将视频的尺寸减小到指定的尺寸

Question

我想修剪视频并进行压缩，然后将文件上传到服务器，在服务器端，我的大小限制为25 MB，时间限制为1分钟。我正在使用PryntTrimmerView窗格最多将视频修剪一分钟，然后将修剪的视频压缩到25 MB。 我有用于压缩视频的代码，我在该主题中进行了很多搜索，但我找不到压缩视频的地方。 我测试了两个视频文件，它们分别是磁盘上的173.9 MB和34.6 MB。 现在压缩后173.9的大小减小到50.71，34.6减小到54.44，我不知道为什么34.6减小到54.44！如何将视频压缩到磁盘上的25 MG？ 有我的代码用于压缩视频并获取视频大小：

    func compress(fileName:String,videoPath : String, exportVideoPath : String, completion : @escaping (Bool) -> ()) {

        let videoUrl = URL(fileURLWithPath: videoPath)
        let videoAssetUrl = AVURLAsset(url: videoUrl)
        let videoTrackArray = videoAssetUrl.tracks(withMediaType: AVMediaTypeVideo)

        if videoTrackArray.count < 1 {
          completion(false)
          return
        }
        let videoAssetTrack = videoTrackArray[0]
        let audioTrackArray = videoAssetUrl.tracks(withMediaType: AVMediaTypeAudio)

        if audioTrackArray.count < 1 {
          completion(false)
          return
        }
        let outputUrl = URL(fileURLWithPath: exportVideoPath)
        var videoWriter = try? AVAssetWriter(url: outputUrl, fileType: AVFileTypeQuickTimeMovie)
        videoWriter?.shouldOptimizeForNetworkUse = true

        let vSetting = videoSettings(size: renderSize)
        let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: vSetting)
        videoWriterInput.expectsMediaDataInRealTime = false
        videoWriterInput.transform = videoAssetTrack.preferredTransform
        videoWriter?.add(videoWriterInput)


        let videoReaderSettings:[String : AnyObject] = [
          kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange) as AnyObject
        ]
        let videoReaderOutput = AVAssetReaderTrackOutput(track: videoAssetTrack, outputSettings: videoReaderSettings)
        let videoReader = try! AVAssetReader(asset: videoAssetUrl)
        videoReader.add(videoReaderOutput)
        videoWriter?.startWriting()
        videoReader.startReading()
        videoWriter?.startSession(atSourceTime: kCMTimeZero)

        let processingVideoQueue = DispatchQueue(label: "processingVideoCompressionQueue")
        videoWriterInput.requestMediaDataWhenReady(on: processingVideoQueue, using: {
          while(videoWriterInput.isReadyForMoreMediaData){
            let sampleVideoBuffer = videoReaderOutput.copyNextSampleBuffer()
            if (videoReader.status == .reading && sampleVideoBuffer != nil) {
              videoWriterInput.append(sampleVideoBuffer!)
            }else {
              videoWriterInput.markAsFinished()
              if (videoReader.status == .completed) {

                videoWriter?.finishWriting(completionHandler: {
                  videoWriter = nil
                  self.export = true
                  completion(true)

                })
              }
            }
            if self.export {
              break
            }
          }
        })
      }

 func videoSettings() -> [String : AnyObject] {

    var compressionSettings = [String : AnyObject]()
    //    compressionSettings[AVVideoAverageBitRateKey] = 425000
    compressionSettings[AVVideoAverageBitRateKey] = 1 as AnyObject
    compressionSettings[AVVideoProfileLevelKey] = AVVideoProfileLevelH264Main30 as AnyObject;
    compressionSettings[AVVideoMaxKeyFrameIntervalKey] = 1 as AnyObject
    var settings = [String : AnyObject]()
    settings[AVVideoCompressionPropertiesKey] = compressionSettings as AnyObject
    settings[AVVideoCodecKey] = AVVideoCodecH264 as AnyObject?
    settings[AVVideoHeightKey] = 500 as AnyObject?
    settings[AVVideoWidthKey] = 720 as AnyObject?

    return settings
  }

func getFileSize() {
    var fileSize : UInt64
    do {
      let attr:NSDictionary? = try FileManager.default.attributesOfItem(atPath: path) as NSDictionary
    if let _attr = attr {
      fileSize = _attr.fileSize();
      print(fileSize)
      var sizeMB = Double(fileSize / 1024)
      sizeMB = Double(sizeMB / 1024)
      print(String(format: "%.2f", sizeMB) + " MB")
      if sizeMB > 25 {
        showVideoWrongSizeAlert()
        return
      }
    }
    }catch {
      print(error.localizedDescription)
    }