AVFoundation PDF417 scanner doesn't always work - swift

Question

I am creating an app using Swift 4 and Xcode 9 that scans PDF417 barcodes using AVFoundation. The scanner works with some codes but doesn't recognize the PDF417 barcode that you would find on the front of a CA Lottery scratchers ticket for example.
Is there anything I am missing to make it work? Below is my code:
let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInDualCamera], mediaType: AVMediaType.video, position: .back)
guard let captureDevice = deviceDiscoverySession.devices.first else {
print("Failed to get the camera device")
return
}
do {
captureSession = AVCaptureSession()
let input = try AVCaptureDeviceInput(device: captureDevice)
captureSession!.addInput(input)
let captureMetadataOutput = AVCaptureMetadataOutput()
captureSession!.addOutput(captureMetadataOutput)
captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
captureMetadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.pdf417]
videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
videoPreviewLayer?.frame = view.layer.bounds
view.layer.addSublayer(videoPreviewLayer!)
captureSession?.startRunning()
} catch {
print(error)
return
}
func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
//Get the metadata object
let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
if scanType.contains(metadataObj.type) {
let barCodeObj = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
if(metadataObj.stringValue != nil) {
callDelegate(metadataObj.stringValue)
captureSession?.stopRunning()
AudioServicesPlayAlertSound(SystemSoundID(kSystemSoundID_Vibrate))
navigationController?.popViewController(animated: true)
}
}
}
Thanks!

Answer 1

Replace your initialization code for the scanner with the following code either in your viewDidLoad or some method that you'd like it to be in
// Global vars used in init below
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
func setupCaptureInputDevice() {
let cameraMediaType = AVMediaType.video
captureSession = AVCaptureSession()
// get the video capture device, which should be of type video
guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else {
// if there is an error then something is wrong, so dismiss
dismiss(animated: true, completion: nil)
return
}
let videoInput: AVCaptureDeviceInput
// create a capture input for the above device input that was created
do {
videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
} catch {
return
}
// this is important to check for if we are able to add the input
// because adding before this could cause a crash or it could not happen
if (captureSession.canAddInput(videoInput)) {
captureSession.addInput(videoInput)
} else {
// dismiss or display error
return
}
// get ready to capture output somewhere
let metadataOutput = AVCaptureMetadataOutput()
// again check to make sure that we can do this operation before doing it
if (captureSession.canAddOutput(metadataOutput)) {
captureSession.addOutput(metadataOutput)
// setting the metadataOutput's delegate to be self and then requesting it run on the main thread
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
// specify your code type
metadataOutput.metadataObjectTypes = [.pdf417]
} else {
// dismiss or display error
return
}
// the preview layer now becomes the capture session
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
// just add it to the screen
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.addSublayer(previewLayer)
// and begin input
captureSession.startRunning()
}