.swift

private func startLiveVideo() {
        
        session.sessionPreset = AVCaptureSession.Preset.photo
        let captureDevice = AVCaptureDevice.default(for: AVMediaType.video)
        
        let deviceInput = try! AVCaptureDeviceInput(device: captureDevice!)
        let deviceOutput = AVCaptureVideoDataOutput()
        deviceOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_32BGRA)]
        deviceOutput.setSampleBufferDelegate(self, queue: DispatchQueue.global(qos: DispatchQoS.QoSClass.default))
        session.addInput(deviceInput)
        session.addOutput(deviceOutput)

        let imageLayer = AVCaptureVideoPreviewLayer(session: session)
        imageLayer.frame = CGRect(x: 0, y: 0, width: self.imageView.frame.size.width + 100, height: self.imageView.frame.size.height)
        imageLayer.videoGravity = .resizeAspectFill
        imageView.layer.addSublayer(imageLayer)
        
        session.startRunning()
    }