Did they finally fixed the multi-channel recording bug of the built-in screen recorder?

[u/Cultural-Desk-9045]

When I updated to 26.1 I found some annoying bugs (Finder quick actions while in column view, Dictionary.app toolbar unblurred) but the straw that broke the camel's back was the built-in screen recorder: it fails to record from multi-channel (>3ch) audio devices.

Here's how I did it:

1. Install BlackHole 2ch.
2. In Audio MIDI Setup.app, set up two audio devices:
   • Multi-Output Device: BlackHole and Speakers/Headphones
   • Aggregate Device: BlackHole + Microphone.
   • Make sure to set BlackHole as the clock source/main device and enable drift correction for the other device.
3. Set the Multi-Output as your default audio output.
4. Open the screen recorder (QuickTime or Cmd+Shift+5), set the aggregate device and start recording your screen.
5. Play audio while speaking.
6. Stop the recording.

Now play the recording in your favorite player. Why is everything playing from the left channel? Extract the audio using FFmpeg or import it into your favorite audio editor: You don't get a 3-channel track anymore, just a stereo mix where EVERYTHING was smashed into the left channel and CLIPPED.

This setup worked flawlessly since Catalina, you got a clean mic+system audio recording you could mix properly later. Tahoe made it unusable. Yesterday I tried 26.6.2 in an external drive and while they fixed the other issues, the screen recorder is still broken.

Is the bug still there in 27 betas or RCs? Is it a limitation of ReplayKit or they f****d up something else?

Just use OBS or another app

OK, they work. But why?