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我想将 AVAsset- 合并arrayVideos为一个视频并将其保存在相机胶卷中。Raywenderlich.com 有一个很棒的教程，其中两个视频合并为一个。我创建了以下代码，但是导出到相机胶卷后获得的视频仅包含数组中的第一个和最后一个视频（不包括中间的其余视频arrayVideos）。我在这里错过了什么吗？

var arrayVideos = [AVAsset]() //Videos Array    
var atTimeM: CMTime = CMTimeMake(0, 0)
var lastAsset: AVAsset!
var layerInstructionsArray = [AVVideoCompositionLayerInstruction]()
var completeTrackDuration: CMTime = CMTimeMake(0, 1)
var videoSize: CGSize = CGSize(width: 0.0, height: 0.0)

func mergeVideoArray(){

    let mixComposition = AVMutableComposition()
    for videoAsset in arrayVideos{
        let videoTrack = mixComposition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: Int32(kCMPersistentTrackID_Invalid))
        do {
            if videoAsset == arrayVideos.first{
                atTimeM = kCMTimeZero
            } else{
                atTimeM = lastAsset!.duration
            }
            try videoTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), of: videoAsset.tracks(withMediaType: …