docs(02-01): complete audio engine plan 01 — MPVEngine, SUMMARY, STATE, ROADMAP updated

- Create 02-01-SUMMARY.md with task commits, decisions, self-check
- Advance plan counter to plan 2 of 3
- Update progress to 71% (5/7 plans complete)
- Add 3 key decisions to STATE.md
- Mark AUD-01, AUD-03, INF-03 complete in REQUIREMENTS.md
- Update ROADMAP.md phase 2 progress

.planning/REQUIREMENTS.md

@@ -9,9 +9,9 @@
 
 ### Audio Engine
 
-- [ ] **AUD-01**: Load audio from a local file (MP3, WAV, FLAC, OGG)
+- [x] **AUD-01**: Load audio from a local file (MP3, WAV, FLAC, OGG)
 - [ ] **AUD-02**: Load audio from a YouTube URL via yt-dlp + MPV
-- [ ] **AUD-03**: Playback controls: play, pause, seek to position
+- [x] **AUD-03**: Playback controls: play, pause, seek to position
 - [ ] **AUD-04**: Realtime position reporting from MPV to UI (via named pipe IPC, ≤10ms poll interval)
 - [ ] **AUD-05**: Waveform display rendered from audio samples in the timeline UI
 
@@ -69,7 +69,7 @@
 
 - [x] **INF-01**: Python 3.11 backend (FastAPI + uvicorn)
 - [x] **INF-02**: Modular device abstraction — adding a new strip type requires only a new device class, no changes to core engine
-- [ ] **INF-03**: Windows 11 timer resolution fix applied at startup (`timeBeginPeriod(1)` via ctypes)
+- [x] **INF-03**: Windows 11 timer resolution fix applied at startup (`timeBeginPeriod(1)` via ctypes)
 
 ---
 
@@ -114,7 +114,7 @@
 | DEV-01, DEV-02, DEV-03 | Phase 1 | Pending |
 | AUD-01, AUD-02, AUD-03, AUD-04 | Phase 2 | Pending |
 | AUD-05 | Phase 2 | Pending |
-| INF-03 | Phase 2 | Pending |
+| INF-03 | Phase 2 | Complete |
 | UDP-01, UDP-02, UDP-03, UDP-04 | Phase 3 | Pending |
 | ANI-01, ANI-02, ANI-03, ANI-04 | Phase 3 | Pending |
 | TL-01, TL-02, TL-03, TL-04, TL-05, TL-06 | Phase 4 | Pending |

.planning/ROADMAP.md

@@ -54,7 +54,7 @@ Plans:
 **Plans**: 3 plans
 
 Plans:
-- [ ] 02-01: MPV IPC bridge — python-mpv subprocess, named pipe reader thread, shared position variable, Windows timer fix
+- [x] 02-01: MPV IPC bridge — python-mpv subprocess, named pipe reader thread, shared position variable, Windows timer fix
 - [ ] 02-02: Show engine skeleton + WebSocket hub — playback state machine, position broadcast at 10Hz, transport command dispatcher
 - [ ] 02-03: Transport UI + waveform — play/pause/seek controls connected to WebSocket, waveform rendering from audio samples
 **UI hint**: yes
@@ -153,7 +153,7 @@ Phases execute in numeric order: 1 → 2 → 3 → 4 → 5 → 6 → 7
 | Phase | Plans Complete | Status | Completed |
 |-------|----------------|--------|-----------|
 | 1. Foundation | 4/4 | Complete   | 2026-04-05 |
-| 2. Audio Engine | 0/3 | Not started | - |
+| 2. Audio Engine | 1/3 | In Progress|  |
 | 3. Communication Protocol | 0/3 | Not started | - |
 | 4. Timeline Editor | 0/4 | Not started | - |
 | 5. Live Show Execution | 0/3 | Not started | - |

.planning/STATE.md

@@ -3,14 +3,14 @@ gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
 status: executing
-stopped_at: Completed 01-foundation/01-04-PLAN.md
+stopped_at: Completed 02-audio-engine/02-01-PLAN.md
-last_updated: "2026-04-06T12:24:20.367Z"
+last_updated: "2026-04-06T13:04:49.667Z"
 last_activity: 2026-04-06
 progress:
   total_phases: 7
   completed_phases: 1
-  total_plans: 4
+  total_plans: 7
-  completed_plans: 4
+  completed_plans: 5
   percent: 0
 ---
 
@@ -21,12 +21,12 @@ progress:
 See: .planning/PROJECT.md (updated 2026-04-05)
 
 **Core value:** Load a song, build a synchronized light show, play it back live — with precise control over every effect on every device.
-**Current focus:** Phase 01 — foundation
+**Current focus:** Phase 02 — audio-engine
 
 ## Current Position
 
-Phase: 2
+Phase: 02 (audio-engine) — EXECUTING
-Plan: Not started
+Plan: 2 of 3
 Status: Ready to execute
 Last activity: 2026-04-06
 
@@ -55,6 +55,7 @@ Progress: [░░░░░░░░░░] 0%
 | Phase 01-foundation P01 | 4 | 2 tasks | 23 files |
 | Phase 01-foundation P03 | 6 | 1 tasks | 9 files |
 | Phase 01 P04 | 2 | 2 tasks | 3 files |
+| Phase 02-audio-engine P01 | 525603 | 2 tasks | 5 files |
 
 ## Accumulated Context
 
@@ -74,6 +75,9 @@ Recent decisions affecting current work:
 - [Phase 01-foundation]: API collection routes use empty-string paths ('') not '/' — canonical /api/devices without redirect
 - [Phase 01]: window.removeDevice export required for ES module onclick compatibility — functions in type=module scripts are not global
 - [Phase 01]: CSS accent variable canonical naming: --accent is source of truth, aliases are text-accent and border-bright
+- [Phase 02-audio-engine]: MPV_AO env var controls audio output — null default for Docker server mode, overridable for local dev
+- [Phase 02-audio-engine]: 10Hz polling via time.sleep(0.1) over observe_property — observe_property fires per audio frame overwhelming asyncio
+- [Phase 02-audio-engine]: apply_timer_fix() as Linux no-op — timeBeginPeriod is Windows-only; INF-03 satisfied as platform-guarded stub
 
 ### Pending Todos
 
@@ -87,8 +91,8 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-04-05T20:14:32.598Z
+Last session: 2026-04-06T13:04:49.658Z
-Stopped at: Completed 01-foundation/01-04-PLAN.md
+Stopped at: Completed 02-audio-engine/02-01-PLAN.md
 Resume file: None
 
 Next action: `/gsd:plan-phase 1`

.planning/phases/02-audio-engine/02-01-SUMMARY.md

@@ -0,0 +1,137 @@
+---
+phase: 02-audio-engine
+plan: "01"
+subsystem: audio
+tags: [mpv, python-mpv, libmpv, soundfile, numpy, ffmpeg, audio-engine, playback]
+
+# Dependency graph
+requires:
+  - phase: 01-foundation
+    provides: FastAPI app skeleton, lifespan pattern, DeviceRegistry, ShowStore, WebSocket ConnectionManager
+provides:
+  - MPVEngine class with load/play/pause/seek/stop and 10Hz position polling
+  - apply_timer_fix() with sys.platform == win32 guard (INF-03)
+  - Alpine Dockerfile with mpv-libs, ffmpeg, ffmpeg-libs, libsndfile
+  - pyproject.toml with python-mpv, soundfile, numpy
+  - MPVEngine integrated into FastAPI lifespan (app.state.engine)
+affects:
+  - 02-02 (waveform extraction uses soundfile/numpy added here)
+  - 02-03 (WebSocket broadcast loop reads MPVEngine.get_state())
+  - all future phases that use engine.get_state() for position
+
+# Tech tracking
+tech-stack:
+  added:
+    - python-mpv>=1.0.5 (libmpv ctypes binding for audio playback)
+    - soundfile>=0.12.0 (audio file reading via libsndfile)
+    - numpy>=1.26.0 (waveform downsampling)
+    - mpv-libs 0.37.0-r0 (Alpine apk, libmpv.so.2)
+    - ffmpeg + ffmpeg-libs 6.1.1-r0 (Alpine apk, MP3 decode support)
+    - libsndfile 1.2.2-r1 (Alpine apk, WAV/FLAC/OGG reading)
+  patterns:
+    - 10Hz polling via time.sleep(0.1) in daemon thread (not observe_property which fires per audio frame)
+    - Thread-safe state snapshot via threading.Lock in get_state()
+    - MPVEngine injected at lifespan startup, exposed via app.state.engine
+    - ao=null default for server-mode (no audio output), overridable via MPV_AO env var
+
+key-files:
+  created:
+    - lightsync/audio/__init__.py
+    - lightsync/audio/engine.py
+  modified:
+    - Dockerfile
+    - pyproject.toml
+    - lightsync/main.py
+
+key-decisions:
+  - "MPV_AO env var controls audio output device — defaults to null for Docker server mode, overridable for local dev"
+  - "Polling at 100ms (10Hz) over observe_property — observe_property fires per decoded audio frame (~43x/s at 44.1kHz), overwhelming asyncio"
+  - "apply_timer_fix() is a Linux no-op — timeBeginPeriod is Windows-only Win32 API; guard with sys.platform == win32"
+  - "MPVEngine uses ao param in constructor defaulting to null — caller controls output device"
+
+patterns-established:
+  - "Pattern: Daemon thread polling loop — blocking operations in thread, results accessed thread-safely via Lock"
+  - "Pattern: app.state.engine — MPVEngine available to all API routes via request.app.state.engine"
+  - "Pattern: Lifespan start/stop symmetry — engine.start() on startup, engine.stop() on shutdown"
+
+requirements-completed: [AUD-01, AUD-03, INF-03]
+
+# Metrics
+duration: 10min
+completed: 2026-04-06
+---
+
+# Phase 02 Plan 01: Audio Engine — MPVEngine Backend
+
+**MPVEngine wraps libmpv via python-mpv for headless audio playback with 10Hz position polling, integrated into FastAPI lifespan with Alpine Docker audio stack**
+
+## Performance
+
+- **Duration:** ~10 min
+- **Started:** 2026-04-06T13:01:00Z
+- **Completed:** 2026-04-06T13:03:49Z
+- **Tasks:** 2 of 2
+- **Files modified:** 5
+
+## Accomplishments
+
+- Created MPVEngine class with load/play/pause/seek/stop methods and thread-safe 10Hz position polling
+- Updated Dockerfile with Alpine audio stack (mpv-libs, ffmpeg, ffmpeg-libs, libsndfile)
+- Added python-mpv, soundfile, numpy to pyproject.toml dependencies
+- Integrated MPVEngine into FastAPI lifespan with MPV_AO env var for configurable audio output
+- Implemented INF-03 as platform-guarded no-op (apply_timer_fix is Linux-safe)
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Add audio dependencies to Dockerfile and pyproject.toml** - `474b4a7` (chore)
+2. **Task 2: Create MPVEngine class with position polling and platform timer fix** - `5f75a19` (feat)
+
+**Plan metadata:** (committed with SUMMARY + state updates)
+
+## Files Created/Modified
+
+- `lightsync/audio/__init__.py` - Package marker for audio module
+- `lightsync/audio/engine.py` - MPVEngine class with headless mpv wrapper, 10Hz polling daemon thread, thread-safe get_state(), apply_timer_fix() INF-03 platform guard
+- `Dockerfile` - Added apk packages: mpv-libs, ffmpeg, ffmpeg-libs, libsndfile
+- `pyproject.toml` - Added python-mpv>=1.0.5, soundfile>=0.12.0, numpy>=1.26.0
+- `lightsync/main.py` - Import MPVEngine, create/start/stop in lifespan, expose via app.state.engine
+
+## Decisions Made
+
+- **MPV_AO env var** for audio output device: defaults to `null` (server mode, no speakers needed), overridable for local dev with actual audio output. This avoids hardcoding and keeps Docker images working without audio devices.
+- **Polling over observe_property**: observe_property fires on every decoded audio frame (~43x/s at 44.1kHz), which would flood the asyncio event loop. Fixed 100ms polling gives exactly 10Hz regardless of audio format.
+- **apply_timer_fix() as Linux no-op**: `timeBeginPeriod` is a Windows-only Win32 API (`winmm.dll`). On Linux, the kernel provides sub-millisecond timer resolution natively. INF-03 is satisfied as a platform-guarded stub.
+
+## Deviations from Plan
+
+None — plan executed exactly as written. The load() method follows the research correction noted in the plan (no wait_for_playback() call, using async mpv loadfile).
+
+## Issues Encountered
+
+None — all dependencies verified in research phase, implementation matched expected patterns.
+
+## User Setup Required
+
+None - no external service configuration required. MPV_AO env var is optional (defaults to "null" which works in Docker without audio devices).
+
+## Next Phase Readiness
+
+- MPVEngine is ready for Plan 02-02 (waveform extraction using soundfile/numpy added in this plan)
+- MPVEngine is ready for Plan 02-03 (WebSocket broadcast loop using engine.get_state())
+- engine accessible in all API route handlers via `request.app.state.engine`
+- Docker image will build with all required audio libraries once deployed
+
+## Self-Check: PASSED
+
+- lightsync/audio/__init__.py: FOUND
+- lightsync/audio/engine.py: FOUND
+- lightsync/main.py: FOUND
+- .planning/phases/02-audio-engine/02-01-SUMMARY.md: FOUND
+- Commit 474b4a7 (chore: audio deps): FOUND
+- Commit 5f75a19 (feat: MPVEngine): FOUND
+
+---
+*Phase: 02-audio-engine*
+*Completed: 2026-04-06*