Ошибка экспорта AVAssetExportSession NSURLErrorDomain Code- = 3000 (Swift)

Вот мой код:

            startTime = endTime
            endTime = CMTimeMake(startTime.value + chunkSize, duration!.timescale)
            if endTime > duration {
                endTime = duration!
            }

            let composition = AVMutableComposition()
            let videoCompTrack = composition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())

            let assetVideoTrack: AVAssetTrack = asset!.tracksWithMediaType(AVMediaTypeVideo).first!

            let chunkDuration = CMTimeSubtract(endTime, startTime)
            let chunkTimeRange = CMTimeRangeMake(startTime, chunkDuration)

            do {
                try videoCompTrack.insertTimeRange(chunkTimeRange, ofTrack: assetVideoTrack, atTime: kCMTimeZero)

            } catch let error as NSError {
                print("Video reversing chunking failure: \(error)")
            }

            let exportSession = AVAssetExportSession(asset: composition, presetName: preferredPreset)
            exportSession!.outputURL = chunkURL
            exportSession!.outputFileType = AVFileTypeQuickTimeMovie
            exportSession?.shouldOptimizeForNetworkUse = true

            removeFileAtURLIfExists(chunkURL)

            exportSession!.exportAsynchronouslyWithCompletionHandler({ () -> Void in
                switch (exportSession!.status) {
                case AVAssetExportSessionStatus.Completed:
                    NSLog("Export completed")
                case AVAssetExportSessionStatus.Cancelled:
                    NSLog("Export cancelled")
                    break;
                default:
                    NSLog("Export failed: \(exportSession?.error)")
                }
            })

И вот сообщение об ошибке:

2015-11-13 10: 34: 24.307 DemFishes [3501: 63127] Ошибка экспорта: необязательно (домен ошибки = NSURLErrorDomain Code = -3000 «Невозможно создать файл» UserInfo = {NSLocalizedDescription = Невозможно создать файл, NSUnderlyingError = 0x7ff5ee076460 {Error Domain = NSOSStatusErrorDomain Code = -12115 "(null)"}})

Любая помощь очень ценится, спасибо!