This error is mostly because you are trying to export an AVAsset. Solve this using AVMutableComposition for export. sample code for trimming a video file let manager = FileManager.default         guard let documentDirectory = try?  manager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)  else { print("TRIM Failed to access directory")             return}         let mediaType = "mp4"         if mediaType == kUTTypeMovie as String || mediaType == "mp4" as String {                let asset = AVAsset(url:videoURL!)             let length = Float(asset.duration.value) / Float(asset.duration.timescale)                print("TRIM video length: \(length) seconds")             let composition = AVMutableComposition()             let audioTrack: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)!             let videoTrack: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: kCMPersistentTrackID_Invalid)!             var outURL_speed=documentDirectory.appendingPathComponent("output")             var outputURL = documentDirectory.appendingPathComponent("output")                     do {                         try audioTrack.insertTimeRange(CMTimeRangeFromTimeToTime(start: self.startTime, end: self.endTime), of: asset.tracks(withMediaType: AVMediaType.audio)[0], at: CMTime.zero)                         try videoTrack.insertTimeRange(CMTimeRangeFromTimeToTime(start: self.startTime, end: self.endTime), of: asset.tracks(withMediaType: AVMediaType.video)[0], at: CMTime.zero)                                               try manager.createDirectory(at: outputURL, withIntermediateDirectories: true, attributes: nil)                         outputURL = outputURL.appendingPathComponent("preVideo-\(self.postID).\(mediaType)")                         outURL_speed = outURL_speed.appendingPathComponent("Video-\(self.postID).\(mediaType)")                         print("TRIM output dir: \(outputURL)")                     }catch let error {                         print(error)                     }             _ = try? manager.removeItem(at: outputURL)                                                             guard let exportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality) else {return}                          exportSession.outputURL = outputURL             exportSession.shouldOptimizeForNetworkUse = true             exportSession.outputFileType = .mp4             let timeRange = CMTimeRange(start: self.startTime, end: self.endTime)             exportSession.timeRange = timeRange                          exportSession.exportAsynchronously{                 switch exportSession.status {                 case .completed:                     print("TRIM exported at \(outputURL)")                     self.changeSpeed(url: outputURL,outUrl:outURL_speed)                 case .failed:                     print("TRIM failed \(exportSession.error)")                 case .cancelled:                     print("TRIM cancelled \(exportSession.error)")                 default: break                 }             }