Swift: Merge Videos back-to-back with AVAssetExportSession() - swift

Question

I have an array of video recordings stored as AVURLAsset and I want to merge the videos into 1 clip so that they play back to back with no time in-between videos. Below is what I'm hoping to do, but it is only showing the 1st video. Note: I want the videos to play back-to-back and without blank space between each. For example, if there is real time between recording1 and recording2 when the phone was not recording, the output should NOT show this.
Thanks for your help!
func mergeVideos(handler: #escaping (_ asset: AVAssetExportSession)->()) {
let mixComposition = AVMutableComposition()
var videoTime = CMTime.zero
for video in self.recordings {
let tracks = video.tracks(withMediaType: .video)
let videoTrack = tracks[0]
let videoTimeRange = CMTimeRangeMake(start: .zero, duration: video.duration)
guard let compositionVideoTrack: AVMutableCompositionTrack = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else { return }
do {
try compositionVideoTrack.insertTimeRange(videoTimeRange, of: videoTrack, at: videoTime)
videoTime = CMTimeAdd(videoTime, video.duration)
} catch {
print("An error occurred")
return
}
}
guard let documentDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
let dateFormatter = DateFormatter()
dateFormatter.dateStyle = .long
dateFormatter.timeStyle = .short
let date = dateFormatter.string(from: Date())
let url = documentDirectory.appendingPathComponent("mergeVideo-\(date).mov")
guard let exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality) else { return }
exporter.outputURL = url
exporter.outputFileType = AVFileType.mov
exporter.shouldOptimizeForNetworkUse = true
handler(exporter)
}

Answer 1

The solution is to move the AVMutableCompositionTrack outside of the for loop. My updated function to merge videos (with audio) is below. Hope this helps someone!
var recordings = [AVURLAsset]()
func mergeVideos(handler: #escaping (_ asset: AVAssetExportSession)->()) {
let videoComposition = AVMutableComposition()
var lastTime: CMTime = .zero
guard let videoCompositionTrack = videoComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else { return }
guard let audioCompositionTrack = videoComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else { return }
for video in self.recordings {
//add audio/video
do {
try videoCompositionTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: video.duration), of: video.tracks(withMediaType: .video)[0], at: lastTime)
try audioCompositionTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: video.duration), of: video.tracks(withMediaType: .audio)[0], at: lastTime)
} catch {
print("Failed to insert audio or video track")
return
}
//update time
lastTime = CMTimeAdd(lastTime, video.duration)
}
//create url
guard let documentDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
let dateFormatter = DateFormatter()
dateFormatter.dateStyle = .long
dateFormatter.timeStyle = .short
let date = dateFormatter.string(from: Date())
let url = documentDirectory.appendingPathComponent("mergeVideo-\(date).mov")
//export
guard let exporter = AVAssetExportSession(asset: videoComposition, presetName: AVAssetExportPresetHighestQuality) else { return }
exporter.outputURL = url
exporter.outputFileType = AVFileType.mp4
exporter.shouldOptimizeForNetworkUse = true
handler(exporter)
}