只需要开启画中画就可以后台写入了

import UIKit
import AVKit

class HomeVC: BaseViewController {
    var playerLayer: AVPlayerLayer?
    var pipPlayer: AVPlayer?
    var pipController: AVPictureInPictureController?
    
}

extension HomeVC: AVPictureInPictureControllerDelegate {
    func createPlayer() {
        // 加载视频
        guard let path = Bundle.main.path(forResource: "TEST", ofType: "mp4") else { return }
        // 加载视频
        let videoURL = URL(fileURLWithPath: path)
        let asset = AVAsset(url: videoURL)
        let playerItem = AVPlayerItem(asset: asset)
        pipPlayer = AVPlayer(playerItem: playerItem)
        
        // 创建视频播放器
        let playerLayer = AVPlayerLayer(player: pipPlayer)
        playerLayer.frame = CGRectMake(0, 0, screen_width * 0.4, screen_height * 0.4)
        self.playerLayer = playerLayer
        let videoPlayerView = UIView(frame: CGRectMake(0, screen_height * 0.3, screen_width * 0.4, screen_height * 0.4))
        videoPlayerView.layer.addSublayer(playerLayer)
        view.addSubview(videoPlayerView)
        videoPlayerView.isHidden = true
        
        if AVPictureInPictureController.isPictureInPictureSupported() {
            let session: AVAudioSession = AVAudioSession.sharedInstance()
            do {
                try session.setCategory(.playback, mode: .moviePlayback, options: [.interruptSpokenAudioAndMixWithOthers])
                try session.setActive(true)
            } catch  {
                print(error.localizedDescription)
            }
            pipController = AVPictureInPictureController(playerLayer: playerLayer)
            pipController?.delegate = self
        }
    }
    
    // 开始画中画
    func startPictureInPicture() {
        if AVPictureInPictureController.isPictureInPictureSupported() {
            pipController?.startPictureInPicture()
        }
    }
    
    // 开始画中画
    func endPictureInPicture() {
        pipController?.stopPictureInPicture()
    }

    
    // 实现画中画控制器的代理方法
    func pictureInPictureControllerWillStartPictureInPicture(_ pictureInPictureController: AVPictureInPictureController) {
        // 在开始画中画时，将视频暂停并隐藏播放器视图
        pipPlayer?.seek(to: .zero)
        pipPlayer?.play()
    }
    
    func pictureInPictureControllerDidStopPictureInPicture(_ pictureInPictureController: AVPictureInPictureController) {
        // 在结束画中画时，显示播放器视图并继续播放视频
        pipPlayer?.pause()
        scrollContent.slider_c?.isOn = false
        Defaults[\.SWAutoCopy] = false
    }
}