如何在Swift中录制视频时添加覆盖？

import AVFoundation
import UIKit

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {
    var captureSession: AVCaptureSession?
    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    var movieOutput: AVCaptureMovieFileOutput?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建AVCaptureSession对象
        captureSession = AVCaptureSession()
        
        // 获取摄像头设备
        guard let captureDevice = AVCaptureDevice.default(for: .video) else { return }
        
        do {
            // 创建输入对象
            let input = try AVCaptureDeviceInput(device: captureDevice)
            
            // 将输入对象添加到会话
            captureSession?.addInput(input)
            
            // 创建预览图层
            videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
            videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
            videoPreviewLayer?.frame = view.layer.bounds
            
            // 将预览图层添加到视图中
            view.layer.addSublayer(videoPreviewLayer!)
            
            // 创建输出对象
            movieOutput = AVCaptureMovieFileOutput()
            
            // 将输出对象添加到会话
            captureSession?.addOutput(movieOutput!)
            
            // 开始会话
            captureSession?.startRunning()
            
            // 设置视频输出代理
            let videoOutput = AVCaptureVideoDataOutput()
            videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue.main)
            captureSession?.addOutput(videoOutput)
        } catch {
            print(error)
        }
    }
    
    // 视频帧处理代理方法
    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        // 处理视频帧数据
        if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
            // 在视频帧上添加覆盖效果
            let overlayImage = UIImage(named: "overlay.png")
            let overlayImageView = UIImageView(image: overlayImage)
            overlayImageView.frame = CGRect(x: 0, y: 0, width: CVPixelBufferGetWidth(imageBuffer), height: CVPixelBufferGetHeight(imageBuffer))
            
            // 将覆盖视图绘制到视频帧上
            UIGraphicsBeginImageContext(CGSize(width: CVPixelBufferGetWidth(imageBuffer), height: CVPixelBufferGetHeight(imageBuffer)))
            overlayImageView.layer.render(in: UIGraphicsGetCurrentContext()!)
            let overlayImageWithGraphics = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            
            // 将视频帧写入输出对象
            if let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
                let ciImage = CIImage(cvPixelBuffer: pixelBuffer)
                let context = CIContext()
                context.render(overlayImageWithGraphics!.ciImage!, to: ciImage, bounds: ciImage.extent, colorSpace: ciImage.colorSpace!)
                
                // 将处理后的视频帧写入输出对象
                movieOutput?.append(sampleBuffer)
            }
        }
    }
    
    // 开始录制
    func startRecording() {
        let outputPath = NSTemporaryDirectory() + "output.mov"
        let outputFileURL = URL(fileURLWithPath: outputPath)
        movieOutput?.startRecording(to: outputFileURL, recordingDelegate: self)
    }
    
    // 停止录制
    func stopRecording() {
        movieOutput?.stopRecording()
    }
}