       guard CMTIME_IS_VALID(appendTime) else { print("No append time"); return }
 
       bufferQueue.async { [weak self] in
-
 
         self?.pixelBufferAdaptor.append(pixelBuffer, withPresentationTime: appendTime)
 


    let aVideoAssetTrack : AVAssetTrack = aVideoAsset.tracks(withMediaType: AVMediaTypeVideo)[0]
    let aAudioAssetTrack : AVAssetTrack = aAudioAsset.tracks(withMediaType: AVMediaTypeAudio)[0]



    do{
      try mutableCompositionVideoTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, aVideoAssetTrack.timeRange.duration), of: aVideoAssetTrack, at: kCMTimeZero)

  private var finishedCompletionHandler: ((_ url: URL) -> Void)? = nil

  @available(iOS 11.0, *)
  public convenience init(withARSCNView view: ARSCNView, options: Options = .`default`) throws {
    try self.init(scene: view, options: options)
  }

  public init(scene: SCNView, options: Options = .`default`) throws {

    self.sceneView = scene

