highascg

PGM look take — AMCP pipeline

POST /api/scene/take runs runSceneTakeLbg on the Caspar program channel (and optionally the paired preview channel). This document is the command order for a standard crossfade take to PGM.

Routing (channel 1 PGM, channel 2 PRV)

Step	HTTP / API	Caspar channel
Send look to preview	`POST /api/scene/take` with `"target": "preview"` (or `"bus": "prv"`) and `channel` = PGM (1)	Incoming look built on PRV (2)
Send look to program	`POST /api/scene/take` with `channel` = PGM (1), no `target`	Incoming on PGM (1); previous PGM copied to PRV (2)

Preview-only takes use skipLayerVisualEquality: true so layers always load even when live JSON already matches.

Physical layer banks (PGM)

Logical look layer N uses two physical layers on the same Caspar channel:

Bank	Physical layer	When
A	`N` (e.g. `10`)	Off-air or on-air depending on `programLayerBankByChannel`
B	`N + 100` (e.g. `110`)	Opposite bank

Rule: never MIXER FILL / MIXER CLEAR on the active (on-air) bank while preparing a new look. Incoming media is prepared on the inactive bank, then opacity crossfade swaps visibility.

Phase 0 — Planning (no AMCP)

diffScenes(currentScene, incomingScene) → exit / update / enter.
buildTakeJobs → per-layer LOADBG + mixer lines + PLAY plan.
Orphan layers still on Caspar but not in the incoming look are added to the exit list.
shouldRunBankCrossfade = transition duration > 0, previous look non-empty, not MERGE/+Animate.

Phase 1 — Exit fade (optional)

When there are exiting media layers, transition duration > 0, and no bank crossfade:

MIXER 1-<activeBank> OPACITY 0 <frames> <tween>
MIXER 1 COMMIT

Phase 2 — Stale off-air bank cleanup

On the inactive bank only, STOP + MIXER CLEAR any look-stack layer not in the incoming look (prevents leftovers after a prior swap).

Phase 3 — Global border (optional)

CG ADD / UPDATE on layer 998 (or 996), sometimes at opacity 0 before a linked fade.

Phase 4 — Per incoming layer (inactive bank)

For each layer in the incoming look (example: logical 10 → physical 110 when bank B is inactive):

MIXER 1-110 CLEAR
LOADBG 1-110 "clip.mov"
MIXER 1-110 OPACITY 0 0          # only when incoming is the top layer (bank B)
MIXER 1-110 FILL <x> <y> <scaleX> <scaleY> 0
MIXER 1-110 ROTATION <deg> 0
… other DEFER mixer lines (volume, keyer, effects) …

When incoming is on bank A (under outgoing bank B), prep uses MIXER 1-10 OPACITY 1 0 instead of hiding — incoming must be full opacity under the top layer.

Then PIP overlay CG lines if configured.

Important: When incoming is on top, OPACITY 0 0 is sent before FILL so geometry changes are not visible on program during prep.

Phase 5 — Bank crossfade + PLAY (when `shouldRunBankCrossfade`)

After a short preroll (~80–180 ms when incoming is pre-hidden; ~80 ms when incoming is underneath).

Case A — incoming above outgoing (on-air 1-10, incoming 1-110):

MIXER 1 COMMIT
PLAY 1-110
MIXER 1-110 OPACITY 0 0
MIXER 1-110 OPACITY 1 <frames> <tween>
MIXER 1 COMMIT

Outgoing 1-10 stays at full opacity; teardown clears it after the fade window.

Case B — outgoing above incoming (on-air 1-110, incoming 1-10):

MIXER 1 COMMIT
PLAY 1-10
MIXER 1-10 OPACITY 1 0
MIXER 1-110 OPACITY 0 <frames> <tween>
MIXER 1 COMMIT

Incoming 1-10 is already at full opacity under 1-110; only the top layer tweens.

Phase 5b — Cut / no crossfade

MIXER 1 COMMIT
PLAY 1-110
MIXER 1 COMMIT

Phase 6 — Teardown (after fade time)

STOP 1-10
MIXER 1-10 CLEAR
MIXER 1 COMMIT

Bank pointer flips: inactive becomes active for the next take.

`+ Animate` path (same on-air physical layer)

No bank swap. Incoming uses phys(N, activeBank) — the layer currently on program (e.g. 1-110 when bank B is on air).

Phase A — Prepare

LOADBG 1-110 "example2.mov" LOOP …
MIXER 1-110 FILL <x> <y> <sx> <sy> 75 linear
MIXER 1-110 ROTATION … 0
… KEYER / VOLUME / effects (DEFER) …

No LOADBG MIX. No MIXER OPACITY <dur> on the on-air layer (Caspar PLAY … MIX owns the dissolve).

Phase B — COMMIT sandwich

MIXER 1 COMMIT
PLAY 1-110 "example2.mov" MIX 75 linear
MIXER 1 COMMIT

FILL duration/tween matches PLAY transition frames/tween.

Phase C — Teardown

After fadeMs: clear inactive bank ghost for updated layers; STOP/CLEAR true exits on both banks. programLayerBank unchanged. Then PGM→PRV exchange (routes-scene.js).

PGM + PRV dual-channel summary

Preview (target: "preview"): phases 0–6 on PRV only (uses forceCut from the request unless you need a faded preview).
Program (default): hard-cut incoming onto PRV first (forceCut: true always), then run the look transition on PGM only. Set stageOnPreview: false to skip PRV staging. After PGM take, previous PGM is copied onto PRV (hard cut).

What causes visible FILL changes (avoid)

MIXER FILL on the active bank during prep.
Animated MIXER FILL with a non-zero duration on an on-air layer (MERGE path).
FILL before OPACITY 0 on the incoming (off-air) layer.

Current code applies immediate FILL (tail 0). The inactive bank is hidden with OPACITY 0 0 only when it is the top layer (bank B); when incoming is bank A, it is set to full opacity before PLAY.

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