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>
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