Sam Sam - 1 year ago 148
Swift Question

Swift 3 : issue with AVVideoCompositionCoreAnimationTool to add watermark on video

The following code was working perfectly to add a logo and a text to a video with AVVideoCompositionCoreAnimationTool. Then Swift 3 came! Now sometimes the video shows with the logo and text sometimes the video does not show when it is exported.

let videoComposition: AVMutableVideoComposition = AVMutableVideoComposition()

videoComposition.frameDuration = CMTimeMake(1, 60)
videoComposition.renderSize = CGSize(width: clipVideoTrack.naturalSize.height, height: clipVideoTrack.naturalSize.height)

let instruction: AVMutableVideoCompositionInstruction = AVMutableVideoCompositionInstruction()

instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(60, 30))

// transformer is applied to set the video in portrait otherwise it is rotated by 90 degrees
let transformer: AVMutableVideoCompositionLayerInstruction =
AVMutableVideoCompositionLayerInstruction(assetTrack: clipVideoTrack)

let t1: CGAffineTransform = CGAffineTransform(translationX: clipVideoTrack.naturalSize.height, y: -(clipVideoTrack.naturalSize.width - clipVideoTrack.naturalSize.height)/2)

let t2: CGAffineTransform = t1.rotated(by: CGFloat(M_PI_2))

var finalTransform: CGAffineTransform = t2

transformer.setTransform(finalTransform, at: kCMTimeZero)

instruction.layerInstructions = NSArray(object: transformer) as! [AVVideoCompositionLayerInstruction]

videoComposition.instructions = NSArray(object: instruction) as! [AVVideoCompositionInstructionProtocol]

let mixComposition = AVMutableComposition()
let compositionVideoTrack = mixComposition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)

do {
try compositionVideoTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, asset.duration), of: clipVideoTrack, at: kCMTimeZero)
} catch {

//Add watermark

let myImage = UIImage(named: "logo")

let aLayer = CALayer()
aLayer.contents = myImage!.cgImage
aLayer.frame = CGRect(x: (clipVideoTrack.naturalSize.height*(self.view.bounds.width-45))/self.view.bounds.width, y: (clipVideoTrack.naturalSize.height*(self.view.bounds.width-40))/self.view.bounds.width, width: (clipVideoTrack.naturalSize.height*40)/self.view.bounds.width, height: (clipVideoTrack.naturalSize.height*40)/self.view.bounds.width)

let titleLayer = CATextLayer()
titleLayer.string = "text"
titleLayer.font = UIFont(name: "helvetica", size: 0)
titleLayer.fontSize = clipVideoTrack.naturalSize.height/16
titleLayer.shadowOpacity = 0.5
titleLayer.alignmentMode = kCAAlignmentCenter
titleLayer.frame = CGRect(x: 0, y: 0, width: clipVideoTrack.naturalSize.height, height: clipVideoTrack.naturalSize.height/6)

let videoSize = asset.tracks(withMediaType: AVMediaTypeVideo)[0].naturalSize
let parentLayer = CALayer()
let videoLayer = CALayer()
parentLayer.frame = CGRect(x: 0, y: 0, width: videoSize.height, height: videoSize.height)
videoLayer.frame = CGRect(x: 0, y: 0, width: videoSize.height, height: videoSize.height)


videoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)

do { try FileManager.default.removeItem(at: filePath) }
catch let error as NSError {
NSLog("\(error), \(error.localizedDescription)")

var exportUrl: URL = filePath
self.videoUrl = filePath as NSURL

var exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetMediumQuality)

exporter!.videoComposition = videoComposition
exporter!.outputFileType = AVFileTypeQuickTimeMovie
exporter!.outputURL = URL(fileURLWithPath: exportUrl.path)

exporter!.exportAsynchronously(completionHandler: {

DispatchQueue.main.async {


let item = AVPlayerItem(url: exportUrl)
self.player.replaceCurrentItem(with: item)

if (self.player.currentItem != nil) {
print("Starting playback!")



This was working flawlessly with previous version of Swift but now with swift 3 not working anymore.

PLEASE NOTE: if I comment out
videoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)
then the video is exported and plays successfully overtime but without any overlay.

Answer Source

Seeing as the code works on iOS 9, this is probably a bug in iOS 10.0 where AVAssetExportSessions don't work properly when they have videoComposition set.

Some have reported that things look better in the iOS 10.1 beta and others have worked around the problem.