用avcapturesession切换摄像头

在这里使用这个教程： http : //www.musicalgeometry.com/? p=1297我用AVCaptureSession创build了一个自定义覆盖和图像捕获。

我正试图让用户在前后相机之间切换。 这里是我在CaptureSessionManager中的代码来切换摄像头：

- (void)addVideoInputFrontCamera:(BOOL)front { NSArray *devices = [AVCaptureDevice devices]; AVCaptureDevice *frontCamera; AVCaptureDevice *backCamera; for (AVCaptureDevice *device in devices) { //NSLog(@"Device name: %@", [device localizedName]); if ([device hasMediaType:AVMediaTypeVideo]) { if ([device position] == AVCaptureDevicePositionBack) { //NSLog(@"Device position : back"); backCamera = device; } else { //NSLog(@"Device position : front"); frontCamera = device; } } } NSError *error = nil; if (front) { AVCaptureDeviceInput *frontFacingCameraDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:frontCamera error:&error]; if (!error) { if ([[self captureSession] canAddInput:frontFacingCameraDeviceInput]) { [[self captureSession] addInput:frontFacingCameraDeviceInput]; } else { NSLog(@"Couldn't add front facing video input"); } } } else { AVCaptureDeviceInput *backFacingCameraDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error:&error]; if (!error) { if ([[self captureSession] canAddInput:backFacingCameraDeviceInput]) { [[self captureSession] addInput:backFacingCameraDeviceInput]; } else { NSLog(@"Couldn't add back facing video input"); } } } } 

现在在我的自定义覆盖控制器中，我像viewDidLoad中那样初始化所有东西：

 [self setCaptureManager:[[CaptureSessionManager alloc] init]]; [[self captureManager] addVideoInputFrontCamera:NO]; // set to YES for Front Camera, No for Back camera [[self captureManager] addStillImageOutput]; [[self captureManager] addVideoPreviewLayer]; CGRect layerRect = [[[self view] layer] bounds]; [[[self captureManager] previewLayer] setBounds:layerRect]; [[[self captureManager] previewLayer] setPosition:CGPointMake(CGRectGetMidX(layerRect),CGRectGetMidY(layerRect))]; [[[self view] layer] addSublayer:[[self captureManager] previewLayer]]; [[_captureManager captureSession] startRunning]; 

开关相机button连接到一个名为switchCamera的方法。 我试过这个：

 - (void)switchCameraView:(id)sender { [[self captureManager] addVideoInputFrontCamera:YES]; // set to YES for Front Camera, No for Back camera } 

当调用这个时，我从CaptureSessionManager得到错误的NSLog，我不明白为什么。 在viewDidLoad中，如果我将fontCamera设置为YES，它将显示前置摄像头，但不能切换回来，反之亦然。

任何想法如何让它正确地切换？

Answer 1

您首先需要从AVCaptureSession中删除现有的AVCameraInput，然后将新的AVCameraInput添加到AVCaptureSession中。 以下适用于我（在ARC下）：

 -(IBAction)switchCameraTapped:(id)sender { //Change camera source if(_captureSession) { //Indicate that some changes will be made to the session [_captureSession beginConfiguration]; //Remove existing input AVCaptureInput* currentCameraInput = [_captureSession.inputs objectAtIndex:0]; [_captureSession removeInput:currentCameraInput]; //Get new input AVCaptureDevice *newCamera = nil; if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack) { newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront]; } else { newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack]; } //Add input to session NSError *err = nil; AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err]; if(!newVideoInput || err) { NSLog(@"Error creating capture device input: %@", err.localizedDescription); } else { [_captureSession addInput:newVideoInput]; } //Commit all the configuration changes at once [_captureSession commitConfiguration]; } } // Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found - (AVCaptureDevice *) cameraWithPosition:(AVCaptureDevicePosition) position { NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo]; for (AVCaptureDevice *device in devices) { if ([device position] == position) return device; } return nil; } 

Answer 2

Swift 3编辑（与François-Julien Alcaraz结合的答案）：

 @IBAction func switchCameraTapped(sender: Any) { //Change camera source if let session = captureSession { //Indicate that some changes will be made to the session session.beginConfiguration() //Remove existing input guard let currentCameraInput: AVCaptureInput = session.inputs.first as? AVCaptureInput else { return } session.removeInput(currentCameraInput) //Get new input var newCamera: AVCaptureDevice! = nil if let input = currentCameraInput as? AVCaptureDeviceInput { if (input.device.position == .back) { newCamera = cameraWithPosition(position: .front) } else { newCamera = cameraWithPosition(position: .back) } } //Add input to session var err: NSError? var newVideoInput: AVCaptureDeviceInput! do { newVideoInput = try AVCaptureDeviceInput(device: newCamera) } catch let err1 as NSError { err = err1 newVideoInput = nil } if newVideoInput == nil || err != nil { print("Error creating capture device input: \(err?.localizedDescription)") } else { session.addInput(newVideoInput) } //Commit all the configuration changes at once session.commitConfiguration() } } // Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found func cameraWithPosition(position: AVCaptureDevicePosition) -> AVCaptureDevice? { if let discoverySession = AVCaptureDeviceDiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaTypeVideo, position: .unspecified) { for device in discoverySession.devices { if device.position == position { return device } } } return nil } 

Swift版本到@ NES_4Life的回答：

 @IBAction func switchCameraTapped(sender: AnyObject) { //Change camera source if let session = captureSession { //Indicate that some changes will be made to the session session.beginConfiguration() //Remove existing input let currentCameraInput:AVCaptureInput = session.inputs.first as! AVCaptureInput session.removeInput(currentCameraInput) //Get new input var newCamera:AVCaptureDevice! = nil if let input = currentCameraInput as? AVCaptureDeviceInput { if (input.device.position == .Back) { newCamera = cameraWithPosition(.Front) } else { newCamera = cameraWithPosition(.Back) } } //Add input to session var err: NSError? var newVideoInput: AVCaptureDeviceInput! do { newVideoInput = try AVCaptureDeviceInput(device: newCamera) } catch let err1 as NSError { err = err1 newVideoInput = nil } if(newVideoInput == nil || err != nil) { print("Error creating capture device input: \(err!.localizedDescription)") } else { session.addInput(newVideoInput) } //Commit all the configuration changes at once session.commitConfiguration() } } // Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found func cameraWithPosition(position: AVCaptureDevicePosition) -> AVCaptureDevice? { let devices = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo) for device in devices { let device = device as! AVCaptureDevice if device.position == position { return device } } return nil } 

Answer 3

基于以前的答案，我做了一些validation和一个具体更改我自己的版本，当前的摄像头input可能不是捕捉会话的input的第一个对象，所以我改变了这一点：

 //Remove existing input AVCaptureInput* currentCameraInput = [self.captureSession.inputs objectAtIndex:0]; [self.captureSession removeInput:currentCameraInput]; 

为此（删除所有videotypes的input）：

 for (AVCaptureDeviceInput *input in self.captureSession.inputs) { if ([input.device hasMediaType:AVMediaTypeVideo]) { [self.captureSession removeInput:input]; break; } } 

以下是整个代码：

 if (!self.captureSession) return; [self.captureSession beginConfiguration]; AVCaptureDeviceInput *currentCameraInput; // Remove current (video) input for (AVCaptureDeviceInput *input in self.captureSession.inputs) { if ([input.device hasMediaType:AVMediaTypeVideo]) { [self.captureSession removeInput:input]; currentCameraInput = input; break; } } if (!currentCameraInput) return; // Switch device position AVCaptureDevicePosition captureDevicePosition = AVCaptureDevicePositionUnspecified; if (currentCameraInput.device.position == AVCaptureDevicePositionBack) { captureDevicePosition = AVCaptureDevicePositionFront; } else { captureDevicePosition = AVCaptureDevicePositionBack; } // Select new camera AVCaptureDevice *newCamera; NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo]; for (AVCaptureDevice *captureDevice in devices) { if (captureDevice.position == captureDevicePosition) { newCamera = captureDevice; } } if (!newCamera) return; // Add new camera input NSError *error; AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&error]; if (!error && [self.captureSession canAddInput:newVideoInput]) { [self.captureSession addInput:newVideoInput]; } [self.captureSession commitConfiguration]; 

Answer 4

Swift 3

 func switchCamera() { session?.beginConfiguration() let currentInput = session?.inputs.first as? AVCaptureDeviceInput session?.removeInput(currentInput) let newCameraDevice = currentInput?.device.position == .back ? getCamera(with: .front) : getCamera(with: .back) let newVideoInput = try? AVCaptureDeviceInput(device: newCameraDevice) session?.addInput(newVideoInput) session?.commitConfiguration() } // MARK: - Private extension CameraService { func getCamera(with position: AVCaptureDevicePosition) -> AVCaptureDevice? { guard let devices = AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo) as? [AVCaptureDevice] else { return nil } return devices.filter { $0.position == position }.first } } 

Answer 5

swift 3版本的cameraWithPosition没有弃用警告：

  // Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found func cameraWithPosition(_ position: AVCaptureDevicePosition) -> AVCaptureDevice? { if let deviceDescoverySession = AVCaptureDeviceDiscoverySession.init(deviceTypes: [AVCaptureDeviceType.builtInWideAngleCamera], mediaType: AVMediaTypeVideo, position: AVCaptureDevicePosition.unspecified) { for device in deviceDescoverySession.devices { if device.position == position { return device } } } return nil } 

如果您愿意，还可以通过更改deviceTypes数组来获取iPhone 7+（双摄像头）中的新设备types。

这是一个很好的阅读： https : //forums.developer.apple.com/thread/63347