AVFoundation -Videos合并，但仅播放最后一个视频

import AVFoundation

let composition = AVMutableComposition()

let videoTrack = composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)

let assetTrack = asset.tracks(withMediaType: .video).first

try? videoTrack?.insertTimeRange(CMTimeRangeMake(start: .zero, duration: asset.duration), of: assetTrack!, at: composition.duration)

let videoComposition = AVMutableVideoComposition()
videoComposition.renderSize = CGSize(width: videoTrack!.naturalSize.width, height: videoTrack!.naturalSize.height)

let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(start: .zero, duration: composition.duration)

let layerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack!)
layerInstruction.setTransform(videoTrack!.preferredTransform, at: .zero)

instruction.layerInstructions = [layerInstruction]

videoComposition.instructions = [instruction]

let playerItem = AVPlayerItem(asset: composition)
playerItem.videoComposition = videoComposition

let player = AVPlayer(playerItem: playerItem)

let playerLayer = AVPlayerLayer(player: player)
playerLayer.frame = view.bounds
view.layer.addSublayer(playerLayer)

player.play()