Optimise camera for QR codes - iphone

Question

I have a AVCaptureDevice specifically to scan QR codes (using AVMetadataObjectTypeQRCode). My goal is to make QR code scanning as fast as possible.
Several settings of the AVCaptureDevice camera (e.g. focus and exposure) can be programmatically adjusted in iOS.
What camera optimisations I can make to minimise the time it takes to capture a QR code on an iPhone?

Answer 1

Most of those settings optimal values vary based on the environment (eg dark/bright room, near/far QR Code etc.), so unless you know your user's environment (eg if the app was used exclusively in factory assembly lines), the default is probably best.
However (according to this source), If you know that the QR code will be near the camera you can speed up autofocus by setting autoFocusRangeRestriction to a near range value. You could also make sure that smoothAutoFocusEnabled is set to false.

Answer 2

I was used AVCaptureDevice.
This code working find i was used this in my bar code app.try this code.
-(void)BarcodeStart
{
_highlightView = [[UIView alloc] init];
_highlightView.autoresizingMask = UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleRightMargin|UIViewAutoresizingFlexibleBottomMargin;
_highlightView.layer.borderColor = [UIColor lightGrayColor].CGColor;
_highlightView.layer.borderWidth = 3;
[barcameraView addSubview:_highlightView];
_label = [[UILabel alloc] init];
_label.frame = CGRectMake(0, self.view.bounds.size.height - 40, self.view.bounds.size.width, 40);
_label.autoresizingMask = UIViewAutoresizingFlexibleTopMargin;
_label.backgroundColor = [UIColor colorWithWhite:0.15 alpha:0.65];
_label.textColor = [UIColor whiteColor];
_label.textAlignment = NSTextAlignmentCenter;
_label.text = #"(none)";
[self.view addSubview:_label];
//BackBtn UP side Show
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
//[button addTarget:self action:#selector(aMethod:)forControlEvents:UIControlEventTouchDown];
UIImageView *img = [[UIImageView alloc] init];
button.frame = CGRectMake(3,19,30,30);
img.image = [UIImage imageNamed:#"backBtnImg.png"];
[button setImage:img.image forState:UIControlStateNormal];
[_highlightView addSubview:button];
//
_session = [[AVCaptureSession alloc] init];
_device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
NSError *error = nil;
_input = [AVCaptureDeviceInput deviceInputWithDevice:_device error:&error];
if (_input) {
[_session addInput:_input];
} else {
NSLog(#"Error: %#", error);
}
_output = [[AVCaptureMetadataOutput alloc] init];
[_output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
[_session addOutput:_output];
_output.metadataObjectTypes = [_output availableMetadataObjectTypes];
_prevLayer = [AVCaptureVideoPreviewLayer layerWithSession:_session];
// _prevLayer.frame = CGRectMake(20, 70, 280, 280);
_prevLayer.frame = barcameraView.bounds;
_prevLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[barcameraView.layer addSublayer:_prevLayer];
[_session startRunning];
[barcameraView bringSubviewToFront:_highlightView];
[self.view bringSubviewToFront:_label];
}