AVFoundation会话问题

Question

我正在开发一个需要录制视频的应用程序，我找到了一个由appcoda编写的帮助类，这里有一个指向github https://github.com/appcoda/FullScreenCamera的链接，但我遇到的问题是，当我运行它时，我在控制台中出现了一个错误，上面写着noCamerasAvailable，然后是captureSessionIsMissing，我还被用来改进代码，我只是不知道为什么。下面是助手类

class CameraHelper: NSObject {
    var captureSession: AVCaptureSession?

    var currentCameraPosition: CameraPosition?

    var frontCamera: AVCaptureDevice?
    var frontCameraInput: AVCaptureDeviceInput?

    var photoOutput: AVCapturePhotoOutput?

    var rearCamera: AVCaptureDevice?
    var rearCameraInput: AVCaptureDeviceInput?

    var previewLayer: AVCaptureVideoPreviewLayer?

    var flashMode = AVCaptureDevice.FlashMode.off
    var photoCaptureCompletionBlock: ((UIImage?, Error?) -> Void)?
}

extension CameraHelper {
    func prepare(completionHandler: @escaping (Error?) -> Void) {
        func createCaptureSession() {
            self.captureSession = AVCaptureSession()
        }

        func configureCaptureDevices() throws {

            let session = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInDualCamera], mediaType: AVMediaType.video, position: .unspecified)

            let cameras = session.devices.compactMap { $0 }
            guard !cameras.isEmpty else { throw CameraHelperError.noCamerasAvailable }

            for camera in cameras {
                if camera.position == .front {
                    self.frontCamera = camera
                }

                if camera.position == .back {
                    self.rearCamera = camera

                    try camera.lockForConfiguration()
                    camera.focusMode = .continuousAutoFocus
                    camera.unlockForConfiguration()
                }
            }
        }

        func configureDeviceInputs() throws {
            guard let captureSession = self.captureSession else { throw CameraHelperError.captureSessionIsMissing }

            if let rearCamera = self.rearCamera {
                self.rearCameraInput = try AVCaptureDeviceInput(device: rearCamera)

                if captureSession.canAddInput(self.rearCameraInput!) { captureSession.addInput(self.rearCameraInput!) }

                self.currentCameraPosition = .rear
            }

            else if let frontCamera = self.frontCamera {
                self.frontCameraInput = try AVCaptureDeviceInput(device: frontCamera)

                if captureSession.canAddInput(self.frontCameraInput!) { captureSession.addInput(self.frontCameraInput!) }
                else { throw CameraHelperError.inputsAreInvalid }

                self.currentCameraPosition = .front
            }

            else { throw CameraHelperError.noCamerasAvailable }
        }

        func configurePhotoOutput() throws {
            guard let captureSession = self.captureSession else { throw CameraHelperError.captureSessionIsMissing }

            self.photoOutput = AVCapturePhotoOutput()
            self.photoOutput!.setPreparedPhotoSettingsArray([AVCapturePhotoSettings(format: [AVVideoCodecKey : AVVideoCodecType.jpeg])], completionHandler: nil)

            if captureSession.canAddOutput(self.photoOutput!) { captureSession.addOutput(self.photoOutput!) }
            captureSession.startRunning()
        }

        DispatchQueue(label: "prepare").async {
            do {
                createCaptureSession()
                try configureCaptureDevices()
                try configureDeviceInputs()
                try configurePhotoOutput()
            }

            catch {
                DispatchQueue.main.async {
                    completionHandler(error)
                }

                return
            }

            DispatchQueue.main.async {
                completionHandler(nil)
            }
        }
    }

    func displayPreview(on view: UIView) throws {
        guard let captureSession = self.captureSession, captureSession.isRunning else { throw CameraHelperError.captureSessionIsMissing }

        self.previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        self.previewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
        self.previewLayer?.connection?.videoOrientation = .portrait

        view.layer.insertSublayer(self.previewLayer!, at: 0)
        self.previewLayer?.frame = view.frame
    }

    func switchCameras() throws {
        guard let currentCameraPosition = currentCameraPosition, let captureSession = self.captureSession, captureSession.isRunning else { throw CameraHelperError.captureSessionIsMissing }

        captureSession.beginConfiguration()

        func switchToFrontCamera() throws {

            guard let rearCameraInput = self.rearCameraInput, captureSession.inputs.contains(rearCameraInput),
                let frontCamera = self.frontCamera else { throw CameraHelperError.invalidOperation }

            self.frontCameraInput = try AVCaptureDeviceInput(device: frontCamera)

            captureSession.removeInput(rearCameraInput)

            if captureSession.canAddInput(self.frontCameraInput!) {
                captureSession.addInput(self.frontCameraInput!)

                self.currentCameraPosition = .front
            }

            else {
                throw CameraHelperError.invalidOperation
            }
        }

        func switchToRearCamera() throws {

            guard let frontCameraInput = self.frontCameraInput, captureSession.inputs.contains(frontCameraInput),
                let rearCamera = self.rearCamera else { throw CameraHelperError.invalidOperation }

            self.rearCameraInput = try AVCaptureDeviceInput(device: rearCamera)

            captureSession.removeInput(frontCameraInput)

            if captureSession.canAddInput(self.rearCameraInput!) {
                captureSession.addInput(self.rearCameraInput!)

                self.currentCameraPosition = .rear
            }

            else { throw CameraHelperError.invalidOperation }
        }

        switch currentCameraPosition {
        case .front:
            try switchToRearCamera()

        case .rear:
            try switchToFrontCamera()
        }

        captureSession.commitConfiguration()
    }

    func captureImage(completion: @escaping (UIImage?, Error?) -> Void) {
        guard let captureSession = captureSession, captureSession.isRunning else { completion(nil, CameraHelperError.captureSessionIsMissing); return }

        let settings = AVCapturePhotoSettings()
        settings.flashMode = self.flashMode

        self.photoOutput?.capturePhoto(with: settings, delegate: self)
        self.photoCaptureCompletionBlock = completion
    }

}

extension CameraHelper: AVCapturePhotoCaptureDelegate {
    public func photoOutput(_ captureOutput: AVCapturePhotoOutput, didFinishProcessingPhoto photoSampleBuffer: CMSampleBuffer?, previewPhoto previewPhotoSampleBuffer: CMSampleBuffer?,
                            resolvedSettings: AVCaptureResolvedPhotoSettings, bracketSettings: AVCaptureBracketedStillImageSettings?, error: Swift.Error?) {
        if let error = error { self.photoCaptureCompletionBlock?(nil, error) }

        else if let buffer = photoSampleBuffer, let data = AVCapturePhotoOutput.jpegPhotoDataRepresentation(forJPEGSampleBuffer: buffer, previewPhotoSampleBuffer: nil),
            let image = UIImage(data: data) {

            self.photoCaptureCompletionBlock?(image, nil)
        }

        else {
            self.photoCaptureCompletionBlock?(nil, CameraHelperError.unknown)
        }
    }
}


extension CameraHelper {
    enum CameraHelperError: Swift.Error {
        case captureSessionAlreadyRunning
        case captureSessionIsMissing
        case inputsAreInvalid
        case invalidOperation
        case noCamerasAvailable
        case unknown
    }

    public enum CameraPosition {
        case front
        case rear
    }
}

这就是助手类。

Answer 1

使用.builtInWideAngleCamera而不是.builtInDualCamera来安装AVCaptureDevice。

在项目中替换此函数

func configureCaptureDevices() throws {

    let session = AVCaptureDevice.DiscoverySession(deviceTypes: [. builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)

    let cameras = session.devices.compactMap { $0 }
    guard !cameras.isEmpty else { throw CameraHelperError.noCamerasAvailable }

    for camera in cameras {
        if camera.position == .front {
            self.frontCamera = camera
        }

        if camera.position == .back {
            self.rearCamera = camera

            try camera.lockForConfiguration()
            camera.focusMode = .continuousAutoFocus
            camera.unlockForConfiguration()
        }
    }
}