Swift - Compressing video files

So, at the moment I am using this to compress video:

func compressVideo(inputURL: NSURL, outputURL: NSURL, handler:(session: AVAssetExportSession)-> Void)
    {
        let urlAsset = AVURLAsset(URL: inputURL, options: nil)

        let exportSession = AVAssetExportSession(asset: urlAsset, presetName: AVAssetExportPresetMediumQuality)

        exportSession!.outputURL = outputURL

        exportSession!.outputFileType = AVFileTypeQuickTimeMovie

        exportSession!.shouldOptimizeForNetworkUse = true

        exportSession!.exportAsynchronouslyWithCompletionHandler { () -> Void in

            handler(session: exportSession!)
        }

    }

When I recorded a video in 2 seconds, the size was 4,3 MB and when I recorded a video in 6 seconds the file size was 9,3 MB.

Any tips to reduce the size?

This extension focuses on exporting it to a lower quality setting (in this case Medium) and uses an mp4 container, over the mov container favored by iOS. This can result in a loss of quality, but you can experiment with higher output settings and different formats as you work to fine tune your output.

extension PreviewVideoViewController: AVCaptureFileOutputRecordingDelegate {
    func fileOutput(_ output: AVCaptureFileOutput,
                    didFinishRecordingTo outputFileURL: URL,
                    from connections: [AVCaptureConnection],
                    error: Error?) {
        guard let data = try? Data(contentsOf: outputFileURL) else {
            return
        }

        print("File size before compression: \(Double(data.count / 1048576)) mb")

        let compressedURL = NSURL.fileURL(withPath: NSTemporaryDirectory() + UUID().uuidString + ".mp4")
        compressVideo(inputURL: outputFileURL as URL,
                      outputURL: compressedURL) { exportSession in
            guard let session = exportSession else {
                return
            }

            switch session.status {
            case .unknown:
                break
            case .waiting:
                break
            case .exporting:
                break
            case .completed:
                guard let compressedData = try? Data(contentsOf: compressedURL) else {
                    return
                }

                print("File size after compression: \(Double(compressedData.count / 1048576)) mb")
            case .failed:
                break
            case .cancelled:
                break
            }
        }
    }


    func compressVideo(inputURL: URL,
                       outputURL: URL,
                       handler:@escaping (_ exportSession: AVAssetExportSession?) -> Void) {
        let urlAsset = AVURLAsset(url: inputURL, options: nil)
        guard let exportSession = AVAssetExportSession(asset: urlAsset,
                                                       presetName: AVAssetExportPresetMediumQuality) else {
            handler(nil)

            return
        }

        exportSession.outputURL = outputURL
        exportSession.outputFileType = .mp4
        exportSession.exportAsynchronously {
            handler(exportSession)
        }
    }
}

   func convertVideo(phAsset : PHAsset){

    PHImageManager.default().requestAVAsset(forVideo: phAsset, options: PHVideoRequestOptions(), resultHandler: { (asset, audioMix, info) -> Void in
        if let asset = asset as? AVURLAsset {
            do {
                let videoData = try  Data.init(contentsOf: asset.url)
                print(asset.url)
                self.orginalVideo = asset.url
                print("File size before compression: \(Double(videoData.count / 1048576)) mb")
            let compressedURL = NSURL.fileURL(withPath: NSTemporaryDirectory() + NSUUID().uuidString + ".MP4")
                print(compressedURL)
                self.compressVideo(inputURL: asset.url , outputURL: compressedURL) { (exportSession) in
                    guard let session = exportSession else {
                        return
                    }
                    switch session.status {
                    case .unknown:
                        print("unknown")
                        break
                    case .waiting:
                        print("waiting")
                        break
                    case .exporting:
                        print("exporting")
                        break
                    case .completed:
                        do {
                        let compressedData = try  Data.init(contentsOf: compressedURL)
                            self.compressVideo = compressedURL
                            print(compressedData)
                             print("File size AFTER compression: \(Double(compressedData.count / 1048576)) mb")
                        }
                        catch{
                           print(error)
                        }


                    case .failed:
                        print("failed")
                        break
                    case .cancelled:
                        print("cancelled")
                        break
                    }
                }
            } catch {
                print(error)
                //return
            }
        }
    })


}

func compressVideo(inputURL: URL, outputURL: URL, handler:@escaping (_ exportSession: AVAssetExportSession?)-> Void) {
    let urlAsset = AVURLAsset(url: inputURL, options: nil)
    guard let exportSession = AVAssetExportSession(asset: urlAsset, presetName: AVAssetExportPresetMediumQuality) else {
        handler(nil)

        return
    }
    exportSession.outputURL = outputURL
    exportSession.outputFileType = AVFileType.mp4
    exportSession.shouldOptimizeForNetworkUse = true
    exportSession.exportAsynchronously { () -> Void in
        handler(exportSession)
    }
}