Add a Watermark on Video after merging Video and Audio Asset into one in Swift3 iOS

I am working on Video based application in Swift3. As per my requirement I have to merge Video and Audio AVAsset into one, adjust their volumes separately and save the final Video in iPhone Device gallery. This is working fine using below code:

func mergeVideoAndMusicWithVolume(assetVideo: AVAsset, assetMusic: AVAsset, startAudioTime: Float64, 
volumeVideo: Float, volumeAudio: Float){

        //To merging a video and a music and set it a volume
        let dirPaths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let docsDir = dirPaths[0] as String

        let composition: AVMutableComposition = AVMutableComposition()
        let compositionVideo: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: 
AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
        let compositionAudioVideo: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType:
 AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())
        let compositionAudioMusic: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: 
AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())

        //Add video to the final record
        do {
            try compositionVideo.insertTimeRange(CMTimeRangeMake(kCMTimeZero, assetVideo.duration), 
of: assetVideo.tracks(withMediaType: AVMediaTypeVideo)[0], at: kCMTimeZero)
        } catch _ {
        }

        //Extract audio from the video and the music
        let audioMix: AVMutableAudioMix = AVMutableAudioMix()
        var audioMixParam: [AVMutableAudioMixInputParameters] = []

        let assetVideoTrack: AVAssetTrack = assetVideo.tracks(withMediaType: AVMediaTypeAudio)[0]
        let assetMusicTrack: AVAssetTrack = assetMusic.tracks(withMediaType: AVMediaTypeAudio)[0]

        let videoParam: AVMutableAudioMixInputParameters = AVMutableAudioMixInputParameters(track: assetVideoTrack)
        videoParam.trackID = compositionAudioVideo.trackID

        let musicParam: AVMutableAudioMixInputParameters = AVMutableAudioMixInputParameters(track: assetMusicTrack)
        musicParam.trackID = compositionAudioMusic.trackID


        //Set final volume of the audio record and the music
        videoParam.setVolume(volumeVideo, at: kCMTimeZero)
        musicParam.setVolume(volumeAudio, at: kCMTimeZero)

        //Add setting
        audioMixParam.append(musicParam)
        audioMixParam.append(videoParam)

        //Add audio on final record
        //First: the audio of the record and Second: the music
        do {
            try compositionAudioVideo.insertTimeRange(CMTimeRangeMake(kCMTimeZero, 
assetVideo.duration), of: assetVideoTrack, at: kCMTimeZero)
        } catch _ {
            assertionFailure()
        }

        do {
            try compositionAudioMusic.insertTimeRange(CMTimeRangeMake(CMTimeMake(Int64(startAudioTime * 10000), 
10000), assetVideo.duration), of: assetMusicTrack, at: kCMTimeZero)
        } catch _ {
            assertionFailure()
        }

        //Add parameter
        audioMix.inputParameters = audioMixParam

        //Remove the previous temp video if exist
        let filemgr = FileManager.default
        do {
            if filemgr.fileExists(atPath: "\(docsDir)/movie-merge-music.mov") {
                try filemgr.removeItem(atPath: "\(docsDir)/movie-merge-music.mov")
            } else {
            }
        } catch _ {
        }

        //Exporte the final record’
        let completeMovie = "\(docsDir)/movie-merge-music.mov"
        let completeMovieUrl = NSURL(fileURLWithPath: completeMovie)
        let exporter: AVAssetExportSession = AVAssetExportSession(asset: composition, presetName:
 AVAssetExportPresetHighestQuality)!
        exporter.outputURL = completeMovieUrl as URL
        exporter.outputFileType = AVFileTypeMPEG4
        exporter.audioMix = audioMix

        exporter.exportAsynchronously(completionHandler: {
            DispatchQueue.main.async { _ in
                self.exportDidFinish(exporter)
            }
        })
    }


    func exportDidFinish(_ session: AVAssetExportSession) {
        if session.status == AVAssetExportSessionStatus.completed {
            let outputURL = session.outputURL

            PHPhotoLibrary.shared().performChanges({
                PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: outputURL!)
            }) { saved, error in
                if saved {
                    let alertController = UIAlertController(title: "Your video was successfully
 saved", message: nil, preferredStyle: .alert)
                    let defaultAction = UIAlertAction(title: "OK", style: .default, handler: nil)
                    alertController.addAction(defaultAction)
                    self.present(alertController, animated: true, completion: nil)
                }
            }
        }
    }

My Problem: Now I have to add a Watermark image on final Video before saving to Device gallery.
I checked Swift 3: How to add watermark on video ? AVVideoCompositionCoreAnimationTool iOS 10 issue but after applying Watermark, Video is coming in small area of frame size.
Can anyone help me how can I add the Watermark on my Video?


from Add a Watermark on Video after merging Video and Audio Asset into one in Swift3 iOS