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LlamaCasty/TASKS/task-08-audio-milestone.md
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gramps 87509bcf99 docs: restructure TASKS.md into a catalog — one file per task in TASKS/
TASKS.md is now the index (status table, open items, research pointer).
33 files: 32 task files + 1 research facts file. The full take-saga
narrative and all design decisions are preserved verbatim; the catalog
makes the queue readable without opening every task body. Schema and
AGENTS.md updated to reflect the new layout.
2026-09-05 16:31:46 -07:00

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# TASK 8 — Audio milestone: real stream audio + voice filters + TRAX music (2026-08-14)
> Catalog: [`TASKS.md`](../TASKS.md) — status and requirements live here.
**Goal:** every audio issue done and tested in one branch — real mic/game audio reaches the encoder (replacing the `anullsrc` silence), `MicVolume`/`GameAudioVolume`/mute become real pre-AAC gains, TASK 10's voice filters land, auto-duck keeps the creator's voice over game + music, and a free background-music source ("TRAX") plays into the sound bar and the stream.
### Status: ✅ SHIPPED 2026-08-14 — 196 tests passing, 0 warnings (ONE integration test: `AudioPipelineTests.Mix_WithFiltersDuckAndGain_Lands_On_AudioPipe`)
1. ✅ **Real audio into the encoder** — the mixer's loopback samples were **dropped today** (`AudioMixer.OnLoopbackSample` metered only) and `MicVolume` was meter-only; `FfmpegArgs.cs:28` ran `-f lavfi -i anullsrc` (silence). Transport: **ffmpeg reads a Windows named pipe** — `-f f32le -ar 48000 -ac 2 -i \\.\pipe\ytllive_audio` replaces the anullsrc block, plus explicit `-map 0:v -map 1:a`; pipe name via `EncoderOptions.AudioPipeName` (`DefaultAudioPipeName = "ytllive_audio"`). Mixer stays **two inputs (mic + loopback)** — no N-source abstraction, no `StereoMixer` class. The VM owns the pipe lifecycle (`BeginGoLive` → `_audioMixer.StartLive(pipeName)`, `StopStream` → `_audioMixer.StopLive()` before the pump stops); `FfmpegEncoder.cs` is untouched.
2. ✅ **Honest gains reach the stream** — `MicVolume` scales the mic channel; `GameAudioVolume` + mute scale the loopback channel (the "mute in preview but stream still plays" footgun dies with it). One knob per input = KISS. Implemented as `Func<double>` gain seams on `AudioMixer` (`micGain`/`loopbackGain`), wired by `MainViewModel`.
3. ✅ **Voice filters (TASK 10, before the meter AND the mix)** — `VoiceFilterChain`: bass (`LowShelfFilter` 120 Hz +4 dB) → treble (`HighShelfFilter` 8 kHz +3 dB) → **noise gate** (pure C#, creator's choice) → compressor (threshold 0.5, 4:1). Pure stateful DSP (TDF2), sine-in unit tests. Meter stays post-filter.
4. ✅ **Auto-duck** — pure envelope (`AutoDucker`): mic RMS > 0.02 → game+music dip ×0.25 (~12 dB), attack 0.05 / release 0.005, recover on release. Always-on, no knobs. Strong form of the creator's "voice always over the game volume" idea.
5. ✅ **TRAX — background music, FREE** (keeps the one paid line = Alerts + flash removal). `MusicPlayer`: NAudio `MediaFoundationReader` (mp3/wav/m4a) → `VolumeWaveProvider16` at the hardcoded **0.20** (fixed, not changeable) → `WaveOutEvent` on the default device (added the sibling `NAudio.WinMM` 2.2.1 package — `WaveOutEvent` isn't in `NAudio.Wasapi`), loop on end. **No 3rd mixer input and no `MusicVolume`** — music plays on the desktop, the existing loopback picks it up: heard in headphones, the sound-bar meter bounces, and the stream carries it through the loopback channel (ducked with game when the voice is hot). Known wrinkle (out of scope): YouTube mutes VODs carrying copyrighted music — future "music on live, off VOD".
6. ✅ **TRAX footer control (final spec, agreed 2026-08-14)** — `YtButtonSecondary`, **status dot + "TRAX"** text, in the center footer stack beside MIC:
- **Status dot** (same 8px Ellipse pattern as MIC/Socials): **red** no track loaded · **yellow** loaded not playing · **green** playing.
- **Left-click** → toggle play/pause; no track loaded → opens the picker instead.
- **Right-click** → always opens the in-app track picker (`TraxButton_PreviewMouseRightButtonUp`, code-behind pattern like `GameSpeaker_MouseLeftButtonUp`, `e.Handled = true` so no context menu).
- **Tooltip** → playing/loaded track name; "No track — right-click to choose background music" when empty.
- **No slider** — volume is the 0.20 constant. Picker = plain OS `OpenFileDialog` filtered to mp3/wav/m4a/aac/flac/ogg.
7. ✅ **Sound bar shows music** — `IsGameAudioBarVisible = gameDetectorProducingSound || isMusicPlaying`; relabelled "Game Audio Capture" → **"Desktop Audio"** (TRAX rides the same channel). **Follow-up (2026-08-15): the gating is gone — the game audio bar is ALWAYS visible** (the `IGameAudioDetector`/`GameAudioDetector`/`GameAudioHysteresis` stack + the VM's 250ms poll timer and their tests were deleted; the bar kept hiding the desktop meter when no full-screen game with sound was up, and the creator wants it pinned).
8. ✅ **Capture hardening (design changed at build time)** — the plan's "force IEEE-float 48 kHz on both WASAPI sources" was **dropped**: NAudio 2.2.1's `WasapiCapture` exposes no overridable `GetDefaultMixFormat`, so both sources capture the device's own mix format and the mixer's pure `TinyResampler` normalizes any rate/channel count to 48 kHz stereo (the resampler IS the design, not a fallback). Stop path disposes the audio pipe (EOF) in `MainViewModel.StopStream` before the pump stops, so both ffmpeg inputs end in order.
9. ✅ **Schema v9** — single-row `Music` (`TrackPath`, `IsEnabled`; volume is the 0.20 constant) + migration in `LayoutStore.cs` (`user_version` 9; `Save` gained an optional `Music? music = null` param so existing 3-arg callers still compile; load query + null reset).
10. ✅ **Docs in the same commit** — `ai.md` audio section rewritten ("one knob per input", 2-in mix, auto-duck, TRAX free, VOD-mute wrinkle), TASK 10's status, this task's status, HANDOFF.
**Files (new):** `Services/Audio/VoiceFilterChain.cs` (+ `LowShelfFilter`/`HighShelfFilter`/`NoiseGate`/`Compressor`), `Services/Audio/AudioRingBuffer.cs` (async-arrival source buffers), `Services/Audio/AutoDucker.cs`, `Services/Audio/TinyResampler.cs`, `Services/Audio/MusicPlayer.cs`, `Services/Audio/NamedPipeAudioWriter.cs` (+ `IAudioPipeWriter` seam), `Models/Music.cs`.
**Files (changed):** `AudioMixer.cs` (filter chain before meter+mix, loopback into the mix, gains via `Func<double>` seams, ducker, silence-filler so the pipe never stalls, `StartLive`/`StopLive`), `WasapiMicAudioSource.cs` (device mix format — resampler normalizes; no forced format), `FfmpegArgs.cs` (named-pipe input + `-map`, name via `EncoderOptions.AudioPipeName`), `EncoderOptions.cs` (`AudioPipeName`), `ytLive.csproj` (`NAudio.WinMM` 2.2.1 for `WaveOutEvent`), `LayoutStore.cs` (schema v9), `MainViewModel.cs`/`MainWindow.xaml`/`MainWindow.xaml.cs` (footer TRAX group, sound-bar visibility OR music, go-live starts the pipe, end closes it first).
**Testing (Good Dog Rule — ONE integration test):** `AudioPipelineTests.Mix_WithFiltersDuckAndGain_Lands_On_AudioPipe` — real filter chain + mixer + ducker + `NamedPipeAudioWriter`, fake `IAudioSource`s, test-side `NamedPipeClientStream` reads the bytes and asserts post-filter/post-gain/post-duck mixed stereo (ring buffers pre-filled so the first pipe tick already carries real audio — avoids a start-of-stream silence race). Units: each DSP stage (known sine-in → expected gain), ring buffer wrap/underflow/overwrite, ducker envelope, resampler (down/up/stateful/identity), `FfmpegArgs` pipe+map, schema v9 roundtrip + no-music-row. Existing tests stay green.
**Out of scope (this branch):** IP webcam (video-only when it lands — never an audio input), chat box source (TASK 3 item 18), alt-key crop, credits, background removal, music-off-VOD, `PremiumUrl` (TASK 10 seam).