如何使用委托方法从捕获会话中提取视频？

Question

我正在尝试了解相机在 swift 中的工作原理，所以我创建了一个简单的 viewController 设置会话、输入和输出实例，然后我开始录制，但是长度视频始终为零，AVCaptureOutput.isRunning 始终为假...这是我的代码

class cameraViewController: UIViewController, AVCaptureFileOutputRecordingDelegate {

    let recordButton: UIButton = {
        let button = UIButton()
        button.layer.cornerRadius = 30
        button.backgroundColor = UIColor.black
        button.translatesAutoresizingMaskIntoConstraints = false
        button.addTarget(self, action: #selector(startRecording), for: UIControl.Event.touchUpInside)
        return button
    }()

    let session = AVCaptureSession()
    lazy var previewLayer = AVCaptureVideoPreviewLayer(session: session)


    override func viewDidLoad() {
        super.viewDidLoad()
        previewLayer.frame = view.frame
        view.layer.addSublayer(previewLayer)
        setUpSession()
        setUpViewsAndConstraints()
    }


    func setUpViewsAndConstraints(){
        view.addSubview(recordButton)

        recordButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        recordButton.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -80).isActive = true
        recordButton.widthAnchor.constraint(equalToConstant: 60).isActive = true
        recordButton.heightAnchor.constraint(equalToConstant: 60).isActive = true


    }

    @objc func startRecording(button: UIButton){
        let url = Bundle.main.bundleURL
        let output = (session.outputs[0] as! AVCaptureMovieFileOutput)
        print(output.isRecording)

        if output.isRecording == false {
            print("recording is about to start")
            output.startRecording(to: url, recordingDelegate: self)
        } else {
            print("recording is about to stop")
            output.stopRecording()
        }
    }


    func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {
        print("recorded duration:",output.recordedDuration)
    }


    func setUpSession(){
        session.beginConfiguration()

        // setting devices and inputs

        guard let device = AVCaptureDevice.default(AVCaptureDevice.DeviceType.builtInDualCamera, for: AVMediaType.video, position: AVCaptureDevice.Position.unspecified) else {return}
        guard let input = try? AVCaptureDeviceInput(device: device) else {print("input failed");return}
        session.addInput(input)

        // setting outputs...

        let videoOutput = AVCaptureMovieFileOutput()
        session.sessionPreset = AVCaptureSession.Preset.high
        session.addOutput(videoOutput)
        session.commitConfiguration()
        session.startRunning()
    }

}

我可以在我的视图层上正常看到来自摄像头的输入视频，但是当我点击录制按钮时似乎没有任何效果，委托方法立即打印出录制的持续时间为零，并且 @objc func startRecording(button: UIButton) 永远不会打印出 "recording is about to stop" 但总是 "recording is about to start"..

我应该把哪个 url 放在方法 output.startRecording(to: url, recordingDelegate: self) 上？一旦数据进入委托方法，我有点困惑为什么我需要指定这个URL我应该放在那里什么？

我在这里错过了什么？

提前谢谢你的回答！！

Answer 1

这里

output.startRecording(to: url, recordingDelegate: self)

你应该放 url 的输出视频，因为你将它设置为

let url = Bundle.main.bundleURL

无法写入主包，因此无法开始记录，您可以通过检查打印的错误来验证

func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {
    print(error)
}

您需要在文档中创建一个 url say 并提供它

 let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0] 
 let completeMovie = URL(fileURLWithPath: documentsURL.path).appendingPathComponent("video.mp4")

如何使用委托方法从捕获会话中提取视频？

how to extract the video from the capture session using the delegate method?

ios

avcapturesession

avcapturemoviefileoutput

swift