didOutputSampleBuffer delegate not called
<p>didOutputSampleBuffer function in my code was not called. I don't know why it happened. Here's the code:</p>

<pre><code>import UIKit
import AVFoundation
import Accelerate

class ViewController: UIViewController {

var captureSession: AVCaptureSession?
var dataOutput: AVCaptureVideoDataOutput?
var customPreviewLayer: AVCaptureVideoPreviewLayer?

@IBOutlet weak var camView: UIView!

override func viewWillAppear(animated: Bool) {
    super.viewDidAppear(animated)
    captureSession?.startRunning()
    //setupCameraSession()
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    //captureSession?.startRunning()
    setupCameraSession()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func setupCameraSession() {
    // Session
    self.captureSession = AVCaptureSession()
    captureSession!.sessionPreset = AVCaptureSessionPreset1920x1080
    // Capture device
    let inputDevice: AVCaptureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    var deviceInput = AVCaptureDeviceInput()

    do {
        deviceInput = try AVCaptureDeviceInput(device: inputDevice)
    } catch let error as NSError {
        print(error)
    }
    if captureSession!.canAddInput(deviceInput) {
        captureSession!.addInput(deviceInput)
    }
    // Preview

    self.customPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    self.customPreviewLayer!.frame = camView.bounds
    self.customPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspect
    self.customPreviewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.Portrait
    camView.layer.addSublayer(self.customPreviewLayer!)
    print("Cam layer added")

    self.dataOutput = AVCaptureVideoDataOutput()
    self.dataOutput!.videoSettings = [
        String(kCVPixelBufferPixelFormatTypeKey) : Int(kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)
    ]

    dataOutput!.alwaysDiscardsLateVideoFrames = true
    if captureSession!.canAddOutput(dataOutput) {
        captureSession!.addOutput(dataOutput)
    }
    captureSession!.commitConfiguration()
    let queue: dispatch_queue_t = dispatch_queue_create("VideoQueue", DISPATCH_QUEUE_SERIAL)
    let delegate = VideoDelegate()
    dataOutput!.setSampleBufferDelegate(delegate, queue: queue)
}




 func captureOutput(captureOutput: AVCaptureOutput, didOutputSampleBuffer sampleBuffer: CMSampleBufferRef, fromConnection connection: AVCaptureConnection) {
    let imageBuffer: CVImageBufferRef = CMSampleBufferGetImageBuffer(sampleBuffer)!
    CVPixelBufferLockBaseAddress(imageBuffer, 0)
    // For the iOS the luma is contained in full plane (8-bit)
    let width: size_t = CVPixelBufferGetWidthOfPlane(imageBuffer, 0)
    let height: size_t = CVPixelBufferGetHeightOfPlane(imageBuffer, 0)
    let bytesPerRow: size_t = CVPixelBufferGetBytesPerRowOfPlane(imageBuffer, 0)
    let lumaBuffer: UnsafeMutablePointer = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0)
    let grayColorSpace: CGColorSpaceRef = CGColorSpaceCreateDeviceGray()!
    let context: CGContextRef = CGBitmapContextCreate(lumaBuffer, width, height, 8, bytesPerRow, grayColorSpace, CGImageAlphaInfo.NoneSkipFirst.rawValue)!
    let dstImageFilter: CGImageRef = CGBitmapContextCreateImage(context)!
    dispatch_sync(dispatch_get_main_queue(), {() -&gt; Void in
        self.customPreviewLayer!.contents = dstImageFilter as AnyObject
    })

}


}
</code></pre>

<p>And here is my VideoDelegate code:</p>

<pre><code>import Foundation
import AVFoundation
import UIKit

// Video Delegate
class VideoDelegate : NSObject, AVCaptureVideoDataOutputSampleBufferDelegate
{

    func captureOutput(captureOutput: AVCaptureOutput!,
        didOutputSampleBuffer sampleBuffer: CMSampleBuffer!,
        fromConnection connection: AVCaptureConnection!){
            print("hihi")

    }


    func captureOutput(captureOutput: AVCaptureOutput!,
        didDropSampleBuffer sampleBuffer: CMSampleBuffer!,
        fromConnection connection: AVCaptureConnection!){

            print("LOL")
    }


}
</code></pre>

<p>Why does"t my delegate get called and how to fix it? I've checked similar question on stack overflow but but i can't find a method to solve this. Please help.</p>