Switch cameras with avcapturesession

Question

Using this tutorial here: http://www.musicalgeometry.com/?p=1297 I have created a custom overlay and image capture with AVCaptureSession.

I am attempting to allow the user to switch between the front and back camera. Here is my code in CaptureSessionManager to switch cameras:

- (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");             }         }     } } 

Now in my custom overlay controller I initialize everything like so in viewDidLoad:

[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]; 

The switch camera button is connected to a method called switchCamera. I have tried this:

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

When calling this, I get the error NSLog from the CaptureSessionManager and I cannot figure out why. In viewDidLoad, if I set the fontCamera to YES, it shows the front camera but cannot switch to back, and vice versa.

Any ideas on how to get it to switch properly?

Answer 1

You first need to remove the existing AVCameraInput from the AVCaptureSession and then add a new AVCameraInput to the AVCaptureSession. The following works for me (under ARC):

-(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 4/5

@IBAction func switchCameraTapped(sender: Any) {     //Change camera source     if let session = captureSession {         //Remove existing input         guard let currentCameraInput: AVCaptureInput = session.inputs.first else {             return         }          //Indicate that some changes will be made to the session         session.beginConfiguration()         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: AVCaptureDevice.Position) -> AVCaptureDevice? {     let discoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)     for device in discoverySession.devices {         if device.position == position {             return device         }     }      return nil } 

Swift 3 Edit (Combined with François-Julien Alcaraz answer):

@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 version to @NES_4Life's answer:

@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 }