如何在Swift中转换视频文件时设置最小输出大小？

let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetMediumQuality)
exportSession?.outputFileType = .mp4

let videoSettings: [String: Any] = [
    AVVideoCodecKey: AVVideoCodecType.h264,
    AVVideoWidthKey: 640,
    AVVideoHeightKey: 480,
    AVVideoCompressionPropertiesKey: [
        AVVideoAverageBitRateKey: 500000 // 设置比特率为500kbps
    ]
]
exportSession?.outputSettings = [
    AVVideoSettingsKey: videoSettings
]

import AVFoundation

func convertVideoWithMinOutputSize(inputURL: URL, outputURL: URL, minOutputSize: Int) {
    let asset = AVAsset(url: inputURL)
    let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetMediumQuality)
    exportSession?.outputFileType = .mp4

    let videoSettings: [String: Any] = [
        AVVideoCodecKey: AVVideoCodecType.h264,
        AVVideoWidthKey: 640,
        AVVideoHeightKey: 480,
        AVVideoCompressionPropertiesKey: [
            AVVideoAverageBitRateKey: minOutputSize
        ]
    ]
    exportSession?.outputSettings = [
        AVVideoSettingsKey: videoSettings
    ]

    exportSession?.exportAsynchronously(completionHandler: {
        switch exportSession?.status {
        case .completed:
            // 转换成功
            print("转换成功")
        case .failed:
            // 转换失败
            print("转换失败")
        case .cancelled:
            // 转换取消
            print("转换取消")
        default:
            break
        }
    })
}

// 使用示例
let inputURL = URL(fileURLWithPath: "input.mov")
let outputURL = URL(fileURLWithPath: "output.mp4")
let minOutputSize = 500000 // 500kbps
convertVideoWithMinOutputSize(inputURL: inputURL, outputURL: outputURL, minOutputSize: minOutputSize)