TASK 25: master limiter on the live mix (2026-08-15, queued from the TRAX discussion) — the review confirmed two of the creator's three instincts were already satisfied (MediaFoundationReader streams from disk so file size needs no guard; the MusicPlayer 0.20 bed rides the same loopback gain as the game, so music is always exactly 20% of the desktop volume by construction) and found one real gap: AudioMixer.FillAndMix summed mic + loopback with no output ceiling, so hot gains could pass 0 dBFS and clip the AAC encode. New pure Services/Audio/MasterLimiter.cs: -1 dBFS ceiling (Ceiling = 0.891), instant attack per frame (a hot frame is scaled exactly to the ceiling — no overshoot), smoothed release toward unity so loud passages don't pump, gain never exceeds 1. Applied at the end of FillAndMix right before the pipe write. 3 unit tests (trim-to-ceiling, never-boost, recovery) + ONE integration test (MasterLimiter_CapsTheLiveMix_OnThePipe: a 0.95 loopback bed capped to exactly 0.891 on the wire while staying audible). Docs in the same commit: ai.md go-live audio section, Services/index.md new row, TASKS.md TASK 25 record, HANDOFF.md shipped state. Build 0 warnings, 193 tests passing (189 + 4 new)

2026-08-15 16:10:16 -07:00
parent 24f16b2cd9
commit 92f1471ab4
7 changed files with 201 additions and 9 deletions
@@ -51,6 +51,7 @@ External-facing logic: YouTube API, persistence. See
 | `Audio/AudioMixer.cs` | Owns both sources; capture starts once at startup (`MainViewModel.StartMicCaptureAsync`) and stops on `Shutdown` — NOT go-live (preview monitoring). Mic samples → `AudioLevelMeter` → `MicLevelChanged`; loopback samples → the game bar's meter via `LoopbackLevelChanged`. Surfaces mic connection state: `MicConnected`/`MicFailed` (drives the status dot) + `RestartMic()` (device swap mid-session, keeps loopback). Failures log via `AppLog`; mic failure zeroes the meter, loopback failure doesn't kill the mic. Note: the meter `Push` is unconditional (the `?.` on the event would otherwise skip the argument when nothing is subscribed) |
 | `Audio/AudioLevelMeter.cs` | Pure smoothed RMS level (0..1): `Push(AudioSample)` + `Reset` — the unit-tested math behind `AudioLevel` and `GameAudioLevel`. `ToDisplay(float)` maps the raw linear RMS onto the meter's display scale (−60..0 dBFS spread across 0..1, with **+10 dB input amplification** so real speech peaks hit the red zone at maxed volume) — real speech/game RMS (~0.01..0.1) would otherwise leave a flat scale looking dead; ≤0.001 linear reads as zero (never idles on background noise) |
 | `Audio/WaveToFloat.cs` | Pure WASAPI buffer → float conversion: IEEE float 32-bit direct, PCM 16-bit normalized, `WaveFormatExtensible` IEEE-float subformat GUID, trailing partial samples ignored |
+| `Audio/MasterLimiter.cs` | **Master output limiter**: a **−1 dBFS ceiling** (`Ceiling = 0.891`) applied after the live mix so the honest gains can never sum past 0 dBFS and clip the AAC encode. Instant attack per frame (a hot frame is scaled exactly to the ceiling — no overshoot), smoothed release toward unity so loud passages don't pump. Pure — unit-tested |

 Related: constructed in [`ViewModels/MainViewModel.cs`](../ViewModels/MainViewModel.cs)
 (no DI container yet). Models in [`Models/index.md`](../Models/index.md).