How to create many audio track item with different start time?

[duylinh]

I want to build application add multi music to video. I have a video track item and some audio track item. I need to misc some audio track (with different start time) and video. Ref: I have referenced on page --> https://github.com/vitoziv/VideoCat Example: video: ___[=======================] video track audios : [--------===========] audio track 1 ____[-----========] audio track 2 __[=======================--------] audio track 3 ____[-------------=======================---------] audio track 4 Note: ====== : available -------- : unavailable

video: __[=======================] video track audio track 1:[~~~~===========] offsetTime < 0 audio track 2:____~~~~[===========] offsetTime > 0 ==> ~ : offsetTime

     video__:[========================60s===================] total
     result: 60s --> 20s with lowtime 20s, uptime 40s
     trimed_:[[-----20s-----][======20s=====][______20s_____]
     trimed_:[[+++++++++++++++++++++++++++++]
     ==> [----] lowtime
     ==> [+++] up time

   convenience init --> AudioData :
    self.offsetTime = offsetTime
    self.lowTime = lowTime > 0.0 ? lowTime : 0.0
    let upValue = max(upTime, lowTime)
    self.upTime = upValue
    let durationValue = upValue - lowTime
    self.duration = durationValue
    let startTime = lowTime + offsetTime
    self.startTime = startTime
    let distance = min(durationValue, videoDuration)
    let available = distance - startTime
    self.available = available

My code: Video track item:

let asset = AVAsset(url: url) let resource = AVAssetTrackResource(asset: asset) let lowTime = CMTime(seconds: video.lowTime, preferredTimescale: 600) //default lowtime = 0.0 let durationTime = CMTime(seconds: video.duration, preferredTimescale: 600) //default video.duration = total time of video resource.selectedTimeRange = CMTimeRange(start: CMTime.zero, duration: durationTime) let videoTrackItem = TrackItem(resource: resource) videoTrackItem.startTime = lowTime videoTrackItem.videoConfiguration.contentMode = .aspectFill videoTrackItem.audioConfiguration.volume = video.volume

    context.viewModel.addVideoTrackItem(videoTrackItem)
    context.videoView.player.replaceCurrentItem(context.viewModel.playerItem)
    context.timelineView.reload(with: context.viewModel.videoTrackItems)

A Audio track item:

let asset = AVAsset(url: url) let resource = AVAssetTrackResource(asset: asset)

    print("lowtime \(audio.lowTime)") // default low time = 0.0
    print("upTime \(audio.upTime)")
    print("startTime \(audio.startTime)")
    print("available \(audio.available)")
    print("videoDuration \(self.durationTimeOfVideo)")

    let startTime = CMTime(seconds: audio.startTime, preferredTimescale: 600)
    let availableTime = CMTime(seconds: audio.available, preferredTimescale: 600)

    resource.selectedTimeRange = CMTimeRange(start: CMTime.zero, duration: availableTime)
    let trackItem = TrackItem(resource: resource)
    trackItem.startTime = startTime
    trackItem.audioConfiguration.volume = audio.volume

TimelineViewModel

class TimelineManager { static let current = TimelineManager() var timeline = Timeline() }

 class TimelineViewModel {

      // MARK: - Vars
     private(set) var audioTrackItems = [TrackItem]()
     private(set) var videoTrackItems = [TrackItem]()
     private(set) var renderSize: CGSize = CGSize.zero
     private(set) var lut: String = "original_lut"
     private(set) var playerItem = AVPlayerItem(asset: AVComposition())

    func buildTimeline() -> Timeline {
           let timeline = TimelineManager.current.timeline
           reloadTimeline(timeline)
           return timeline
    }

    // MARK: - Add/Replace

    func addVideoTrackItem(_ trackItem: TrackItem) {
           videoTrackItems.append(trackItem)
           reloadPlayerItems()
    }

    func insertTrackItem(_ trackItem: TrackItem, at index: Int) {
         guard audioTrackItems.count >= index else { return }
         audioTrackItems.insert(trackItem, at: index)
         reloadPlayerItems()
    }

   func updateTrackItem(_ trackItem: TrackItem, at index: Int) {
       guard audioTrackItems.count > index else { return }
       audioTrackItems[index] = trackItem
       reloadPlayerItems()
  }

   func removeTrackItem(_ trackItem: TrackItem) {
        guard let index = audioTrackItems.index(of: trackItem) else { return }
        audioTrackItems.remove(at: index)
        reloadPlayerItems()
   }

   func removeTrackItem(at index: Int) {
         guard audioTrackItems.count > index else { return }
         audioTrackItems.remove(at: index)
         reloadPlayerItems()
   }

   func removeAllAudioTrackItems() {
        audioTrackItems.removeAll()
        reloadPlayerItems()
  }

  func removeAll() {
       audioTrackItems.removeAll()
       videoTrackItems.removeAll()
       reloadPlayerItems()
  }

   func reloadPlayerItems() {
          let timeline = TimelineManager.current.timeline
          timeline.renderSize = renderSize
         reloadTimeline(timeline)
         do {
               try Timeline.reloadVideoStartTime(providers: videoTrackItems)
         } catch {
              assert(false, error.localizedDescription)
         }
         build(with: timeline)
     }

   fileprivate func build(with timeline: Timeline) {
         let compositionGenerator = CompositionGenerator(timeline: timeline)
        let playerItem = compositionGenerator.buildPlayerItem()
        self.playerItem = playerItem
   }

   fileprivate func reloadTimeline(_ timeline: Timeline) {
        timeline.videoChannel = videoTrackItems
        timeline.audios = videoTrackItems + audioTrackItems
   }

 extension TrackItem {
       func reloadTimelineDuration() {
            self.duration = self.resource.selectedTimeRange.duration
       }
}

==> Errors:

• When offsettime < 0: video: __[=======================] video track audio track:___[~~~~~===========] offsetTime < 0 --> audio track play incorrect starttime