Plan: phase 12 redesigned as a 10 s machine-readable sync burst decoded by the sweep into the timecode track; nothing visible in finals

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

CommunityDiscordMedia.md

@@ -287,27 +287,32 @@ Discord roles); the publish path must start with the user's own name.
 - [ ] dock + README; remove streamers from configure.py; delete `streamers.json`
 - [ ] test: OBS with an app password; Go Live with no key; a non-streamer gets denied
 
-### Phase 12 — timecode for multicam editing (frame accurate)  (planned)
-Target: clips from several streamers align to the frame (16.7 ms @60) on a multicam timeline.
-**Reference clock = the server** (NTP-disciplined). Recording start, the `tmcd` track and the burned-in clock
-all derive from it; streamer PC clocks are never trusted.
-Server-side stamping alone cannot do that (encoder + network delay differs per streamer by 0.1–0.3 s),
-so: a real timecode track for coarse placement + a capture-side reference for the frame.
-- [ ] MediaMTX `recordPath` with `%f` (microseconds) — paths section, hot-reloaded
-- [ ] sweep: on publishing a stream, write a QuickTime `tmcd` timecode track (start = Eastern time of day of
-      the first frame, file fps) and `creation_time` (UTC) metadata, inside the existing lossless remux
-- [ ] plugin `ItemTimestamp`: accept the microsecond filename; prefer `creation_time` when present
-- [ ] `/clock/` page on the main host (behind Authentik): HTTPS offset measurement to the server clock
-      (±few ms), 60 fps time-of-day readout with ms + once-per-second flash — add as an OBS browser source
-      for burned-in timecode (BITC) when shared audio isn't available; optional per streamer
-- [ ] dock: manage the OBS clock overlay via obs-websocket — CreateInput (browser_source → `/clock/`, sized for
-      the corner), SetSceneItemTransform for the chosen corner, SetSceneItemEnabled toggle, "add to this scene";
-      the browser source shares the dock's cookies so the Authentik login carries over
-- [ ] live portal Go Live: composite the captured window through a canvas and paint the server-synced clock
-      into a corner on every frame before publishing (toggle, default on) — burned-in clock on the WebRTC path
-- [ ] README: editor workflow — multicam: sync by timecode (coarse), then audio waveform (sample-accurate,
-      everyone is in the same voice chat) or the burned-in clock
-- rejected: LTC audio timecode per PC (needs SRT multitrack + a generator app on every machine)
+### Phase 12 — frame-accurate timecode for multicam, invisible in the footage  (planned)
+Target: clips from several streamers align to the frame (16.7 ms @60) on a multicam timeline, with
+**nothing visible in the finals**. Reference clock = the server; streamer PC clocks are never trusted.
+Key fact: a streamer's capture→server offset is steady for a whole stream, so it only has to be measured once.
+
+- **Sync burst**: for the first ~10 s of every stream, a machine-readable strip (black/white cells: server
+  time in ms + checksum + framing, ~400×16 px on a 1440p canvas, sized to the OBS canvas) is shown in a
+  corner, then hidden. OBS: the dock creates a `browser_source` → `/clock/` via obs-websocket and toggles it
+  on StreamStateChanged (on for 10 s, off). Go Live: painted into the canvas composite for the same window.
+  The `/clock/` page measures its offset to the server over HTTPS (±few ms) — the strip shows *server* time.
+- **Sweep**: when publishing a stream, extract frames from the first 10 s, locate + decode the strip in several
+  frames, median(decoded − pts) = server-clock capture time of frame 0 (frame-accurate). Write it as a QuickTime
+  `tmcd` track (time of day, Eastern, file fps) and `creation_time` (UTC) inside the existing lossless remux.
+  No strip found → fall back to server arrival time (coarse) and log it. Never re-encode, never crop.
+- MediaMTX `recordPath` with `%f` (microseconds) for the fallback; plugin `ItemTimestamp` accepts it and prefers
+  `creation_time`.
+- Editors: multicam → sync by timecode (now frame-accurate when the burst was present), shared voice audio as
+  the cross-check. Finals carry no overlay.
+- Streamer opt-out in the dock / Go Live (coarse timecode only).
+- [ ] `/clock/` page (server-offset measurement, strip encoder, optional human-readable readout)
+- [ ] dock: create/position/toggle the overlay source via obs-websocket; 10 s burst on stream start
+- [ ] portal Go Live: canvas composite with the burst for 10 s (toggle)
+- [ ] sweep: `bin/timecode-decode.py` (ffmpeg frames → decode → offset), tmcd + creation_time in the remux
+- [ ] MediaMTX `%f`; plugin timestamp update; README editor workflow
+- rejected: LTC audio (needs SRT multitrack + per-PC generator); permanent visible clock (in the finals);
+  cropping at remux (would force a re-encode)
 
 ### Option — more clip sources (Medal, Twitch/YouTube/Kick clips, Discord uploads)