Estoy usando el siguiente método para descargar y guardar mi video en la galería, con .mp4 funciona normalmente, pero cuando se cambia a .m3u8 siempre falla.

func downloadVideoLinkAndCreateAsset(_ videoLink: String,_ fileName : String) {

        // use guard to make sure you have a valid url
        guard let videoURL = URL(string: videoLink) else { return }

        guard let documentsDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
        let fileNameToSave = "CiviX_HistoryVideo_\(fileName)"
        // check if the file already exist at the destination folder if you don't want to download it twice
        if !FileManager.default.fileExists(atPath: documentsDirectoryURL.appendingPathComponent(fileNameToSave).path) {

            // set up your download task
            URLSession.shared.downloadTask(with: videoURL) { (location, response, error) -> Void in

                // use guard to unwrap your optional url
                guard let location = location else { return }

                // create a deatination url with the server response suggested file name
                let destinationURL = documentsDirectoryURL.appendingPathComponent(fileNameToSave)
                print("destinationURL: \(destinationURL)")
                do {

                    try FileManager.default.moveItem(at: location, to: destinationURL)

                    PHPhotoLibrary.requestAuthorization({ (authorizationStatus: PHAuthorizationStatus) -> Void in

                        // check if user authorized access photos for your app
                        if authorizationStatus == .authorized {
                            PHPhotoLibrary.shared().performChanges({
                                PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: destinationURL)}) { completed, error in
                                    if completed {
                                        print("Video asset created")
                                    } else {
                                        print("Video asset create failed: \(error?.localizedDescription)")
                                    }
                            }
                        }
                    })

                } catch { print("file manager error: \(error.localizedDescription)") }

                }.resume()

        } else {
            print("File already exists at destination url")
        }

    }

then aquí hay un método para llamar a

let urlString = response.replacingOccurrences(of: "\"", with: "") -> my m3u8 URL

let videoImageUrl = "https://www.sample-videos.com/video123/mp4/720/big_buck_bunny_720p_1mb.mp4" -> always success

//TEST MP4 file -> ALWAYS SUCCESS
self.downloadVideoLinkAndCreateAsset(videoImageUrl, "big_buck_bunny_720p_1mb.mp4")

//TEST M3U8 FIlE -> FAIL
self.downloadVideoLinkAndCreateAsset(urlString, history.fileName!) -> fileName format is 'abc.mp4'

El resultado del registro para MP4

destinationURL: archivo: /// Users / thehe / Library / Developer / CoreSimulator / Devices / 05C6DE76-6609-4E4A-B00D-2CE3622D2EF8 / data / Containers / Data / Application / 90994674-6C07-47F9-A880-D1A80CDA0C27 / Documents / CiviX_HistoryVideo_big_buck_bunny_720p_1mb.mp4

-> Elemento de video creado

El resultado del registro para M3U8

self.downloadVideoLinkAndCreateAsset (urlString, history.fileName!)

destinationURL: archivo: /// Users / thehe / Library / Developer / CoreSimulator / Devices / 05C6DE76-6609-4E4A-B00D-2CE3622D2EF8 / data / Containers / Data / Application / DA6ABC38-4E0A-44C7-9C56-8B65F1DC0D4D / Documents / CiviX_HistoryVideo_20-1-2019_3h18m32s.mp4

-> Error al crear un recurso de video: Opcional ("La operación no se pudo completar. (Error de cacao -1.)")

Traté de guardar con la extensión .m3u8 pero aún no funciona

self.downloadVideoLinkAndCreateAsset (urlString, "TEST_M3U8_FILE.m3u8")

destinationURL: archivo: /// Users / thehe / Library / Developer / CoreSimulator / Devices / 05C6DE76-6609-4E4A-B00D-2CE3622D2EF8 / data / Containers / Data / Application / 9B42A55B-4E3E-4A20-A0DC-6E1ED22471A2 / Documents / CiviX_HistoryVideo_TEST_M3U8_FILE.m3u8

-> Error al crear un recurso de video: Opcional ("La operación no se pudo completar. (Error de cacao -1.)")