All zero bytes when streaming in pcm16 on MacOS

[ardera]

Environment

• macOS 15

Describe the bug
When using AudioRecorder.startStream(RecordConfig(encoder: AudioEncoder.pcm16bits)) on macOS, the recorded audio chunks are all zero.

To Reproduce

1. Create a blank flutter create app
2. upgrade the minimum macos deployment to 10.15
3. use this as the main.dart

import 'dart:async';
import 'dart:io';

import 'package:flutter/material.dart';
import 'package:record/record.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  
  final recorder = AudioRecorder();
  final chunkStream = await recorder.startStream(
    RecordConfig(encoder: AudioEncoder.pcm16bits),
  );

  final chunksFuture = chunkStream.toList();

  await Future.delayed(Duration(seconds: 5));

  await recorder.stop();
  await recorder.dispose();

  final chunks = await chunksFuture;

  chunks.any((chunk) => chunk.any((byte) => byte != 0))
      ? print('Audio data detected')
      : print('No audio data detected');

  exit(0);
}

Expected behavior
Expected would be that there are at least some non-zero bytes.

[llfbandit]

Thanks for reporting.
I didn't reproduced the issue on my side. But I re-used my example project with your reproducer.

What about the permission request?

await recorder.hasPermission()

<key>NSMicrophoneUsageDescription</key>
<string>Some message to describe why you need this permission</string>

[ardera]

Okay so with the com.apple.security.device.audio-input entitlement it works (the NSMicrophoneUsageDescription by itself didn't work), but recorder.hasPermission() is true in either case, with or without the entitlement or NSMicrophoneUsageDescription.
Was just a bit confusing, because I also got the permission request for microphone access from MacOS when launching the app, so it seemed like the macOS side was fine. 🤷

[llfbandit]

Yeah, NSMicrophoneUsageDescription is the requested permission.
com.apple.security.device.audio-input is the capability. I don't know if there's any possiblity to check this also on this platform.

[ardera]

fyi, just in case anyone else stumbled upon this issue, it seems like the original issue I had (in my real app, not the reproduction app) was not due to permissions, but apparently some tab in firefox was also using the microphone, even though I paused recording there and firefox was minimized. Had to close the tab and additionally restart the app, only then did it work again.