iphone - How to stop SquareCamController Apple sample Demo project in Arc?

Question

In my App i am using the sample code provided by apple for face detection. The code was written prior to ARC and it has a lot of non arc code. I converted the project for Arc and its running fine in my ARC project. The only problem seems to be is i can see my nslog statements from that class still running and the App crashes after few minutes. If i put break points it also stops in that class which means after the view is dismissed it's still running in the background which eventually make it crash.

Here's the code where its crashing :

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{   
    // got an image
    CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CFDictionaryRef attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate);
    CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer options:(__bridge NSDictionary *)attachments];
    if (attachments)
        CFRelease(attachments);
    NSDictionary *imageOptions = nil;
    UIDeviceOrientation curDeviceOrientation = [[UIDevice currentDevice] orientation];
    int exifOrientation;

    /* kCGImagePropertyOrientation values
        The intended display orientation of the image. If present, this key is a CFNumber value with the same value as defined
        by the TIFF and EXIF specifications -- see enumeration of integer constants. 
        The value specified where the origin (0,0) of the image is located. If not present, a value of 1 is assumed.

        used when calling featuresInImage: options: The value for this key is an integer NSNumber from 1..8 as found in kCGImagePropertyOrientation.
        If present, the detection will be done based on that orientation but the coordinates in the returned features will still be based on those of the image. */

    enum {
        PHOTOS_EXIF_0ROW_TOP_0COL_LEFT          = 1, //   1  =  0th row is at the top, and 0th column is on the left (THE DEFAULT).
        PHOTOS_EXIF_0ROW_TOP_0COL_RIGHT         = 2, //   2  =  0th row is at the top, and 0th column is on the right.  
        PHOTOS_EXIF_0ROW_BOTTOM_0COL_RIGHT      = 3, //   3  =  0th row is at the bottom, and 0th column is on the right.  
        PHOTOS_EXIF_0ROW_BOTTOM_0COL_LEFT       = 4, //   4  =  0th row is at the bottom, and 0th column is on the left.  
        PHOTOS_EXIF_0ROW_LEFT_0COL_TOP          = 5, //   5  =  0th row is on the left, and 0th column is the top.  
        PHOTOS_EXIF_0ROW_RIGHT_0COL_TOP         = 6, //   6  =  0th row is on the right, and 0th column is the top.  
        PHOTOS_EXIF_0ROW_RIGHT_0COL_BOTTOM      = 7, //   7  =  0th row is on the right, and 0th column is the bottom.  
        PHOTOS_EXIF_0ROW_LEFT_0COL_BOTTOM       = 8  //   8  =  0th row is on the left, and 0th column is the bottom.  
    };

    switch (curDeviceOrientation) {
        case UIDeviceOrientationPortraitUpsideDown:  // Device oriented vertically, home button on the top
            exifOrientation = PHOTOS_EXIF_0ROW_LEFT_0COL_BOTTOM;
            break;
        case UIDeviceOrientationLandscapeLeft:       // Device oriented horizontally, home button on the right
            if (isUsingFrontFacingCamera)
                exifOrientation = PHOTOS_EXIF_0ROW_BOTTOM_0COL_RIGHT;
            else
                exifOrientation = PHOTOS_EXIF_0ROW_TOP_0COL_LEFT;
            break;
        case UIDeviceOrientationLandscapeRight:      // Device oriented horizontally, home button on the left
            if (isUsingFrontFacingCamera)
                exifOrientation = PHOTOS_EXIF_0ROW_TOP_0COL_LEFT;
            else
                exifOrientation = PHOTOS_EXIF_0ROW_BOTTOM_0COL_RIGHT;
            break;
        case UIDeviceOrientationPortrait:            // Device oriented vertically, home button on the bottom
        default:
            exifOrientation = PHOTOS_EXIF_0ROW_RIGHT_0COL_TOP;
            break;
    }

    imageOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:exifOrientation] forKey:CIDetectorImageOrientation];
    NSArray *features = [faceDetector featuresInImage:ciImage options:imageOptions];

    // get the clean aperture
    // the clean aperture is a rectangle that defines the portion of the encoded pixel dimensions
    // that represents image data valid for display.
    CMFormatDescriptionRef fdesc = CMSampleBufferGetFormatDescription(sampleBuffer);
    CGRect clap = CMVideoFormatDescriptionGetCleanAperture(fdesc, false /*originIsTopLeft == false*/);

    dispatch_async(dispatch_get_main_queue(), ^(void) {
        [self drawFaceBoxesForFeatures:features forVideoBox:clap orientation:curDeviceOrientation]; --------->>>>>> Its crashing here
    });
}