AVMutableComposition somehow exports portrait video to landscape orientation - ios

Question

This function is exporting the merged composition to a landscape orientation when the source video is in portrait. I save the original video in portrait orientation to my documents directory and then save it to camera roll and works fine. I then pass the saved video's url to this function and it somehow rotates it to landscape when it shouldn't. How do I fix this?
func makeVideoOverlay (url : URL) {
print("documents directory url: \(url)")
let composition = AVMutableComposition()
let vidAsset = AVURLAsset(url: url as URL, options: nil)
// get video track
let vtrack = vidAsset.tracks(withMediaType: AVMediaTypeVideo)
let videoTrack:AVAssetTrack = vtrack[0]
let vid_duration = videoTrack.timeRange.duration
let vid_timerange = CMTimeRangeMake(kCMTimeZero, vidAsset.duration)
//var error: NSError?
let compositionvideoTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
do {
try compositionvideoTrack.insertTimeRange(vid_timerange, of: videoTrack, at: kCMTimeZero)
} catch {
// handle error
print("comp video track error: \(error.localizedDescription)")
}
compositionvideoTrack.preferredTransform = videoTrack.preferredTransform
let size = videoTrack.naturalSize
//this prints out to 1920x1080 landscape dimension. i don't know how
print("asset size: \(size)")
// Watermark Effect
let imglogo = UIImage(named: "logo-image")
let imglayer = CALayer()
imglayer.contents = imglogo?.cgImage
imglayer.frame = CGRect.init(x: 5, y: size.height-160, width: 150, height: 150)
imglayer.opacity = 1.0
let videolayer = CALayer()
videolayer.frame = CGRect.init(x: 0, y: 0, width: size.width, height: size.height)
let parentlayer = CALayer()
parentlayer.frame = CGRect.init(x: 0, y: 0, width: size.width, height: size.height)
parentlayer.addSublayer(videolayer)
parentlayer.addSublayer(imglayer)
let layercomposition = AVMutableVideoComposition()
layercomposition.frameDuration = CMTimeMake(1, 30)
layercomposition.renderSize = size
layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)
// instruction for watermark
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
let videotrack = composition.tracks(withMediaType: AVMediaTypeVideo)[0] as AVAssetTrack
let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
instruction.layerInstructions = NSArray(object: layerinstruction) as [AnyObject] as [AnyObject] as! [AVVideoCompositionLayerInstruction]
layercomposition.instructions = NSArray(object: instruction) as [AnyObject] as [AnyObject] as! [AVVideoCompositionInstructionProtocol]
// create new file to receive data
let dirPaths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let docsDir: String = dirPaths[0] as String
let movieFilePath = docsDir.appending("/result.mov") as String
movieDestinationUrl = URL(fileURLWithPath: movieFilePath)
print("overlay destination url: \(movieDestinationUrl)")
// use AVAssetExportSession to export video
let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality)
assetExport?.outputFileType = AVFileTypeQuickTimeMovie
assetExport?.outputURL = movieDestinationUrl as URL
assetExport?.videoComposition = layercomposition
assetExport?.exportAsynchronously(completionHandler: {
if assetExport?.status == AVAssetExportSessionStatus.failed
{
print("failed: \(assetExport?.error)")
}
else if assetExport?.status == AVAssetExportSessionStatus.cancelled
{
print("cancelled: \(assetExport?.error)")
}
else
{
print("Movie complete")
OperationQueue.main.addOperation({ () -> Void in
//saves in landscape
self.saveAsset(url: self.movieDestinationUrl)
})
}
})
}

Answer 1

AVMutableVideoCompositionLayerInstruction has a method setTransform(_:at:)
As documentation say
Sets a fixed transform to apply from the specified time until the next
time at which a transform is set. [...]. Before the first specified time for which a
transform is set, the affine transform is held constant at the value
of identity ; after the last time for which a transform is set, the
affine transform is held constant at that last value.
You should set videoTrack's preferredTransform to layerInstruction instead.
EDIT
You need to create layerinstruction with the new created composition track instead.
let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: compositionvideoTrack) // NOT videoTrack.
layerinstruction.setTransform(videoTrack.preferredTransform, at: kCMTimeZero)