When my Mac connects to AirPods, starting recording fails.

[ysnows]

System Env:

MacBook Pro 16-inch, 2021

Chip Apple M1 Max

Memory 32 GB 14.3.1 macOS

Error Message:

throwing -10877

HALB_IOThread：：_Start: there already is a thread HALB_IOThread.cpp:323

[ZachNagengast]

Thanks for reporting, this issue has been noticed by some others as well. @cgfarmer4 any thoughts? We definitely need a way to fix this because it's a pretty common use case.

[cgfarmer4]

Hey @ZachNagengast -- thanks for the tag here. I can reproduce. The issue doesn't seem isolated to Airpods, but for all bluetooth headsets. Or at least the 2 others I tried besides my Airpods.

From poking around the web, I see a lot of issues pointing to AVAudioEngine + Bluetooth problems but nothing sticks out as a way forward unfortunately.

[cgfarmer4]

One idea is that if there is some detection of a bluetooth device (not sure how to query this), we could omit the assign input function. 2 other options are:

1. Remove the feature.
2. Switch to using AVCaptureSession instead of AVAudioEngine.

[Abhinay1997]

@cgfarmer4 I have yet to try with a wired device yet but this might be related avaudioengine-crashes-when-plug-headphones-in-or-out

The thread recommends subscribing to the event AVAudioEngineConfigurationChangeNotification and updating the audio nodes. I think this should also be triggered for the bluetooth device getting connected. Thoughts ?

[cgfarmer4]

Decent idea if you want to flip the microphone while you're recording and a good improvement regardless. However, the App doesn't actually crash, it just causes AVAudioEngine to interpret the input in a way that is not compatible and throws warnings. Ive found it doesn't work right even if you start the app with Airpods sometimes.

[Abhinay1997]

Ah I assumed the issue popped up when the app was already recording. I understand what you mean now. That's weird behaviour 🤔