festifun/plan/status/lane-C.md

Status — lane-C

Round 1 — 2026-07-16 — STATUS: in_progress

Directives acknowledged: round 0 of plan/DIRECTIVES.md (run order C→A→D→B; C starts first as the longest lane + earliest API-contract validation; merge when acceptance passes, don't wait on siblings; maintain this status file; evidence discipline — a checked box names the test/command+output that proves it).

Acceptance checklist (lane brief M4/M5/M6 + timeline markers):

• M4 — synchronized playback: master clock; per-video correction (hard-seek >150ms, nudge playbackRate 20–150ms, lock <20ms); out-of-range videos pause+dim; one audio source; dev overlay per-video sync error stays <50ms during continuous playback.
• M5 — 3D viewer: PLY point cloud; per-video camera-path lines + current-pose frusta (colored); OrbitControls; snap-to-camera (intrinsics→PerspectiveCamera) matches the video; free-roam detaches. All COLMAP→Three via frozen lib/pose.js.
• M6 — anchor overlays: per-video transparent canvas, letterbox-correct; project each anchor via pose.js camera; skip if behind (z_cam<0); corners track the stage box in all 3 videos while playing.
• Timeline event markers: GET /api/events as colored markers (color by event_type, legend); hover tooltip; click-to-jump.
• App runs against synthetic data with no console errors; merged to main.

Done this round (session start): verified environment and the frozen contracts against the live server (python -m festival4d serve): manifest (3 videos, offsets 0/+1370/−842 ms, t_global_max 21.37), 41 registered poses/video keyed by frame_idx (centered intrinsics fx=fy=554.26, cx=320, cy=180), 4 stage-corner anchors, 7 typed events, Range→206, colored PLY (3106 pts). Independently verified stage-corner projection lands all 4 corners in-frame, in front of the camera, for all 3 videos (cam0 left, cam1 front-center, cam2 right; centers on an arc at radius ~9.5) — so M5/M6 geometry is sound before writing render code.

Blockers / questions for coordinator: none. No change requests — the frozen API/pose/ timebase contracts are sufficient for the whole lane as-is.

Next: build in dependency order — state → transport (verify M4 + dev sync overlay first, per brief) → videoGrid → timeline → scene3d → overlays; verify live in-browser; adversarial review pass; merge.