如何在swift中修改下载后的视频格式

import AVFoundation

let fileURL = URL(fileURLWithPath: "path_to_downloaded_video")

let asset = AVAsset(url: fileURL)

let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetPassthrough)
exportSession?.outputFileType = .mp4 // 设置输出文件格式为MP4，可以根据需求修改为其他格式

let outputURL = URL(fileURLWithPath: "path_to_output_video")
exportSession?.outputURL = outputURL

exportSession?.exportAsynchronously(completionHandler: {
    switch exportSession?.status {
    case .completed:
        // 导出成功
        print("视频格式修改成功")
    case .failed:
        // 导出失败
        print("视频格式修改失败")
    case .cancelled:
        // 导出取消
        print("视频格式修改取消")
    default:
        break
    }
})