Swiftでの動画撮影を一定時間ごとに自動保存

###前提・実現したいこと

Swiftで動画撮影を続けながら、一定時間ごとに自動保存したいです。
音声は必要ありません。

AVCaptureOutputとAVAssetWriterを使って試行錯誤しているのですが、
書き出すと撮影が止まってしまったり、上手くいきません。

ご教授いただけたら幸いです。

###該当のソースコード

import UIKit
import AVFoundation

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {
    
    fileprivate var writer: AVAssetWriter!
    fileprivate var videoInput: AVAssetWriterInput!
    fileprivate var audioInput: AVAssetWriterInput!
    
    var counter:Int = 0
    
	override func viewDidLoad() {
		super.viewDidLoad()
		setupCameraSession()
        
        // データ保存のパス
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let documentsDirectory = paths[0] as String
        let filePath : String? = "(documentsDirectory)/temp.mov"
        if FileManager.default.fileExists(atPath: filePath!) {
            try? FileManager.default.removeItem(atPath: filePath!)
        }
        
        writer = try? AVAssetWriter(outputURL: URL(fileURLWithPath: filePath!), fileType: AVFileTypeQuickTimeMovie)
        
        // Video入力
        let videoOutputSettings: Dictionary<String, AnyObject> = [
            AVVideoCodecKey : AVVideoCodecH264 as AnyObject,
            AVVideoWidthKey : 789 as AnyObject,
            AVVideoHeightKey : 1280 as AnyObject
        ];
        videoInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoOutputSettings)
        videoInput.expectsMediaDataInRealTime = true
        writer.add(videoInput)
	}

	override func viewDidAppear(_ animated: Bool) {
		super.viewDidAppear(animated)

		view.layer.addSublayer(previewLayer)

        writer?.startWriting()
        writer?.startSession(atSourceTime: kCMTimeZero)
        
        cameraSession.startRunning()
	}

	lazy var cameraSession: AVCaptureSession = {
		let s = AVCaptureSession()
		s.sessionPreset = AVCaptureSessionPresetLow
		return s
	}()

	lazy var previewLayer: AVCaptureVideoPreviewLayer = {
		let preview =  AVCaptureVideoPreviewLayer(session: self.cameraSession)
		preview?.bounds = CGRect(x: 0, y: 0, width: self.view.bounds.width, height: self.view.bounds.height)
		preview?.position = CGPoint(x: self.view.bounds.midX, y: self.view.bounds.midY)
		preview?.videoGravity = AVLayerVideoGravityResize
		return preview!
	}()

	func setupCameraSession() {
		let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo) as AVCaptureDevice

		do {
			let deviceInput = try AVCaptureDeviceInput(device: captureDevice)
			
			cameraSession.beginConfiguration()

			if (cameraSession.canAddInput(deviceInput) == true) {
				cameraSession.addInput(deviceInput)
			}

			let dataOutput = AVCaptureVideoDataOutput()
			dataOutput.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString) : NSNumber(value: kCVPixelFormatType_420YpCbCr8BiPlanarFullRange as UInt32)]
			dataOutput.alwaysDiscardsLateVideoFrames = true

			if (cameraSession.canAddOutput(dataOutput) == true) {
				cameraSession.addOutput(dataOutput)
			}

			cameraSession.commitConfiguration()

			let queue = DispatchQueue(label: "com.test.keiteratail")
			dataOutput.setSampleBufferDelegate(self, queue: queue)

		}
		catch let error as NSError {
			NSLog("(error), (error.localizedDescription)")
		}
	}

	func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
		// Here you collect each frame and process it

        print("write")
        
        videoInput?.append(sampleBuffer!)
        
        counter = counter + 1
        fileCounter = fileCounter + 1
        
        if(counter > 10){
            writer.finishWriting(completionHandler: {
                print(self.writer.outputURL)

                // データ保存のパスを生成
                let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
                let documentsDirectory = paths[0] as String
                let filePath : String? = "(documentsDirectory)/temp_(self.counter).mov"
                if FileManager.default.fileExists(atPath: filePath!) {
                    try? FileManager.default.removeItem(atPath: filePath!)
                }
            
                writer = try? AVAssetWriter(outputURL: URL(fileURLWithPath: filePath!), fileType: AVFileTypeQuickTimeMovie)

                writer?.startWriting()
                writer?.startSession(atSourceTime: kCMTimeZero)
            })
            counter = 0
                        
        }
	}

}