合并具有不同方向的视频

Question

我想合并多个视频，我想在最终视频中保留其实际方向。这是我的代码

    func mergeSelectedVideos() {
            let composition = AVMutableComposition()
            let videoTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
            let audioTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)

            var time: Double = 0.0

            for video in self.arrayOfSelectedVideoURL {
                let sourceAsset = AVAsset(url: video as URL)
                let videoAssetTrack = sourceAsset.tracks(withMediaType: AVMediaTypeVideo)[0]
                let audioAssetTrack = sourceAsset.tracks(withMediaType: AVMediaTypeAudio)[0]
                let atTime = CMTime(seconds: time, preferredTimescale:1)            
                do{
                    try videoTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, sourceAsset.duration) , of: videoAssetTrack, at: atTime)
                    try audioTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, sourceAsset.duration) , of: audioAssetTrack, at: atTime)
                }catch{
                    print("-----Something wrong.")
                }
                time +=  sourceAsset.duration.seconds
            }

            let mergedVideoURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/mergedVideo.mp4")
            let exporter: AVAssetExportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality)!
            exporter.outputFileType = AVFileTypeMPEG4
            exporter.outputURL = mergedVideoURL as URL
            removeFileAtURLIfExists(url: mergedVideoURL)
            exporter.exportAsynchronously(completionHandler:
                {
                    switch exporter.status
                    {
                        case AVAssetExportSessionStatus.failed:
                            print("failed \(String(describing: exporter.error))")
                        case AVAssetExportSessionStatus.cancelled:
                            print("cancelled \(String(describing: exporter.error))")
                        case AVAssetExportSessionStatus.unknown:
                            print("unknown\(String(describing: exporter.error))")
                        case AVAssetExportSessionStatus.waiting:
                            print("waiting\(String(describing: exporter.error))")
                        case AVAssetExportSessionStatus.exporting:
                            print("exporting\(String(describing: exporter.error))")
                        default:
                            print("-----Merged video exportation complete.\(self.mergedVideoURL)")
                    }
                })
}

使用此代码我可以合并多个视频，但是纵向视频会在合并视频中旋转。是否有可能以某种方式合并它们，纵向视频将保持纵向，横向视频将在最终视频中保持景观？我搜索了很多，但没有找到任何。