import UIKit
import AVFoundation

class ViewController: UIViewController {

var asset: AVAsset?

override func viewDidLoad() {
super.viewDidLoad()

let videoAsset = AVURLAsset(url: Bundle.main.url(forResource: "BabyImSorry", withExtension: "m4v")!)
let audioAsset1 = AVURLAsset(url: Bundle.main.url(forResource: "BabyImSorry", withExtension: "m4v")!)
let comp = AVMutableComposition()
let videoAssetSourceTrack = videoAsset.tracks(withMediaType: AVMediaTypeVideo).first! as AVAssetTrack
let videoCompositionTrack = comp.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
let audioAssetSourceTrack1 = audioAsset1.tracks(withMediaType: AVMediaTypeAudio).first! as AVAssetTrack
let audioCompositionTrack = comp.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)

do {

try videoCompositionTrack.insertTimeRange(
CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(15, 600)),
of: videoAssetSourceTrack,
at: kCMTimeZero)

try audioCompositionTrack.insertTimeRange(
CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(15, 600)),
of: audioAssetSourceTrack1,
at: kCMTimeZero)

}catch { print(error) }

asset = comp
}

override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}

func createAudioFileFromAsset(_ asset: AVAsset){

let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0] as URL

let filePath = documentsDirectory.appendingPathComponent("rendered-audio.m4v")
//deleteFile(filePath)

if let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPreset640x480){

exportSession.canPerformMultiplePassesOverSourceMediaData = true
exportSession.outputURL = filePath
exportSession.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration)
exportSession.outputFileType = AVFileTypeQuickTimeMovie
exportSession.exportAsynchronously {
_ in
print("finished: \(filePath) : \(exportSession.status.rawValue) ")
}
}
}

@IBAction func saveVideo(_ sender: Any) {

guard let asset = asset else {
return
}

createAudioFileFromAsset(asset)
}

}