Question

我试图覆盖M4A文件中曲目编号元数据的值。当我从现有轨道中读取值时：

if metadataIdentifier == AVMetadataIdentifier.iTunesMetadataTrackNumber{
   print(track Number = \(itunesMetadata.value?.description)")
}

我得到了

track Number = <00000008 000E>

哪个结果是曲目编号 00000008 的十六进制表示以及总曲目 000E

通过做出这个假设，我试着像这样编写这个标签：

    let trackNumber = String(format:"%08X", editedTrack?.trackNumber ?? 0)
    let totalTrackNumber = String(format:"%04X", editedTrack?.totalTrackNumber ?? 0)
    let trackNumberValue = "<\(dikNumber) \(totalDiskNumber)>"

    let avMetaTrack = AVMutableMetadataItem()
    avMetaTrack.keySpace = AVMetadataKeySpace.iTunes
    avMetaTrack.key = AVMetadataIdentifier.iTunesMetadataTrackNumber as NSCopying & NSObjectProtocol
    avMetaTrack.identifier = AVMetadataIdentifier.iTunesMetadataTrackNumber

    avMetaTrack.value = trackNumberData as NSCopying & NSObjectProtocol

但它在itunes和外部标签编辑器中都不起作用。

编辑：然后我通过

转换成新文件

/* Export Metadata */
        let urlAsset = AVURLAsset.init(url: trackFileManager.documentsUrl.appendingPathComponent(trackToEdit?.url ?? ""))

        let assetExportSession: AVAssetExportSession! = AVAssetExportSession(asset: urlAsset, presetName: AVAssetExportPresetPassthrough)
        assetExportSession.outputFileType = AVFileType.m4a
        let stringUrlPath:[String] = (trackToEdit?.url?.components(separatedBy: "/"))!
        assetExportSession.outputURL = trackFileManager.documentsUrl.appendingPathComponent("ex_\(stringUrlPath.last!)")
        assetExportSession.metadata = newMetadata

        print("\(logClassNameChild): output = \(assetExportSession.outputURL!)")

        assetExportSession.exportAsynchronously(completionHandler: {
            print("done")
            //try! FileManager.default.removeItem(atPath: documentsUrl.appendingPathComponent(trackObject.url!).path)
            //try! FileManager.default.moveItem(at: assetExportSession.outputURL!, to: documentsUrl.appendingPathComponent(trackObject.url!))
        })

Answer 1

事实证明，根据预期，数据需要像这样读取和写入

        if metadataIdentifier == AVMetadataIdentifier.iTunesMetadataTrackNumber{

            if let trackMetadataData = itunesMetadata.value as? Data{

                let trackMetadataByteArray = [UInt8](trackMetadataData)

                /*[0, 0, 0, 4, 0, 14, 0, 0]*/
                if trackMetadataByteArray.count == 8{
                    print("\(logClassName):  getItunesMetadata -> Track Number \(trackMetadataByteArray)")

                    /*Get track number -> Bytes 2,3*/
                    var trackArray = Array(trackMetadataByteArray[2...3])
                    let trackData = Data(bytes: &trackArray, count: 2)
                    tracKNumber = Int(Int16(bigEndian: trackData.withUnsafeBytes { $0.pointee }))


                    /*Get track total -> Bytes 4,5*/
                    var trackTotalArray = Array(trackMetadataByteArray[4...5])
                    let trackTotalData = Data(bytes: &trackTotalArray, count: 2)
                    totalTrack = Int(Int16(bigEndian: trackTotalData.withUnsafeBytes { $0.pointee }))

                }
                else{
                    print("\(logClassName): Error: Wrong track format")
                }

            }
            else{
                print("\(logClassName): Error: Wrong track format")
            }

在另一个写作网站上：

var trackNumberByteArray = [UInt8]()

    trackNumberByteArray.append(contentsOf: MetadataItem.int16ToByteArray(number: Int16(0)))
    trackNumberByteArray.append(contentsOf: MetadataItem.int16ToByteArray(number: Int16(editedTrack?.trackNumber ?? 0)))
    trackNumberByteArray.append(contentsOf: MetadataItem.int16ToByteArray(number: Int16(editedTrack?.totalTrackNumber ?? 0)))
    trackNumberByteArray.append(contentsOf: MetadataItem.int16ToByteArray(number: Int16(0)))

    let trackNumberData = Data(bytes: trackNumberByteArray)
    print("MetadataItem: \(trackNumberData)")

    let avMetaTrack = AVMutableMetadataItem()
    avMetaTrack.keySpace = AVMetadataKeySpace.iTunes
    avMetaTrack.key = AVMetadataIdentifier.iTunesMetadataTrackNumber as NSCopying & NSObjectProtocol
    avMetaTrack.identifier = AVMetadataIdentifier.iTunesMetadataTrackNumber

    avMetaTrack.value = trackNumberData as NSCopying & NSObjectProtocol

修改iTunesMetadataTrackNumber音频文件M4A swift

1 个答案: