CIContext initialization crash - ios

Question

Background:
I'm running a swift 2 application with the following two options.
Option A:
The user can enter a number to sign in. In this case, his/her picture is shown in a UIImageView.
Option B:
The user can use an NFC tag to sign in. In this case, the UIImageView is replaced with a camera layer that shows live camera stream and uses CIContext to capture an image on a button press.
Problem:
The issue I'm facing is that sometimes, when I choose option A (not using the camera layer), the app crashes. Since I'm unable to reproduce the crash deterministically, I have hit a dead end to understand why the app is crashing.
EDIT: The camera layer is used in both options but is hidden in option A.
Crashlytics generates the following crash log:
0 libswiftCore.dylib specialized _fatalErrorMessage(StaticString, StaticString, StaticString, UInt) -> () + 44
1 CameraLayerView.swift line 20 CameraLayerView.init(coder : NSCoder) -> CameraLayerView?
2 CameraLayerView.swift line 0 #objc CameraLayerView.init(coder : NSCoder) -> CameraLayerView?
3 UIKit -[UIClassSwapper initWithCoder:] + 248
32 UIKit UIApplicationMain + 208
33 AppDelegate.swift line 17 main
34 libdispatch.dylib (Missing)
I've checked line#20 in CameraLayerView but it is just an initialization statement
private let ciContext = CIContext(EAGLContext: EAGLContext(API: .OpenGLES2))
Mentioned below is the CameraLayerView file. Any help would be appreciated
var captureSession = AVCaptureSession()
var sessionOutput = AVCaptureVideoDataOutput()
var previewLayer = AVCaptureVideoPreviewLayer()
private var pixelBuffer : CVImageBuffer!
private var attachments : CFDictionary!
private var ciImage : CIImage!
private let ciContext = CIContext(EAGLContext: EAGLContext(API: .OpenGLES2))
private var imageOptions : [String : AnyObject]!
var faceFound = false
var image : UIImage!
override func layoutSubviews() {
previewLayer.position = CGPoint(x: self.frame.width/2, y: self.frame.height/2)
previewLayer.bounds = self.frame
self.layer.borderWidth = 2.0
self.layer.borderColor = UIColor.redColor().CGColor
}
func loadCamera() {
let camera = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo)
for device in camera {
if device.position == .Front {
do{
for input in captureSession.inputs {
captureSession.removeInput(input as! AVCaptureInput)
}
for output in captureSession.outputs {
captureSession.removeOutput(output as! AVCaptureOutput)
}
previewLayer.removeFromSuperlayer()
previewLayer.session = nil
let input = try AVCaptureDeviceInput(device: device as! AVCaptureDevice)
if captureSession.canAddInput(input) {
captureSession.addInput(input)
sessionOutput.videoSettings = [String(kCVPixelBufferPixelFormatTypeKey) : Int(kCVPixelFormatType_32BGRA)]
sessionOutput.setSampleBufferDelegate(self, queue: dispatch_get_global_queue(Int(QOS_CLASS_BACKGROUND.rawValue), 0))
sessionOutput.alwaysDiscardsLateVideoFrames = true
if captureSession.canAddOutput(sessionOutput) {
captureSession.addOutput(sessionOutput)
captureSession.sessionPreset = AVCaptureSessionPresetPhoto
captureSession.startRunning()
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
switch UIDevice.currentDevice().orientation.rawValue {
case 1:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.Portrait
break
case 2:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.PortraitUpsideDown
break
case 3:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.LandscapeRight
break
case 4:
previewLayer.connection.videoOrientation = AVCaptureVideoOrientation.LandscapeLeft
break
default:
break
}
self.layer.addSublayer(previewLayer)
}
}
} catch {
print("Error")
}
}
}
}
func takePicture() -> UIImage {
self.previewLayer.removeFromSuperlayer()
self.captureSession.stopRunning()
return image
}
func captureOutput(captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {
pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate)
ciImage = CIImage(CVPixelBuffer: pixelBuffer!, options: attachments as? [String : AnyObject])
if UIDevice.currentDevice().orientation == .PortraitUpsideDown {
imageOptions = [CIDetectorImageOrientation : 8]
} else if UIDevice.currentDevice().orientation == .LandscapeLeft {
imageOptions = [CIDetectorImageOrientation : 3]
} else if UIDevice.currentDevice().orientation == .LandscapeRight {
imageOptions = [CIDetectorImageOrientation : 1]
} else {
imageOptions = [CIDetectorImageOrientation : 6]
}
let faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: ciContext, options: [CIDetectorAccuracy: CIDetectorAccuracyHigh])
let features = faceDetector.featuresInImage(ciImage, options: imageOptions)
if features.count == 0 {
if faceFound == true {
faceFound = false
dispatch_async(dispatch_get_main_queue()) {
self.layer.borderColor = UIColor.redColor().CGColor
}
}
} else {
if UIDevice.currentDevice().orientation == .PortraitUpsideDown {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Left)
} else if UIDevice.currentDevice().orientation == .LandscapeLeft {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Down)
} else if UIDevice.currentDevice().orientation == .LandscapeRight {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Up)
} else {
image = UIImage(CGImage: ciContext.createCGImage(ciImage, fromRect: ciImage.extent), scale: 1.0, orientation: UIImageOrientation.Right)
}
if faceFound == false {
faceFound = true
for feature in features {
if feature.isKindOfClass(CIFaceFeature) {
dispatch_async(dispatch_get_main_queue()) {
self.layer.borderColor = UIColor.greenColor().CGColor
}
}
}
}
}
}

Answer 1

I tested a theory and it worked. Since ciContext was being initialised with view initialisation, it seemed like the app was crashing due to a race condition. I moved the initialisation for ciContext into my loadCamera method and it hasn't crashed since.
UPDATE
Another thing I noticed was that, in various tutorials and blog posts on the internet, the statement let ciContext = CIContext(EAGLContext: EAGLContext(API: .OpenGLES2)) was declared in two seperate statements such that it became
let eaglContext = EAGLContext(API: .OpenGLES2)
let ciContext = CIContext(EAGLContext: eaglContext)
I still don't what exactly was causing the app to crash in the first place but these two changes seemed to have fix the problem
CORRECT ANSWER
Finally found the culprit. In my viewController that used ciContext, I had a timer that was not being invalidated hence keeping a strong reference to the viewController. On every subsequent visit, it would create a new viewController while the previous one was never released from memory. This resulted in the memory filling up overtime. Once it passed a certain threshold, the ciContext intialiser would return nil because of low memory which would in turn crash the app.