Crash when using front camera ONLY on pre-iPhone 7 devices

Question

I've recently started running beta on my camera-based app. Everything is working as expected except on iPhone 6 devices.

The session starts on the back camera, and each time an iPhone 6 user switches to the front camera the app crashes. (And just to be really clear: no one on any other iPhone model is experiencing the issue.) I've gotten my hands on a 6 to test and can consistently reproduce the error, resulting in libc++abi.dylib: terminating with uncaught exception of type NSException .

I've tried starting the session on the front camera and it crashes immediately.

func initializeCamera() {
    self.captureSession.sessionPreset = .hd1920x1080

    let discovery = AVCaptureDevice.DiscoverySession.init(deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera],
                                                          mediaType: .video,
                                                          position: .unspecified) as AVCaptureDevice.DiscoverySession

    for device in discovery.devices as [AVCaptureDevice] {
        if device.hasMediaType(.video) {
            if device.position == AVCaptureDevice.Position.front {
                videoCaptureDevice = device
                do {
                    try currentDeviceInput = AVCaptureDeviceInput(device: device)
                } catch {
                    print("error: \(error.localizedDescription)")
                }
            }
        }
    }

    if videoCaptureDevice != nil {
        do {
            let videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice!)
            captureSession.addInput(videoInput)

            if let audioInput = AVCaptureDevice.default(for: .audio) {
                try captureSession.addInput(AVCaptureDeviceInput(device: audioInput))
            }

            previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)

            guard let previewLayer = previewLayer else { return }

            cameraPreviewView.frame = cameraContainer.frame

            cameraPreviewView.layer.addSublayer(previewLayer)
            previewLayer.frame = cameraPreviewView.frame

            previewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill

            setVideoOrientation()

            captureSession.addOutput(movieFileOutput)

            if let movieFileOutputConnection = movieFileOutput.connection(with: .video) {
                if movieFileOutputConnection.isVideoStabilizationSupported {
                    movieFileOutputConnection.preferredVideoStabilizationMode = .cinematic
                }
            }

            captureSession.startRunning()

            sessionIsReady(true)

        } catch {
            print("error: \(error.localizedDescription)")
        }
    }

}
func setVideoOrientation() {
    if let connection = self.previewLayer?.connection {
        if connection.isVideoOrientationSupported {
            connection.videoOrientation = .portrait
            previewLayer?.frame = cameraContainer.bounds
        }
    }
}

The crash is triggered at captureSession.addInput(videoInput) . videoInput is not nil . The camera's orientation is locked to portrait.

Can anyone offer any insight? Please let me know if any additional code would be helpful. Thanks in advance.

Answer 1

captureSession.addInput(videoInput) is causing the crash.

So you should use canAddInput(_:) before to avoid the crash.

if captureSession.canAddInput(videoInput) {
    captureSession.addInput(videoInput)
}

And in your case, captureSession.canAddInput(videoInput) == false with that iPhone 6.

Now, you are also doing self.captureSession.sessionPreset = .hd1920x1080

But according to WikiPedia , the iPhone 6 Front Camera hardware supports camera 1.2 MP (1280×960 px max.), 720p video recording (30 fps) . Doesn't seem to fit the 1920*1080 ("Full HD").

You could do this check what the "max" AVCaptureSession.Preset you can use.

func setSessionPreset(forDevice device: AVCaptureDevice) {
    let videoPresets: [AVCaptureSession.Preset] = [.hd4K3840x2160, .hd1920x1080, .hd1280x720] //etc. Put them in order to "preferred" to "last preferred"
    let preset = videoPresets.first(where: { device.supportsSessionPreset($0) }) ?? .hd1280x720
    captureSession.sessionPreset = preset
}