AVAssetExportSession导出失败NSURErrorDomain代码-=3000（Swift）

这是我的密码：

            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)")
                }
            })

下面是错误消息：

2015-11-13 10:34:24.307 DemFishes[3501:63127]导出失败： 可选（错误域=nsurErrorDomain代码=-3000“无法创建文件” UserInfo={NSLocalizedDescription=无法创建文件， NSUnderlyingError=0x7ff5ee076460{错误域=NSOSStatusErrorDomain 代码=-12115“（空）”}）

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非常感谢您的帮助，谢谢

发现了我的错误。chunkURL不是有效的url

Hey@THall您能告诉我应该是什么chnkURL吗？我也有同样的问题。