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?

user_7082789 · Answer

Here is an updated version of chengsam's code that includes the fix for 'Multiple audio/video AVCaptureInputs are not currently supported'.

func switchCameraTapped() {
    //Change camera source
    //Indicate that some changes will be made to the session
    session.beginConfiguration()

    //Remove existing input
    guard let currentCameraInput: AVCaptureInput = session.inputs.first else {
        return
    }


    //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 let inputs = session.inputs as? [AVCaptureDeviceInput] {
        for input in inputs {
            session.removeInput(input)
        }
    }


    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
}

Switch cameras with avcapturesession

6 Answers