Save audio stream / Uint8List data in file flutter

Question

I am getting Uint8List from recorder plugin for Android and iOS both. I want to write the data in a local playable audio file whenever I am getting the data in my stream subscription of a mic. Is there any possible way to write the data?

Currently, I am storing the data like

recordedFile.writeAsBytesSync(recordedData, flush: true);

It's writing data to file but not able to play from the file storage. But also if I read the same file and gives it's bytes to plugin it's playing the same buffer.

Answer 1

I have added a WAVE/RIFF Header before writing my bytes into the file which gives the metadata to bytes and file.

I have 16 BIT PCM audio bytes with MONO channel in my stream. I am appending those bytes in a list of bytes when I am receiving the bytes.

List<int> recordedData = [];
recordedData.addAll(value);

Now I have all the recorded bytes on my list. After stopping my recorder I called the below function. Which takes all the data and sample rate for recorded. in my case its 44100.

await save(recordedData, 44100);

Future<void> save(List<int> data, int sampleRate) async {
    File recordedFile = File("/storage/emulated/0/recordedFile.wav");

    var channels = 1;

    int byteRate = ((16 * sampleRate * channels) / 8).round();

    var size = data.length;

    var fileSize = size + 36;

    Uint8List header = Uint8List.fromList([
      // "RIFF"
      82, 73, 70, 70,
      fileSize & 0xff,
      (fileSize >> 8) & 0xff,
      (fileSize >> 16) & 0xff,
      (fileSize >> 24) & 0xff,
      // WAVE
      87, 65, 86, 69,
      // fmt
      102, 109, 116, 32,
      // fmt chunk size 16
      16, 0, 0, 0,
      // Type of format
      1, 0,
      // One channel
      channels, 0,
      // Sample rate
      sampleRate & 0xff,
      (sampleRate >> 8) & 0xff,
      (sampleRate >> 16) & 0xff,
      (sampleRate >> 24) & 0xff,
      // Byte rate
      byteRate & 0xff,
      (byteRate >> 8) & 0xff,
      (byteRate >> 16) & 0xff,
      (byteRate >> 24) & 0xff,
      // Uhm
      ((16 * channels) / 8).round(), 0,
      // bitsize
      16, 0,
      // "data"
      100, 97, 116, 97,
      size & 0xff,
      (size >> 8) & 0xff,
      (size >> 16) & 0xff,
      (size >> 24) & 0xff,
      ...data
    ]);
    return recordedFile.writeAsBytesSync(header, flush: true);
  }

And it's creating the playable WAV file.