CvPhotoCamera and memory warning

Question

I have a question about CvPhotoCamera (OpenCV) in the iOS App.

I have a myViewController1: in this viewController I push a mySecondView controller.

In this second View Controller I use CvPhotoCamera:

I have a UIImageViewController.

In viewDidLoad I have this code:

- (void)viewDidLoad
{
    [super viewDidLoad];

    _photoCamera = [[CvPhotoCamera alloc] initWithParentView:imageView];
    _photoCamera.defaultAVCaptureSessionPreset = AVCaptureSessionPresetPhoto;
    _photoCamera.defaultAVCaptureVideoOrientation = AVCaptureVideoOrientationPortrait;
    [_photoCamera setDefaultAVCaptureDevicePosition:AVCaptureDevicePositionBack];
    _photoCamera.delegate = self;
    [_photoCamera start];
}

in viewDidDisappear I have this code:

- (void) viewDidDisappear:(BOOL)animated
{
    [_photoCamera stop];
}

I use CvPhotoCamera to take a photo from camera using the method:

- (IBAction)actionStart:(id)sender;
{
    [_photoCamera takePicture];

}

The my problem is this:

When I push this second ViewController and I tap on back button on Nav bar I have some memoryWarning and the app crashes ..always!!!

I used also the profile Xcode tool to manage memory allocation or memory leak but I do not see anything strange.

Is correct this use of CvPhotoCamera obj?