AVCaptureVideoDataOutput captureOutput not being called

Question

I\'m trying screen capture on a Mac with AVCaptureScreenInput, but AVCaptureVideoDataOutput delegate captureOutput is never called, and I\'m not sure why. I do get a notific

Answer 1

You need to define the didOutputSampleBuffer delegate callback to actually receive the captured frames:

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

p.s. I'm not sure about macOS, but viewWillAppear may not be a good place to do initialisation because on iOS at least it can be called multiple times.

Answer 2

---

I added for basic example AVCaptureVideoDataOutputSampleBufferDelegate

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {    


    let videoQueue = DispatchQueue(label: "VIDEO_QUEUE")

    override func viewDidLoad() {
        super.viewDidLoad()

        let captureSession = AVCaptureSession()

        guard let captureDevice = AVCaptureDevice.default(for: .video) else { return }

        guard let input = try? AVCaptureDeviceInput(device: captureDevice) else { return }

        captureSession.addInput(input)

        captureSession.startRunning()

        let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        view.layer.addSublayer(previewLayer)
        previewLayer.frame = view.frame

        let dataOutput = AVCaptureVideoDataOutput()
        dataOutput.setSampleBufferDelegate(self, queue: videoQueue)
        captureSession.addOutput(dataOutput)
    }

    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        print("Camera was able to capture a frame:", Date())
    }
}