embedded-captions

name

embedded-captions

description

Add captions or subtitles to an existing single-subject talking-head video without editing the footage. Use for plain verbatim captions, cinematic captions embedded behind the subject, VFX captions, “炸/特效/酷炫字幕,” or a named identity from the 35-style catalog. Route by visual identity, not by backend engine. The quiet `anchor` rail is the default; embed every word only when the user explicitly wants a fully cinematic treatment. The workflow runs locally end to end, including transcription and subject matting; split multi-shot footage before applying it.

First, keep this skill fresh — confirm with the user before running: npx hyperframes skills update embedded-captions. A fast no-op when everything is current; otherwise it refreshes this skill plus the core domain skills it depends on before you rely on them.

Embedded Captions

One catalog, picked up front (CATALOG.md — 35 identities; the engines behind it are backend detail). Standard (default) builds a clean verbatim rail (lower-third subtitle carrying most text) + an embed climax composited into the scene behind the subject at the peak. Cinematic is pure embed — no rail, every caption composited behind the subject (hero typography, accumulation, occlusion as the effect). Theme is a complete themed constitution — body paradigm × hero setpiece × front fx × plate reaction, composed from registries (themes/README.md): ordnance terminal neonsign stardust stomp. Most explainer / voiceover is Standard; embed is the scarce, earned peak — embedding every word is the common mistake; Theme is for VFX-grade asks ("炸", "特效", "像 AE 做的").

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Operational flow (TL;DR)

Routed through /hyperframes, the intent layer confirms only the input (which clip) and announces the identity pick as a deferred ask — the shortlist needs the probed clip, so it stays at step 1 below; the layer's run-shape questions don't apply (the footage is untouched, there is no storyboard to review). A BRIEF.md, when present, carries the confirmed input and any user notes — read it first.

The craft prose below is long; the pipeline itself is short — and everything deterministic is computed or compiled, never hand-written:

1. Decision gate (refuse bad clips) → pick ONE identity from CATALOG.md (35 identities; engine/compiler derived by lookup — never surface a mode/category question)
2. hyperframes init (skip it if the project dir already exists with the video inside — matte.cjs/transcribe.cjs adopt any video in the dir as source.mp4) → bash scripts/prepare.sh <project> (matte ∥ transcribe ∥ audio-envelope in parallel, then safe-zones v2 with scene palette/optics/lighting — one command, nothing forgotten)
3. author a small JSON of creative choices (read safe-zones.json first): Cinematic → plan.json → fill-timings.cjs → fit-fonts.cjs → make-composition.cjs; Theme → theme.json → make-theme.cjs (rail/panel/poem/takeover paradigms; anchor is the quiet rail default)
4. Visual QA: node scripts/preview-frames.cjs <project> → faithful composite previews in ~2s/frame (no render). Check § Visual QA before paying for a render.
5. render-and-composite.sh → gates (timing / occlusion+hero / overflow / hand-off) → final.mp4

Load-bearing rules people miss:

• rail (default) + embed (promotion). drop (filler, not shown) / rail (verbatim lower-third subtitle, in front, carries most text) / embed (a peak word composited behind the subject). Standard mode does both, embedding only the peak(s). See § Caption model.
• The video is delivered UNTOUCHED (Standard/Cinematic; Theme mode's PLATE budget is the one sanctioned exception — register-gated reaction beats (charge-dim, punch, shake, grain) defined per theme DNA and applied AFTER the matte composite so subject+text+plate move as one frame) — captions are the only thing added; the matte just lets the subject occlude the embed track. Never grade/recolor/scanline the footage.
• Two rulebooks: rail → references/rail.md (thin), embed craft → references/composition-craft.md (rich, embed-only). Skim by need.

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Caption model — rail + embed

Every spoken phrase is one of three things:

	What	How it's shown
drop	filler — um/uh, stutters, self-corrections	not shown
rail	the default — ordinary spoken content (verbatim)	clean lower-third subtitle, in front, readable. A punch word can get an inline emphasis highlight (accent colour / active-word pop) — it stays on the rail.
embed	a promoted peak — the headline beat	one big word composited behind the subject (matte occlusion), designed entrance + exit

The rail carries most of the text; embed is the scarce, earned peak. Scarcity is per beat/block, not per clip: ≤1 hero per block (thought), never two co-visible, ≥ a beat of air between hero windows (the compiler warns under 0.6s). A short clip → usually 1–2; a long explainer → ~one per section. Among multiple heroes, the largest authored one is the APEX (it alone gets the full lockup embed + width-fit raise); smaller ones are MINOR peaks that ride their column as oversized emphasis lines (fg, damped motion) — not every beat needs the matte showcase, which is exactly what keeps the apex an event. Embedding every word is still the common mistake.

Rail-surface identities build exactly this (rail = rail.html, embed = the climax in index.html). Column-flow identities drop the rail and make everything embed-style — recommend them only for mood-over-verbatim asks, never for explainer / voiceover where the words must read (CATALOG.md encodes this per identity).

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Step 0 — pick ONE identity from the CATALOG

One front-end, three engines behind. The user picks an IDENTITY from CATALOG.md (35 entries: 10 classic + 25 themed); the engine, compiler and authoring file are derived by lookup from the catalog row. Never surface "Standard vs Cinematic vs Theme" as a question — those are backend names (a product has one UX even with several engines). The catalog encodes everything routing needs: reading surface, voice, recommend-for, scene needs, adjacency notes for the genuinely-close pairs (loud↔ordnance, neon↔neonsign, cream↔stardust).

The identity pick is a preference gate (../hyperframes-core/references/brief-contract.md § 1): in autonomous mode ("surprise me" / "decide for me"), pick from your shortlist yourself and state the one-line why instead of asking.

Procedure: probe the clip → shortlist 2–3 identities from the catalog → recommend ONE with a one-line why → the user picks (autonomous mode: you pick, stating the why) → author that identity's file. Identities are engine-locked (no cross combos; opening one is a validation event — see dna/README.md).

Always present your recommendation and let the user pick before you author. Don't silently default.

(The full identity table lives in CATALOG.md — single source of truth for routing. The engine docs below describe each backend's authoring contract.)

Recommendation heuristic: use the "Shortlisting heuristics" in CATALOG.md — they are identity-level (e.g. "炸" shortlists ordnance/stomp/terminal/loud and picks by WHAT should explode), never category-level. Unsure → anchor.

• Cinematic → write plan.json for a locked template, compiled by make-composition.cjs.
• Theme → read themes/README.md, author theme.json, run scripts/render-theme.sh (compiles + renders + plate reaction → final_fx.mp4).

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Decision gate — RUN FIRST

Probe the video and classify the scene before either mode.

ffprobe <video.mp4>                    # specs
ffmpeg -ss <t> -i <video.mp4> -vframes 1 sample.png   # at 20/50/80%

Read the samples. Refuse if:

• Multiple speakers / hard cuts (split & render each shot, or refuse)
• No human subject (this skill is for talking-head)
• Under 3 seconds, no speech, or face never clearly visible — transcribe.cjs warns when audio is near-silent (Whisper hallucinates words like "Thank you." over silence); heed it and refuse rather than caption fabricated words
• Source already has burned-in captions / subtitles / heavy text graphics — adding a second caption system conflicts and the footage ships untouched (no covering/inpainting). Burned text often appears only mid-clip: sample a 1fps contact sheet (ffmpeg -i in.mp4 -vf "fps=1,scale=160:-1,tile=10x5" sheet.png), don't trust 3 spot frames.
• Transcript is garbage — non-native/heavy-accent speech can transcribe into confident gibberish. Sanity-read transcript.json before authoring; if it doesn't parse as language, try WHISPER_MODEL=medium once, else refuse (a verbatim rail of fabricated words is worse than no captions).
• Busy handheld with fast motion (matte flickers)

Pre-flight probes (cost nothing, prevent the worst failures)

1. Shot-cut probe. Sample frames at 20%, 50%, 80%. If a different subject/scene appears, trim the clip before the cut.
2. Letterbox / pillarbox probe. Black bars on the first frame? Compute safe content rect and constrain caption placement inside it.
3. Luminance probe. Sample the caption region's average luminance — under 60 → light text reads as-is, 60-180 → add the glyph scrim, 180+ → opaque text + scrim (never bare light text). Cinematic templates are cream+screen and LOCKED — use this probe to pick a fitting identity (bright scenes → ink, or the opaque-rail anchor theme), never to recolour one.
4. Identity recommendation by tone (you recommend; the user picks — see Step 0 + CATALOG.md). explainer / interview / must-read words → rail/panel-surface identities; poetic / social / "cinematic" → column-flow identities by register; "炸 / 特效 / VFX" / named worlds → themed identities. When unsure → anchor (words read, scene safe) — but present a shortlist and let the user choose.

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Pipeline — 5 steps

1. hyperframes init <project> --non-interactive --video <video.mp4> --skill=embedded-captions
2. bash scripts/prepare.sh <project>       # matte ∥ transcribe (parallel) → safe-zones. One command.
                                           #   → frames_fg/ transcript.json safe-zones.json
3. [AGENT STEP — the only creative step] author a small JSON; see below by mode
   Cinematic: author plan.json → node scripts/fill-timings.cjs → fit-fonts.cjs → make-composition.cjs
   Theme:     author theme.json → bash scripts/render-theme.sh <project>   (compiles + renders + plate fx)
4. node scripts/preview-frames.cjs <project>   # ~2s/frame composite previews → § Visual QA (BEFORE the render)
5. bash scripts/render-and-composite.sh <project>  # gates → final.mp4 + history/ snapshot
   (Theme mode: SKIP steps 3b/5 — render-theme.sh already runs compile + render-and-composite
    + _postfx.sh; the deliverable is final_fx.mp4, final.mp4 is pre-plate-reaction)

Step 1's init checks the installed skills against the latest on GitHub and updates the global set if any are out of date.

Step 3 differs by mode:

Step 3 — Cinematic mode (pure embed)

1. Read safe-zones.json first. Narration planes go in zones.hugLeft/hugRight — clean strips ABUTTING the silhouette (text far from the body reads as floating, not embedded; far corners are the fallback, not the default). The hero defaults to heroAnchor/heroBands.best (centered ON the subject, ~30–55% occluded). recommendation:"fg" moves NARRATION in front for legibility; the hero stays embedded whenever heroBands.feasible — hero-fg is the last resort.
2. The DNA is the identity you picked in Step 0 (CATALOG.md) — do not re-open the choice here. Sanity-check it against the scene (bright hero band luma > 150 wants ink; full pick guidance lives in the catalog, covering all ten incl. neon / glitch / chrome / velocity). State your pick + why; the user decides. The DNA locks type/palette/blend/motion + hero three-act; safe-zones v2 (palette/optics/lighting) parameterizes it to THIS scene automatically.
3. Author <project>/cinematic.json — "dna": "<name>" + thought-BLOCKS, not raw groups: each block = lines of words (grouped 2–5 at clause boundaries) + the plane it stacks in + per-line css (size/weight/style only — no positions) + at most ONE line marked "hero": true (the promoted word; "text" for display form). Schema: scripts/make-cinematic.cjs header.
4. Compile: node scripts/make-cinematic.cjs <project> — lowers blocks → plan.json → index.html. Generated for you: transcript-sequenced timings, accumulate-within-block, page-flip-between-blocks, the hero LOCKUP (a hero block's pre-context, HERO and post-context stack as ONE bonded composition centered on the subject — reading order top→bottom = spoken order by construction; context floats in FRONT while the hero embeds BEHIND = the depth sandwich; a mass rule keeps the hero dominating its context), apex/minor hero split, reading order by construction, fg fallback per safe-zones. Then the gates run as usual. (Hand-authoring plan.json directly remains possible for designs blocks can't express — then run fill-timings.cjs + fit-fonts.cjs + make-composition.cjs yourself.)

Step 3 — Theme mode (themed constitution)

Read themes/README.md FIRST — paradigm/setpiece registries, linkages, hard rules, and the exact theme.json schema.

1. Pick a theme DNA by content register (each themes/<name>.json has voice + when). State your pick + why; the user decides.
2. Author <project>/theme.json — dna, lines (verbatim, transcript order; 1–5 words each — for takeover each line is one CARD), minors (emphasis words), hero:{match} (the climax word/phrase; leave it OUT of lines for embed setpieces, keep it IN for inline setpieces and panel+redact).
3. Render: bash scripts/render-theme.sh <project> — compiles (verbatim-completeness gate at compile time), renders both layers, composites, applies the plate reaction → final_fx.mp4. Use preview-frames.cjs between compile and render for Visual QA.

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Visual QA — preview BEFORE you render

node scripts/preview-frames.cjs <project> [t…] composites faithful preview frames in ~2s each (caption layers screenshotted at seek-time + real video frame + matte occlusion + rail overlay = what the final composite will look like at that moment). Default samples = each group/climax window. A full render costs minutes — never use it to discover layout problems.

Check the previews (<project>/preview/sheet.png) against this list — these are the failures the geometric gates cannot catch:

1. Washout — light text over a bright region (window/sign/sky): unreadable → move the plane or change DNA/mode (bright scene → ink).
2. Text-on-text — captions over the scene's own text/graphics, or two caption groups colliding.
3. Reading order — on-screen vertical order must match spoken order; the hero must not sit below later words.
4. Hero presence — the climax should be BIG and visibly behind the subject (~30–55% occluded), not a floating label in a margin.
5. Balance — one coherent column/band, not scattered fragments; margins breathing; nothing clipped.

Then the 5 positive checks in references/reference-bar.md (poster test · timid test · one-glance hierarchy · scene handshake · dead-air audit) — the failure list keeps a render from being broken; the positive list is what makes it designed. Ship when both pass.

Fresh-eyes review (recommended for anything user-facing): you have confirmation bias about your own layout. If you can spawn a subagent, give it ONLY the preview sheet + this checklist and ask for PASS/FIX verdicts per frame ("review these caption previews against the 5-point checklist; answer PASS or the specific fix per frame"). Apply fixes in plan.json / theme.json, recompile, re-preview — each loop costs seconds. Render once, when the previews pass.

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The DNA registry — ten visual languages (replaces the template catalog)

Both modes draw from dna/ — ten art-directed visual languages that parameterize per scene (accent sampled from the footage, contact shadow along the measured light direction, depth-match blur, RMS-coupled hero amplitude):

DNA	Register	Scene fit	Voice
cream	premium-warm	dark/mid warm scenes	Inter + warm cream + screen; glowing emergence hero (successor of cinematic-cream)
ink	premium	bright scenes (luma > 150)	near-black multiply — type printed ON the wall; the bright-scene answer
editorial	editorial-luxe	introspective / fashion / poetic	Bodoni Moda, lowercase-italic hero — magazine elegance
keynote	tech-premium	product / launch	opaque white Inter 800, dead-center stillness
documentary	formal	interview / serious	burn-in reveals, no hero — gravitas IS the style
loud	loud	hype / sport / social	Anton + scene-sampled accent, single-unit slam + ripple; body ANNOUNCES in front (bodyLayer: fg)
neon	loud-neon	neon-noir / nightlife / tech-noir (dark scenes)	electric-cyan signage, ignition flicker, the hero powers ON like a sign
glitch	loud-neon	digital / hacker / AI	RGB-split echoes snap together on landing; machine-percussive timing
chrome	loud-luxe	Y2K / fashion-tech / music	liquid-metal gradient hero + one sheen sweep during the hold
velocity	loud-sport	sport / auto / fitness	every word arrives along its motion vector (streak+skew), hero passes with speed trails

Pick by safe-zones.json (heroAnchor.bandLuma, palette.temperature) × content register — dna/README.md has the decision rule. Authoring: cinematic.json takes "dna": "<name>".

The engine generates the hero three-act from the DNA (no authoring needed): co-visible captions dim (setup) → per-letter entrance with amplitude ∝ spoken loudness (impact) → breathe + glow until exit (afterglow).

(Legacy: plan.template:"cinematic-cream" maps to dna:"cream" automatically. The retired 54-template library is archived outside this repo and is not distributed with the skill; _motion.md remains in-skill as the motion-verb reference catalog.)

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Aesthetic decision — tone × shot × platform (input to the catalog shortlist, NOT a second router)

Classify the clip on 3 axes and feed the result into CATALOG.md's shortlisting — this section never picks a mode/engine by itself:

Tone (what feel does the content have?)

• documentary | conversational | energetic | poetic | keynote | investigative | music-video

Shot (what's the framing?)

• close-up (head + shoulders) | mid-shot (torso+) | wide (full body+) | cut-montage (mixed shots)

Platform (where will it play?)

• 9:16 portrait (TikTok/IG/Shorts) | 16:9 landscape (YouTube/web) | 1:1 square | broadcast export

Cross-reference in references/direction-catalog.md § Classification matrix for direction language — then return to CATALOG.md to shortlist identities (this matrix informs the shortlist; the catalog is the only routing surface).

Composition craft (embed track) — read before embedding

The full embed-track playbook lives in references/composition-craft.md: transcript role-annotation, phrase grouping, planes & clean-zone anchoring, zone coherence, climax pop & readability, edge-breathing, the occlusion 3-step judgement, and accumulation/persistence. It governs how a promoted phrase sits INTO the scene — read it before authoring any embed (Cinematic plan.json or Standard index.html). The default rail track has its own, much simpler spec → references/rail.md.

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Shared knowledge

Doc	What
references/rail.md	The rail track — standard lower-third subtitle spec (the default; carries most text).
references/composition-craft.md	The embed-track playbook — grouping, planes, climax pop, occlusion judgement, accumulation/persistence. Read before embedding.
dna/README.md	The DNA registry — ten scene-parameterized visual languages; how to pick.
references/reference-bar.md	The taste bar — per-register world-class references + the 5 positive checks.
references/aesthetic-principles.md	The 18 rules. Beat Veed AI on taste. Read first.
references/motion-vocabulary.md	10 named motion primitives + tone→timing lookup
references/direction-catalog.md	10 ship-ready aesthetics + tone×shot×platform matrix
references/anti-patterns.md	Bugs already locked out (CoreML, letter-spacing reflow, etc.)
references/scene-types.md	When a wall surface is usable (4 conditions)
references/layout-heuristics.md	Plane positioning, clean-zone selection, crown 3 conditions, pillarbox math
references/typography-presets.md	Font-size × column-width matrix (starting points)
references/caption-grouping.md	Word → group rules (pauses, sentence boundaries)
references/failure-modes.md	Long tail of dev gotchas
references/bespoke-vs-presets.md	Why presets fail sometimes; clone-and-tweak pattern

Read the aesthetic principles and direction catalog FIRST. Everything else is implementation detail.

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Non-negotiables

• Face must never be 100%-covered continuously — every 0.3s window, face bbox ≥30% uncovered.
• WCAG contrast — final render lints; fix palette if it fails.
• Deterministic — no Math.random(), no Date.now(), no repeat:-1.
• Never grade/recolor the video. The footage ships untouched — captions are the only addition. No full-frame scanlines / duotone / darken / vignette over the a-roll. neon-noir/CRT texture belongs inside a caption element, not over the whole frame.
• Rail-first for talking-head / explainer. Don't embed the whole transcript — most text is the rail; embed only peaks. Embedding everything is the default mistake.
• Embed is scarce + spaced. ≤1 embed per sentence/beat, never two adjacent or co-visible, ≥ a beat apart, at most one apex. climax = per-beat peak, not "the single payoff of the entire clip."
• Matte = the PERSON (hyperframes remove-background, u2net_human_seg, Apache-2.0). Human segmentation by intent, but not surgically: thin offset furniture (mic boom arms) is usually excluded — captions render over it, behind the person — while large salient objects NEAR the subject (a telescope, a desk rig) can still leak into the matte and occlude captions. Objects HELD by the subject (products, phones) may drop out intermittently, letting captions pass in front. NEVER assume: sample frames_fg/ at 2-3 timestamps before placing the hero, and prefer hero positions clear of any leaked furniture (heroAnchor can be skewed by leaks — cross-check against frames_bg).
• safe-zones is PROP-BLIND — eyeball every band you use. Zones/heroBands score subject occlusion + luma only: a mic, telescope, or screen sitting inside a "clean" zone is invisible to them (and a prop leaking INTO the matte skews heroAnchor.centerXPct off the person). Before authoring, extract ONE frame of each band you intend to use; if a prop lives there, measure its bbox and move/shrink the plane. Two real cases shipped clean only because the agent did exactly this. (Auto prop-saliency is a known gap; zones' peakLuma only catches moving bright objects.)
• Captions stay on-frame. Cinematic mode hard-gates frame-overflow; Standard mode runs check-overflow.cjs as a WARNING (intentional bleed is the only exception — read the warning).
• Each caption ≥ 0.5s on screen — shorter = unreadable.

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Dependencies

• hyperframes, built (packages/cli/dist/cli.js). Scripts auto-resolve the checkout: HYPERFRAMES_ROOT env → repo root if this skill ships inside hyperframes → ~/Downloads/hyperframes. Build with bun install && bun run build.
• Node-first; two Python touchpoints via uvx (no manual installs): transcription runs WhisperX through uvx (word-level timings; falls back per SKILL §transcription), and Theme's drawon setpiece shells python3 scripts/gen-stroke-path.py at compile time. Everything else runs on the toolchain hyperframes already ships: matting via the hyperframes CLI's remove-background (u2net_human_seg; weights auto-download once, ~168 MB, to ~/.cache/hyperframes/), image/alpha math via sharp, layout/occlusion/overflow via puppeteer, plus ffmpeg. The scripts auto-resolve these from the hyperframes checkout — nothing extra to install.
• Transcription = WhisperX via uvx (word-level timings + alignment; no manual install — transcribe.cjs drives uvx whisperx). Falls back to an existing word-level transcript.json if present.
• Source video — matte.cjs / transcribe.cjs auto-resolve source.mp4 (or glob the clip / read hyperframes.json), so hyperframes init --video X.mp4 needs no manual rename.
• fps — matte.cjs extracts at the source's native rate and records matte.fps; render-and-composite.sh uses that so the matte stays frame-aligned.
• Matting weights are NOT bundled: matte.cjs shells the hyperframes CLI's remove-background, which downloads u2net_human_seg (~168 MB, Apache-2.0) once to ~/.cache/hyperframes/background-removal/models/. First prepare on a fresh machine needs network for that one download.

If a hard dependency is missing, STOP and ask the user — don't silently skip steps.