android - 如何获取和修改元数据以支持 Android 上的音频文件？

Question

背景

Android 支持various audio files编码和解码。

我使用 android.media.MediaRecorder 将音频录制到音频文件中 类，但我也希望显示有关我记录的文件的信息(不是标准数据，但仍然只是文本，甚至可能由用户配置)，我认为最好将此信息存储在文件中。

可能要存储的数据示例:记录的时间、记录的位置、用户的注释...

问题

MediaRecorder 类没有任何我能找到的功能，无法添加甚至读取录制的音频文件的元数据。

我也找不到类似的类(class)。

我尝试过的

我尝试搜索如何针对特定文件类型执行此操作，还尝试找到一个可以执行此操作的库。

我什至没有找到关于此信息的线索。

我为 MediaRecorder 类找到的唯一东西是一个名为“setLocation”的函数，它用于指示录制开始的位置(地理上)，查看它的代码，我可以看到它设置参数:

public void setLocation(float latitude, float longitude) {
    int latitudex10000  = (int) (latitude * 10000 + 0.5);
    int longitudex10000 = (int) (longitude * 10000 + 0.5);

    if (latitudex10000 > 900000 || latitudex10000 < -900000) {
        String msg = "Latitude: " + latitude + " out of range.";
        throw new IllegalArgumentException(msg);
    }
    if (longitudex10000 > 1800000 || longitudex10000 < -1800000) {
        String msg = "Longitude: " + longitude + " out of range";
        throw new IllegalArgumentException(msg);
    }

    setParameter("param-geotag-latitude=" + latitudex10000);
    setParameter("param-geotag-longitude=" + longitudex10000);
}

但是 setParameter 是私有(private)的，我不确定是否可以将我想要的任何东西放入其中，即使我有办法访问它(例如反射):

private native void setParameter(String nameValuePair);

对于给定的音频/视频文件，我也不知道如何获取/修改此类信息。它不适用于 SimpleExoPlayer ，例如。

问题

1. 如何读取、写入和修改 Android 支持的音频文件中的元数据？

2. 这些操作是否有任何限制？

3. 哪些文件格式适用于此？

4. 是否可以在录制音频时添加元数据？

5. 是否可以通过 MediaStore 实现？但是我该怎么做这些操作呢？支持哪些文件？元数据是否保留在文件中？

---

编辑:好的，我已经查看了提供给我的解决方案( here ， repo here ，基于 here )，它似乎运行良好。但是，它不适用于它使用的最新版本的库(org.mp4parser.isoparser:1.9.37 mp4parser 的依赖项)，所以我留下这个问题有待回答:为什么它不适用于该库的最新版本吗？

代码:

object MediaMetaDataUtil {
    interface PrepareBoxListener {
        fun prepareBox(existingBox: Box?): Box
    }

    @WorkerThread
    fun <T : Box> readMetadata(mediaFilePath: String, boxType: String): T? {
        return try {
            val isoFile = IsoFile(FileDataSourceImpl(FileInputStream(mediaFilePath).channel))
            val nam = Path.getPath<T>(isoFile, "/moov[0]/udta[0]/meta[0]/ilst/$boxType")
            isoFile.close()
            nam
        } catch (e: Exception) {
            null
        }
    }

    /**
     * @param boxType the type of the box. Example is "©nam" (AppleNameBox.TYPE). More available here: https://kdenlive.org/en/project/adding-meta-data-to-mp4-video/
     * @param listener used to prepare the existing or new box
     * */
    @WorkerThread
    @Throws(IOException::class)
    fun writeMetadata(mediaFilePath: String, boxType: String, listener: PrepareBoxListener) {
        val videoFile = File(mediaFilePath)
        if (!videoFile.exists()) {
            throw FileNotFoundException("File $mediaFilePath not exists")
        }
        if (!videoFile.canWrite()) {
            throw IllegalStateException("No write permissions to file $mediaFilePath")
        }
        val isoFile = IsoFile(mediaFilePath)
        val moov = isoFile.getBoxes<MovieBox>(MovieBox::class.java)[0]
        var freeBox = findFreeBox(moov)
        val correctOffset = needsOffsetCorrection(isoFile)
        val sizeBefore = moov.size
        var offset: Long = 0
        for (box in isoFile.boxes) {
            if ("moov" == box.type) {
                break
            }
            offset += box.size
        }
        // Create structure or just navigate to Apple List Box.
        var userDataBox: UserDataBox? = Path.getPath(moov, "udta")
        if (userDataBox == null) {
            userDataBox = UserDataBox()
            moov.addBox(userDataBox)
        }
        var metaBox: MetaBox? = Path.getPath(userDataBox, "meta")
        if (metaBox == null) {
            metaBox = MetaBox()
            val hdlr = HandlerBox()
            hdlr.handlerType = "mdir"
            metaBox.addBox(hdlr)
            userDataBox.addBox(metaBox)
        }
        var ilst: AppleItemListBox? = Path.getPath(metaBox, "ilst")
        if (ilst == null) {
            ilst = AppleItemListBox()
            metaBox.addBox(ilst)
        }
        if (freeBox == null) {
            freeBox = FreeBox(128 * 1024)
            metaBox.addBox(freeBox)
        }
        // Got Apple List Box
        var nam: Box? = Path.getPath(ilst, boxType)
        nam = listener.prepareBox(nam)
        ilst.addBox(nam)
        var sizeAfter = moov.size
        var diff = sizeAfter - sizeBefore
        // This is the difference of before/after
        // can we compensate by resizing a Free Box we have found?
        if (freeBox.data.limit() > diff) {
            // either shrink or grow!
            freeBox.data = ByteBuffer.allocate((freeBox.data.limit() - diff).toInt())
            sizeAfter = moov.size
            diff = sizeAfter - sizeBefore
        }
        if (correctOffset && diff != 0L) {
            correctChunkOffsets(moov, diff)
        }
        val baos = BetterByteArrayOutputStream()
        moov.getBox(Channels.newChannel(baos))
        isoFile.close()
        val fc: FileChannel = if (diff != 0L) {
            // this is not good: We have to insert bytes in the middle of the file
            // and this costs time as it requires re-writing most of the file's data
            splitFileAndInsert(videoFile, offset, sizeAfter - sizeBefore)
        } else {
            // simple overwrite of something with the file
            RandomAccessFile(videoFile, "rw").channel
        }
        fc.position(offset)
        fc.write(ByteBuffer.wrap(baos.buffer, 0, baos.size()))
        fc.close()
    }

    @WorkerThread
    @Throws(IOException::class)
    fun splitFileAndInsert(f: File, pos: Long, length: Long): FileChannel {
        val read = RandomAccessFile(f, "r").channel
        val tmp = File.createTempFile("ChangeMetaData", "splitFileAndInsert")
        val tmpWrite = RandomAccessFile(tmp, "rw").channel
        read.position(pos)
        tmpWrite.transferFrom(read, 0, read.size() - pos)
        read.close()
        val write = RandomAccessFile(f, "rw").channel
        write.position(pos + length)
        tmpWrite.position(0)
        var transferred: Long = 0
        while (true) {
            transferred += tmpWrite.transferTo(0, tmpWrite.size() - transferred, write)
            if (transferred == tmpWrite.size())
                break
            //System.out.println(transferred);
        }
        //System.out.println(transferred);
        tmpWrite.close()
        tmp.delete()
        return write
    }

    @WorkerThread
    private fun needsOffsetCorrection(isoFile: IsoFile): Boolean {
        if (Path.getPath<Box>(isoFile, "moov[0]/mvex[0]") != null) {
            // Fragmented files don't need a correction
            return false
        } else {
            // no correction needed if mdat is before moov as insert into moov want change the offsets of mdat
            for (box in isoFile.boxes) {
                if ("moov" == box.type) {
                    return true
                }
                if ("mdat" == box.type) {
                    return false
                }
            }
            throw RuntimeException("I need moov or mdat. Otherwise all this doesn't make sense")
        }
    }

    @WorkerThread
    private fun findFreeBox(c: Container): FreeBox? {
        for (box in c.boxes) {
            //            System.err.println(box.type)
            if (box is FreeBox)
                return box
            if (box is Container) {
                val freeBox = findFreeBox(box as Container)
                if (freeBox != null) {
                    return freeBox
                }
            }
        }
        return null
    }

    @WorkerThread
    private fun correctChunkOffsets(movieBox: MovieBox, correction: Long) {
        var chunkOffsetBoxes = Path.getPaths<ChunkOffsetBox>(movieBox as Box, "trak/mdia[0]/minf[0]/stbl[0]/stco[0]")
        if (chunkOffsetBoxes.isEmpty())
            chunkOffsetBoxes = Path.getPaths(movieBox as Box, "trak/mdia[0]/minf[0]/stbl[0]/st64[0]")
        for (chunkOffsetBox in chunkOffsetBoxes) {
            val cOffsets = chunkOffsetBox.chunkOffsets
            for (i in cOffsets.indices)
                cOffsets[i] += correction
        }
    }

    private class BetterByteArrayOutputStream : ByteArrayOutputStream() {
        val buffer: ByteArray
            get() = buf
    }

}

编写和阅读标题的示例用法:

object MediaMetaData {
    @JvmStatic
    @Throws(IOException::class)
    fun writeTitle(mediaFilePath: String, title: String) {
        MediaMetaDataUtil.writeMetadata(mediaFilePath, AppleNameBox.TYPE, object : MediaMetaDataUtil.PrepareBoxListener {
            override fun prepareBox(existingBox: Box?): Box {
                var nam: AppleNameBox? = existingBox as AppleNameBox?
                if (nam == null)
                    nam = AppleNameBox()
                nam.dataCountry = 0
                nam.dataLanguage = 0
                nam.value = title
                return nam
            }
        })
    }

    @JvmStatic
    fun readTitle(mediaFilePath: String): String? {
        return MediaMetaDataUtil.readMetadata<AppleNameBox>(mediaFilePath, AppleNameBox.TYPE)?.value
    }
}

Answer 1

似乎没有办法对 Android 中所有支持的音频格式统一执行此操作。不过，特定格式的选项有限，因此我建议坚持使用一种格式。

MP3是最受欢迎的，应该有很多选项，比如this one。 .

如果不想处理编码/解码，还有some options for a WAV format .

还有一种方法可以将元数据轨道添加到 MP4 容器中 using MediaMuxer (您可以拥有纯音频 MP4 文件)或 like this .

关于 MediaStore:here's an example (在第 318 页末尾)关于如何在使用 MediaRecorder 后向其添加元数据。尽管据我所知，数据不会记录在文件中。

更新

我编译了an example app使用 this MP4 parser library和 MediaRecorder example from SDK docs .它录制音频，将其放入 MP4 容器并添加如下字符串元数据:

MetaDataInsert cmd = new MetaDataInsert();
cmd.writeRandomMetadata(fileName, "lore ipsum tralalala");

然后在下次应用启动时读取并显示此元数据:

MetaDataRead cmd = new MetaDataRead();
String text = cmd.read(fileName);
tv.setText(text);

更新#2

关于 m4a 文件扩展名:m4a is just an alias for an mp4 file with AAC audio and has the same file format .因此，您可以使用我上面的示例应用程序，只需将文件名从 audiorecordtest.mp4 更改为 audiorecordtest.m4a 并将音频编码器从 MediaRecorder.AudioEncoder.AMR_NB 到 MediaRecorder.AudioEncoder.AAC。