Mac: transmitted WebRTC voice audio is heavily artifacted when the 'Audio Midi Setup' utility is open

Environment

Second Life Release 7.2.2.18475198968 (64bit)
Release Notes

You are at 124.6, 126.9, 30.7 in WebRTC Voice 1 located at simhost-0afd3b4358f8196b2.agni
SLURL: http://maps.secondlife.com/secondlife/WebRTC%20Voice%201/125/127/31
(global coordinates 330365.0, 305791.0, 30.7)
Second Life Preflight 2025-10-29.18924347600
Release Notes

CPU: Apple M1 Pro (2400 MHz)
Memory: 16384 MB
OS Version: macOS 26.0.1 Darwin 25.0.0 Darwin Kernel Version 25.0.0: Wed Sep 17 21:41:45 PDT 2025; root:xnu-12377.1.9~141/RELEASE_ARM64_T6000 arm64
Graphics Card Vendor: Apple
Graphics Card: Apple M1 Pro

OpenGL Version: 4.1 Metal - 90.5

Window size: 938x704
Font Size Adjustment: 96pt
UI Scaling: 0.75
Draw distance: 88m
Bandwidth: 10000kbit/s
LOD factor: 1.125
Render quality: 1
Texture memory: 12124MB
Disk cache: Max size 2150.4 MB (84.0% used)
HiDPI display mode:

J2C Decoder Version: KDU v8.4.1
Audio Driver Version: OpenAL, version 1.1 ALSOFT 1.24.2 / OpenAL Community / OpenAL Soft: OpenAL Soft
Dullahan: 1.24.0.202510081737
CEF: 139.0.40+g465474a+chromium-139.0.7258.139
Chromium: 139.0.7258.139
LibVLC Version: 3.0.21
Voice Server Version: Secondlife WebRTC Gateway

Packets Lost: 0/315 (0.0%)
November 07 2025 09:59:37

Description

If a user on Mac OS speaks in WebRTC voice while the built-in 'Audio Midi Setup.app' utility is open, their audio is heavily heavily artifacted (very choppy, and slightly "robotic" sounding) to other nearby users. This appears to be a Mac OS audio system bug, rather than something that could be addressed in the SL viewer.

This issue does not appear to reproduce (at least not to the same extent) when the user visits a region that uses Vivox 4.10.0000.32327.5fc3fe7c.5942f08.

Reproduction steps

1. UserA (on Mac) and UserB (on a separate machine - any platform): visit the same location which uses webRTC for voice chat
2. UserA: speak in nearby chat
3. UserB: note the quality of UserA's voice stream
4. UserA: In Finder, open Applications -> Utilities -> "Audio Midi Setup.app"
5. UserA: speak more in nearby chat
6. UserB: note the quality of UserA's voice stream
7. UserA: close "Audio Midi Setup.app"
8. UserA: speak more in nearby chat
9. UserB: note the quality of UserA's voice stream

Expected results:
UserB should hear UserA clearly whether UserA has "Audio Midi Setup.app" open or not.

Actual results:
UserB hears UserA clearly before they open "Audio Midi Setup.app" and after the application is closed, but UserA's voice is very choppy and slightly robotic-sounding while they have the application open.

No source file, test, or entry point is identified in the report. Start by confirming whether the viewer's macOS WebRTC audio path is involved and whether the artifacting can be reproduced with Audio Midi Setup open; done would require a confirmed viewer-side scope and a reproducible test or a documented conclusion that no viewer change is possible.