merging videos together (AVFoundation)

Question

In my app, I\'m recording small videos and adding them into an NSMutableArray as AVAsset so that i keep record of what has been captured. when the user

Answer 1

updated @brenoxp's answer for Swift 5.1

func merge(arrayVideos:[AVAsset], completion:@escaping (URL?, Error?) -> ()) {

  let mainComposition = AVMutableComposition()
  let compositionVideoTrack = mainComposition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)
  compositionVideoTrack?.preferredTransform = CGAffineTransform(rotationAngle: .pi / 2)

  let soundtrackTrack = mainComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)

    var insertTime = CMTime.zero

  for videoAsset in arrayVideos {
    try! compositionVideoTrack?.insertTimeRange(CMTimeRangeMake(start: .zero, duration: videoAsset.duration), of: videoAsset.tracks(withMediaType: .video)[0], at: insertTime)
    try! soundtrackTrack?.insertTimeRange(CMTimeRangeMake(start: .zero, duration: videoAsset.duration), of: videoAsset.tracks(withMediaType: .audio)[0], at: insertTime)

    insertTime = CMTimeAdd(insertTime, videoAsset.duration)
  }

  let outputFileURL = URL(fileURLWithPath: NSTemporaryDirectory() + "merge.mp4")

  let fileManager = FileManager()
  try? fileManager.removeItem(at: outputFileURL)

  let exporter = AVAssetExportSession(asset: mainComposition, presetName: AVAssetExportPresetHighestQuality)

  exporter?.outputURL = outputFileURL
  exporter?.outputFileType = AVFileType.mp4
  exporter?.shouldOptimizeForNetworkUse = true

  exporter?.exportAsynchronously {
    if let url = exporter?.outputURL{
        completion(url, nil)
    }
    if let error = exporter?.error {
        completion(nil, error)
    }
  }
}