[iOS] No Audio Input When Streaming Through Headphones

[Goolpe]

Package version
^5.2.0

Environment

• OS: iOS
• Tested on airpods 3 and pro 2, iPhone 11

Describe the bug

When recording audio through headphones, no sound is produced. Instead, the following data is received:
[0, 8, 254, 232, 68, 0, 0, 0, 0, 0, 0, 0, ... zeros ..., 0].

To Reproduce

Steps to reproduce the behavior:

1. Copy and paste the code
2. Run the app on iOS
3. Connect headphones (airpods)
4. Press start and try to say something
5. Press stop
6. Disconnect headphones and try again

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

void main() {
  runApp(_App());
}

class _App extends StatelessWidget {
  const _App({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: _TestRecorder(),
    );
  }
}

class _TestRecorder extends StatefulWidget {
  const _TestRecorder({super.key});

  @override
  State<_TestRecorder> createState() => _TestRecorderState();
}

class _TestRecorderState extends State<_TestRecorder> {
  final _recorder = AudioRecorder();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(
              onPressed: () async {
                final stream = await _recorder
                    .startStream(const RecordConfig(encoder: AudioEncoder.pcm16bits));

                stream.listen((data) {
                  print('DATA: ${data.buffer.asUint8List()}');
                });
              },
              child: const Text('START'),
            ),
            ElevatedButton(
              onPressed: () async {
                await _recorder.stop();
              },
              child: const Text('STOP'),
            ),
          ],
        ),
      ),
    );
  }
}

Expected behavior

Audio should be recorded through the connected headphones.

[llfbandit]

Thanks for reporting.
This issue is unclear to me. Do you mean that the first try works and not the subsequent tries?

[Goolpe]

No, it never works...
It always returns the same list [0, 8, 254, 232, 68, 0, 0, 0, 0, 0, 0, 0, ... zeros ..., 0]

[llfbandit]

Does it work with file recording?

[Goolpe]

Hm, interesting, it works now with startStream,
But it's strange, some users sent us feedback that airpods didn't work in our app on ios
I tested and it worked at that moment, but after some days,
I tried it again in app and with this example (in issue) without any other packages, and it didn't work.
But now it works...
Could some other apps / configurations affect?

[llfbandit]

Could some other apps / configurations affect?

It may internally in your app. IosRecordConfig.manageAudioSession could help in this area.

Is this issue resolved?

[Goolpe]

Didn't resolve yet... We disabled manageAudioSession in our project, but our users still have this problem.
We reproduced it only twice, but not sure what could have caused the issue.
We use unity and video player (they reconfigure audio session). And we should change the audio session configuration every time to use record package properly, but sometimes something goes wrong and the headphones on iOS don't work...