Master clock: the selected soundtrack (new GET /api/audio/{id} —
listening-quality stereo AAC, lazily ffmpeg-extracted and cached in
data/work/audio_hq/) plays through WebAudio, and t_global derives from
AudioContext.currentTime. Every <video> is muted picture-only, so hard
seeks and playbackRate corrections are inaudible (the unmuted video
used to warble on every nudge). Graceful fallback to the old
performance.now() clock + <video> audio when a track can't load, with
an in-place upgrade if the decode lands mid-play. Drift is compensated
in the track's playbackRate; _resync() now recomputes from the live
clock since the soundtrack keeps playing while rAF is throttled.
Spatial audio (🎧 3D audio, shown when poses exist): every enabled
camera's track plays through an HRTF PannerNode at its live
reconstructed pose, gains normalized 1/sqrt(N); the listener follows
the viewer camera each frame (free roam, follow-cam, and M9 paths).
Tracks that finish decoding mid-play join the mix in place; toggling,
seeking, rate and enable changes rebuild the graph at the current
t_global with no timeline jump.
The window.__f4d debug hook is now also available in production builds
via localStorage f4dDebug=1 (headless panes throttle rAF; the pump is
the only way to drive the loop there).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Fills the foundation stubs in ingest.py and audio_sync.py.
- ingest: ffprobe probe + mono 16 kHz WAV extraction per video (ffmpeg);
idempotent run_ingest reuses existing rows so synthetic -> ingest -> sync
works without unique-constraint collisions.
- sync: PHAT-whitened GCC-PHAT pairwise offsets with sub-sample parabolic
peak refinement, scored by peak-to-second-peak ratio; confidence-weighted
global least-squares solve with cycle-consistency rejection (>50 ms);
windowed drift estimation (ppm) with a 5 ppm deadband; disconnected
sync-graph components -> offset_ms=None (spec pitfall #5).
- Persists offset_ms/drift_ppm/sync_confidence via db.update_video_sync and
exports data/work/sync.json.
Verified on the synthetic fixture: synthetic -> ingest -> sync recovers the
ground-truth offsets (0 / +1370 / -842 ms) to <0.001 ms and drift 0 ppm,
well inside the spec M1 tolerances (+/-10 ms, +/-3 ppm). pytest: 43 passed
(24 foundation + 19 new in test_ingest.py and test_audio_sync.py).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
