Reading QR Code

What I need to accomplish is matching the QR code to the one I have created. This code works, except it takes at least 30 seconds to verify that it has matched my QR Code. How can I make it faster?

QRCodeVC.h

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>

@interface QRCodeVC : UIViewController <AVCaptureMetadataOutputObjectsDelegate> {

NSTimer *timer;
}

@property (weak, nonatomic) IBOutlet UIView *viewPreview;
@property (strong, nonatomic) IBOutlet UIImageView *imageCheckmark;
@property (strong, nonatomic) IBOutlet UILabel *wrongQRCodeLabel;
@property(nonatomic, assign) NSString *messageString;

@end

QRCodeVC.m

#import "QRCodeVC.h"
#import <Parse/Parse.h>

@interface QRCodeVC ()

@property (nonatomic, strong) AVCaptureSession *captureSession;
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *videoPreviewLayer;
@property (nonatomic, strong) AVAudioPlayer *audioPlayer;
@property (nonatomic) BOOL isReading;

-(BOOL)startReading;
-(void)stopReading;
-(void)loadBeepSound;

@end

@implementation QRCodeVC

- (void)viewDidLoad {
[super viewDidLoad];

timer = [NSTimer scheduledTimerWithTimeInterval:(1.0/2.0) target:self selector:@selector(loading) userInfo:nil repeats:YES];

if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {
    self.navigationController.interactivePopGestureRecognizer.enabled = YES;
}

self.imageCheckmark.image = [UIImage imageNamed:@""];

// Initially make the captureSession object nil.
_captureSession = nil;

// Set the initial value of the flag to NO.
_isReading = NO;

// Begin loading the sound effect so to have it ready for playback when it's needed.
[self loadBeepSound];

self.viewPreview.layer.cornerRadius = 20;
self.viewPreview.layer.masksToBounds = YES;
}

- (void) viewWillAppear:(BOOL)animated {


[self.navigationController.navigationBar setHidden:NO];

// Navigation Bar Attibutes
self.navigationController.navigationBar.barTintColor = [UIColor redColor];
self.navigationController.navigationBar.tintColor = [UIColor whiteColor];
[self.navigationController.navigationBar
 setTitleTextAttributes:@{NSForegroundColorAttributeName : [UIColor whiteColor]}];
self.navigationController.navigationBar.translucent = NO;

if (!_isReading) {
    // This is the case where the app should read a QR code when the start button is tapped.
    if ([self startReading]) {

    }
}
else{
    // In this case the app is currently reading a QR code and it should stop doing so.
    [self stopReading];
}

// Set to the flag the exact opposite value of the one that currently has.
_isReading = !_isReading;
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

#pragma mark - Private method implementation

- (BOOL)startReading {
NSError *error;

// Get an instance of the AVCaptureDevice class to initialize a device object and provide the video
// as the media type parameter.
AVCaptureDevice *captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

// Get an instance of the AVCaptureDeviceInput class using the previous device object.
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:&error];

if (!input) {
    // If any error occurs, simply log the description of it and don't continue any more.
    NSLog(@"%@", [error localizedDescription]);
    return NO;
}

// Initialize the captureSession object.
_captureSession = [[AVCaptureSession alloc] init];
// Set the input device on the capture session.
[_captureSession addInput:input];


// Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
AVCaptureMetadataOutput *captureMetadataOutput = [[AVCaptureMetadataOutput alloc] init];
[_captureSession addOutput:captureMetadataOutput];

// Create a new serial dispatch queue.
dispatch_queue_t dispatchQueue;
dispatchQueue = dispatch_queue_create("myQueue", NULL);
[captureMetadataOutput setMetadataObjectsDelegate:self queue:dispatchQueue];
[captureMetadataOutput setMetadataObjectTypes:[NSArray arrayWithObject:AVMetadataObjectTypeQRCode]];

// Initialize the video preview layer and add it as a sublayer to the viewPreview view's layer.
_videoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:_captureSession];
[_videoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
[_videoPreviewLayer setFrame:_viewPreview.layer.bounds];
[_viewPreview.layer addSublayer:_videoPreviewLayer];


self.messageString = AVMetadataObjectTypeQRCode;

// Start video capture.
[_captureSession startRunning];

return YES;
}


-(void)stopReading{

//    self.imageCheckmark.image = [UIImage imageNamed:@"checkmark_RA"];

// Stop video capture and make the capture session object nil.
[_captureSession stopRunning];
_captureSession = nil;

/*
 // Remove the video preview layer from the viewPreview view's layer.
 [_videoPreviewLayer removeFromSuperlayer];
 */
}


-(void)loadBeepSound{
// Get the path to the beep.mp3 file and convert it to a NSURL object.
NSString *beepFilePath = [[NSBundle mainBundle] pathForResource:@"beep" ofType:@"mp3"];
NSURL *beepURL = [NSURL URLWithString:beepFilePath];

NSError *error;

// Initialize the audio player object using the NSURL object previously set.
_audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:beepURL error:&error];
if (error) {
    // If the audio player cannot be initialized then log a message.
    NSLog(@"Could not play beep file.");
    NSLog(@"%@", [error localizedDescription]);
}
else{
    // If the audio player was successfully initialized then load it in memory.
    [_audioPlayer prepareToPlay];
}
}


#pragma mark - AVCaptureMetadataOutputObjectsDelegate method implementation

-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection {








// It is very slow from here





// Check if the metadataObjects array is not nil and it contains at least one object.
if (metadataObjects != nil && [metadataObjects count] > 0) {
    // Get the metadata object.
    AVMetadataMachineReadableCodeObject *metadataObj = [metadataObjects objectAtIndex:0];
    if ([[metadataObj type] isEqualToString:AVMetadataObjectTypeQRCode]) {

        NSString *scanResult = [metadataObj stringValue];

        if ([scanResult isEqualToString:@"myQRCode"]) {

            self.imageCheckmark.image = [UIImage imageNamed:@"checkmark_RA"];


            [[PFUser currentUser] incrementKey:@"Points" byAmount:[NSNumber numberWithInt:1]];
            [[PFUser currentUser] saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
                if (succeeded) {
                    NSLog(@"The object has been saved.");
                } else {
                    NSLog(@"There was a problem");
                }
            }];


             {
            // }

            UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Congratulations!" message:@"1 point has been added to your account" delegate:nil cancelButtonTitle:@"Yes!" otherButtonTitles:nil];

            [alertView show];

            NSLog(@"Correct QR Code!");

        } else {

            self.wrongQRCodeLabel.text = @"Wrong QR Code!";
            NSLog(@"Wrong QR Code!");

        }

        NSLog(@"%@", scanResult);






// To here







        // If the found metadata is equal to the QR code metadata then update the status label's text,
        // stop reading and change the bar button item's title and the flag's value.
        // Everything is done on the main thread

        [self performSelectorOnMainThread:@selector(stopReading) withObject:nil waitUntilDone:NO];

        _isReading = NO;

        // If the audio player is not nil, then play the sound effect.
        if (_audioPlayer) {
            [_audioPlayer play];
        }
    }
}
}

- (void) loading {
    }

@end