译器没有警告我这个问题!更正函数签名后，captureOutput 函数被漂亮地调用了:-)