stream recording data only half

[ineyee]

Package version
6.0.0

Environment

• OS: [iOS 18.5]
• I am using a wireless microphone for audio recording, which supports the following specifications:
  ​Sampling Rate: 48 kHz
  ​Channel Count: 2 (stereo)
  ​Bit Depth: 16-bit

Describe the bug

code

Future<Stream<Uint8List>?> startRecorderStream(
    {required InputDevice device}) async {
  if (await _record!.hasPermission()) {
    _startTimer();

    _audioStream = await _record!.startStream(RecordConfig(
      encoder: AudioEncoder.pcm16bits,
      sampleRate: 48000,
      numChannels: 1,
      device: device,
    ));

    return _audioStream!;
  } else {
    return null;
  }
}

_recordingSubscription = audioStream.listen((data) async {
  debugPrint("===>Frame size: ${data.length}, total received: $totalBytes");

  final bufferToSend = Uint8List.fromList(data);

  await _writePcmDataToFile(data: bufferToSend);
});

log

flutter(17.50.18.4752): ===>Frame size: 4800, total received: 4800
flutter(17.50.18.5528): ===>Frame size: 4800, total received: 9600
flutter(17.50.18.6681): ===>Frame size: 4800, total received: 14400
flutter(17.50.18.7620): ===>Frame size: 4800, total received: 19200
flutter(17.50.18.8579): ===>Frame size: 4800, total received: 24000
flutter(17.50.18.9812): ===>Frame size: 4800, total received: 28800
flutter(17.50.19.0728): ===>Frame size: 4800, total received: 33600
flutter(17.50.19.1553): ===>Frame size: 4800, total received: 38400
flutter(17.50.19.2794): ===>Frame size: 4800, total received: 43200
flutter(17.50.19.3707): ===>Frame size: 4800, total received: 48000
...

Under the parameters of 48kHz sampling rate, 1 channel, and 16-bit depth, the theoretical data throughput should be calculated as follows:
48,000 samples/second × 1 channel × 2 bytes/sample = 96,000 bytes/second.

Consequently, within a 100ms interval, the expected data payload should be:
96,000 bytes/second × 0.1 seconds = 9,600 bytes.

However, during actual operation, the audioStream.listen callback (triggered approximately every 100ms) consistently returns only ​4,800 bytes​ of data per event. This represents a ​50% deficit​ compared to the theoretical payload requirement.

Expected behavior

I am directly storing the acquired data in real-time into a .pcm file. When playing this file using ffplay with the parameters -ar 48000 -ac 1 -f s16le, the audio exhibits ​2x accelerated playback​ (double-speed effect). This indicates a critical mismatch between the ​expected data throughput​ and ​actual signal acquisition.

[ineyee]

i have solved