avassetexport return the video in landscape - ios

Question

I've created this function which get a video which is captured in portraitmode. however when i save the avassetexport and show it, it seems like it identify it as landscape, how can i make sure to create this as a portrait video??
func createVideo() -> AVAssetExportSession {
let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString
let fileURL = NSURL(fileURLWithPath: "\(documentsPath)/pre.mov")
let composition = AVMutableComposition()
let vidAsset = AVURLAsset(URL: fileURL, options: nil)
// get video track
let vtrack = vidAsset.tracksWithMediaType(AVMediaTypeVideo)
let videoTrack:AVAssetTrack = vtrack[0]
let vid_timerange = CMTimeRangeMake(kCMTimeZero, vidAsset.duration)
do {
let compositionvideoTrack:AVMutableCompositionTrack = composition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
try compositionvideoTrack.insertTimeRange(vid_timerange, ofTrack: videoTrack, atTime: kCMTimeZero)
compositionvideoTrack.preferredTransform = videoTrack.preferredTransform
} catch {
print(error)
}
//Get the video
let fullSizeImage = videoTrack
print(fullSizeImage.naturalSize)
let newOverLayHeight = fullSizeImage.naturalSize.width / self.containerView!.frame.width * self.containerView!.frame.height
UIGraphicsBeginImageContext(CGSizeMake(fullSizeImage.naturalSize.width, newOverLayHeight));
self.containerView!.drawViewHierarchyInRect(CGRectMake(0, 0, fullSizeImage.naturalSize.width, newOverLayHeight), afterScreenUpdates: true)
let overlayImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
let imglogo = UIImage(named: "image.png")
let imglayer = CALayer()
imglayer.contents = imglogo?.CGImage
imglayer.frame = CGRectMake(0,fullSizeImage.naturalSize.height - newOverLayHeight, overlayImage.size.width, overlayImage.size.height)
let videolayer = CALayer()
videolayer.frame = CGRectMake(0, 0, fullSizeImage.naturalSize.width, fullSizeImage.naturalSize.height)
let parentlayer = CALayer()
parentlayer.frame = CGRectMake(0, 0, fullSizeImage.naturalSize.width, fullSizeImage.naturalSize.height)
parentlayer.addSublayer(videolayer)
parentlayer.addSublayer(imglayer)
let layercomposition = AVMutableVideoComposition()
layercomposition.frameDuration = CMTimeMake(1, 30)
layercomposition.renderSize = fullSizeImage.naturalSize
layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, inLayer: parentlayer)
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
let videotrack = composition.tracksWithMediaType(AVMediaTypeVideo)[0] as AVAssetTrack
let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
instruction.layerInstructions = NSArray(object: layerinstruction) as! [AVVideoCompositionLayerInstruction]
layercomposition.instructions = NSArray(object: instruction) as! [AVVideoCompositionInstructionProtocol]
// create new file to receive data
let docsDir: AnyObject = documentsPath
let movieFilePath = docsDir.stringByAppendingPathComponent("result.mov")
let movieDestinationUrl = NSURL(fileURLWithPath: movieFilePath)
_ = try? NSFileManager().removeItemAtURL(movieDestinationUrl)
let preFilePath = docsDir.stringByAppendingPathComponent("pre.mov")
let preDestinationUrl = NSURL(fileURLWithPath: preFilePath)
_ = try? NSFileManager().removeItemAtURL(preDestinationUrl)
// use AVAssetExportSession to export video
let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality)
assetExport!.outputFileType = AVFileTypeQuickTimeMovie
assetExport!.outputURL = movieDestinationUrl
assetExport!.videoComposition = layercomposition
self.movieUrl = movieFilePath
return assetExport!
}