Save AVCaptureVideoDataOutput to movie file using AVAssetWriter in Swift

I was able to find out how to use AVAssetWriter. In case anyone else needs help the code I used is as follows:

func setUpWriter() {    do {        outputFileLocation = videoFileLocation()        videoWriter = try AVAssetWriter(outputURL: outputFileLocation!, fileType: AVFileType.mov)        // add video input        videoWriterInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: [            AVVideoCodecKey : AVVideoCodecType.h264,            AVVideoWidthKey : 720,            AVVideoHeightKey : 1280,            AVVideoCompressionPropertiesKey : [                AVVideoAverageBitRateKey : 2300000,                ],            ])        videoWriterInput.expectsMediaDataInRealTime = true        if videoWriter.canAdd(videoWriterInput) {            videoWriter.add(videoWriterInput)            print("video input added")        } else {            print("no input added")        }        // add audio input        audioWriterInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil)        audioWriterInput.expectsMediaDataInRealTime = true        if videoWriter.canAdd(audioWriterInput!) {            videoWriter.add(audioWriterInput!)            print("audio input added")        }        videoWriter.startWriting()    } catch let error {        debugPrint(error.localizedDescription)    }}func canWrite() -> Bool {    return isRecording && videoWriter != nil && videoWriter?.status == .writing} //video file location methodfunc videoFileLocation() -> URL {    let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString    let videoOutputUrl = URL(fileURLWithPath: documentsPath.appendingPathComponent("videoFile")).appendingPathExtension("mov")    do {    if FileManager.default.fileExists(atPath: videoOutputUrl.path) {        try FileManager.default.removeItem(at: videoOutputUrl)        print("file removed")    }    } catch {        print(error)    }    return videoOutputUrl}// MARK: AVCaptureVideoDataOutputSampleBufferDelegatefunc captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {    let writable = canWrite()    if writable,        sessionAtSourceTime == nil {        // start writing        sessionAtSourceTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)        videoWriter.startSession(atSourceTime: sessionAtSourceTime!)        //print("Writing")    }    if output == videoDataOutput {        connection.videoOrientation = .portrait        if connection.isVideoMirroringSupported {            connection.isVideoMirrored = true        }    }    if writable,        output == videoDataOutput,        (videoWriterInput.isReadyForMoreMediaData) {        // write video buffer        videoWriterInput.append(sampleBuffer)        //print("video buffering")    } else if writable,        output == audioDataOutput,        (audioWriterInput.isReadyForMoreMediaData) {        // write audio buffer        audioWriterInput?.append(sampleBuffer)        //print("audio buffering")    }}// MARK: Start recordingfunc start() {    guard !isRecording else { return }    isRecording = true    sessionAtSourceTime = nil    setUpWriter()    print(isRecording)    print(videoWriter)    if videoWriter.status == .writing {        print("status writing")    } else if videoWriter.status == .failed {        print("status failed")    } else if videoWriter.status == .cancelled {        print("status cancelled")    } else if videoWriter.status == .unknown {        print("status unknown")    } else {        print("status completed")    }}// MARK: Stop recordingfunc stop() {    guard isRecording else { return }    isRecording = false    videoWriterInput.markAsFinished()    print("marked as finished")    videoWriter.finishWriting { [weak self] in        self?.sessionAtSourceTime = nil    }    //print("finished writing \(self.outputFileLocation)")    captureSession.stopRunning()    performSegue(withIdentifier: "videoPreview", sender: nil)}

I now have another problem where this solution doesn't work when I'm using AVCaptureMetadataOutput, AVCaptureVideoDataOutput and AVCaptureAudioDataOutput together. The app crashes when I add AVCaptureAudioDataOutput.