[itsmeyaw]

Summary

Two separate bugs together made some apps impossible to control: FineTune muted their original output and played back silence. Discord shows both bugs at once.

1. Nested helper apps showed up as their own app row

Chromium and Electron apps often play audio from a helper bundle inside the main app, for example Discord.app/Contents/Frameworks/Discord Helper (Renderer).app. NSWorkspace lists these helpers as running .app bundles, so FineTune treated them as top-level apps. The audio appeared under a separate "Discord Helper (Renderer)" row instead of "Discord".

 resolve app for audio process
   responsible PID → running app
-  accept if bundleURL ends in .app
+  accept if bundleURL ends in .app AND is not nested inside another .app
   else walk up the process tree (same check)

The new AudioProcessMonitor.isTopLevelAppBundle(_:) check is used in both lookups.

2. The input peak scan read only the first channel

The audio callback measures the peak of the tapped input. That peak drives the VU meter and the output gate, which stays closed until it detects sound. The scan stepped through interleaved samples by the channel count, so it read only channel 0. An app that renders into only one side of a stereo stream reads as silence, so the gate never opens. Because the tap is .mutedWhenTapped, the app's original output is muted too, and the user hears nothing.

 inputPeak(buffers)
   for each buffer
-    for i in stride(0, sampleCount, by: channels)   // channel 0 only
+    for i in 0..<sampleCount                        // every channel
       peak = max(peak, |sample[i]|)
   return min(peak, 1), frames

The scan moved into ProcessTapController.inputPeak(_:) (static, @inline(__always)) so it can be tested. It stays RT-safe: no allocations, locks or logging.

Evidence

Example case: Discord on macOS 27.0.1, playing sound to the built-in speakers.

• Before: Discord appeared as "Discord Helper (Renderer)". After merging the rows, the Discord meter stayed flat, the slider had no effect, and Discord went silent while FineTune ran. Discord was audible again as soon as FineTune quit.
  A separate raw tap on the same process showed real audio on the right channel only:
  L=0.000000 R=0.542171 ch=2, while FineTune's own level for Discord stayed at 0.000000.
• After: there is a single "Discord" row. Discord is audible, the meter moves, and the slider changes the volume (verified on hardware).

Regression tests (Swift Testing):

AudioProcessMonitorBundleTests
  topLevelAppIsReal            /Applications/Discord.app                         → true
  nestedHelperAppIsNotReal     …/Discord.app/Contents/Frameworks/…Helper….app    → false
  xpcServiceAndNilAreNotReal   *.xpc, nil                                        → false

InputPeakTests
  rightOnlyStereo   L=0, R=0.5 interleaved   → peak 0.5 (was 0.0), frames 256
  clamped           -3.0                     → peak 1.0

The full unit test suite passes (-skip-testing:FineTuneUITests).

[sheeesh3]

hey, tried this locally on macos 27.0.1 and it fixed the issue for me.

some clips with audio only on the right channel were silent at my usual volume. turning it up made them audible but it kept cutting in and out.

same clips play fine now at the volume where they had no sound before.

been dealing with this daily so thanks for the fix! would be nice to see this merged.