Shorts motion skill

shorts-motion

Stage 4 of shorts-edit. Scout → Plan → Render → Verify. Never skip the scout.

The pipeline already composites a per-frame RGBA sequence for captions, which means it is already a motion-graphics engine: anything drawable in PIL can be animated at frame resolution with no extra ffmpeg input and no extra encode.

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The three rules that make a graphic land

1. ANCHOR TO THE WORDS, NEVER TO A TIMESTAMP.

Hand-typed times failed catastrophically and invisibly: six of eight graphics were out of sync and one revealed the "F" tier grade 5.7 seconds before he said it. In a tier list the grade IS the punchline. Every frame was individually correct; nothing flagged it.

The plan names a phrase, not a time. resolve_cue() finds when it is spoken and fires the payload — the grade filling, the number landing — exactly on the word.

{ "cue": "definitely f tier", "grade": "F", "label": "Instagram / TikTok" }

2. OVERLAY PANELS, NOT FULL-SCREEN CARDS.

A full-screen card doesn't add a graphic — it removes the presenter, and on a talking-head short the face is what carries it. Panels sit in the lower third; he stays on camera. Full-screen is reserved for a genuine chapter break or a hook.

3. THE MOTION MUST TRACK THE SPEECH.

A card that fades in is a slide. A number that counts up and lands on the word, a list that builds as he names each item, a tier chip that fills the instant he says "S tier" — those feel authored. Everything else feels pasted on.

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Scout first — do not invent moments

python $S/motion_scout.py "<clip>"

It surfaces where a graphic would actually earn its place: hard numbers, enumerations, rankings, named tools. On the reference session it found one clip was a tier list (8 verdicts), another a 5-step system with a 0→300 users target, another carrying 14% / 11% / 0.5% reply rates. Content that was invisible to a blind pass.

Copy is editorial, never generated. Auto-deriving it from the transcript produced headlines like "step number five is actually relaunching your saas every two weeks with a launch". A bad graphic is worse than none. A clip with no plan entry simply gets none.

Primitives (motion.py)

kind	use for	motion
stat	a hard number	counts up and lands on the word
steps	an enumeration	rows build one at a time; the live row goes bold + emerald
tier	a ranking	chips greyed, the called grade fills emerald and pops
label	anything else	a lower-third chip — the lightest touch
logo	naming a product	brand mark parks just above the caption band
people	real accounts	profile cards, follower counts counting up
chips	a list of sources	small title-only cards landing left to right
leads	a lead table	LinkedIn rows stream, then the scores land on a second cue
flow	a routing decision	lanes greyed; each fills, and its wire draws, on its own cue

Everything except stat/table hangs off a y=470 baseline, which stops 29px clear of the caption band. Panels built that way need no caption lift and no caption hide — the captions just keep running. hide_frames had been applied to every mid-frame panel, which cost the Lovable clip 13 of its 73 seconds of captions to a collision the geometry ruled out.

Nested cues — when one panel spans several beats

A graphic that stays up across a long beat (the routing board: tier 1 at 28.0s, tier 2 at 30.1s, tier 3 at 34.3s) cannot stagger its rows off a frame counter — the stagger drifts the moment the speech does, which is the same class of failure as a hand-typed timestamp. Give each row its own cue; resolve_plan() resolves it to _at, in frames relative to the panel's window.

{"kind": "flow", "cue": "hand over all the", "dur": 12.6, "lanes": [
  {"cue": "tier one leads", "badge": "TIER 1", "to": "Sales team", "focal": true},
  {"cue": "tier two",       "badge": "TIER 2", "to": "Sequence", "tiles": ["...linkedin.png"]}
]}

A <name>_cue key on the graphic itself resolves the same way, to _at_<name>. That is how the lead table's grades wait for "score them against their ICP" instead of firing on the panel's own entrance four seconds earlier.

A primitive's payload is not always 0.7s after its entrance

LEAD/PAYLOAD encode one choreography: the panel arrives, then the number lands on the word. logo and chips have nothing that lands later — the mark appearing IS the payload. verify_motion.py assumed the PAYLOAD model for every kind, so holding a logo to "entrance + 0.7s == the word" pushed its entrance 0.7s ahead of the word. The Lovable mark sat on screen most of a second before he said "Lovable", and every run reported ok.

A verifier that models one primitive's choreography and applies it to all of them certifies the bug. ENTRANCE_IS_PAYLOAD in verify_motion.py is the per-kind offset; multi-lane boards skip the single-payload check and verify each lane's own cue instead.

New primitives must also be added to brand_lint.py's render list. Three shipped outside it once, which meant the one-green rule was enforced on the four oldest renderers and silently not on the newest.

The tier board (tierboard.py)

A different shape: one persistent, cumulative board, not eight panels flashing in and out. The hook shows the finished board with the lane contents blurred (tease the payoff, don't give it), then each channel drops onto its row as he says the grade. The viewer watches it fill in. That is the tier-list format.

It occupies the lower ~40%, so the captions lift to 60% height for exactly those frames rather than being hidden for 100 seconds.

A panel and a caption cannot share a row

Captions sit at 0.78H (y≈499). A stat panel starts at y=446, a steps panel at y=422. So a caption lands inside the panel, and white type on a white surface is invisible at full opacity.

The tier board already lifted the captions to 0.60H. Nothing lifted them for the other primitives, and it shipped — because a caption over a half-faded panel is still legible, so it looks fine in exactly the frames you happen to spot-check.

Any frame carrying a stat or steps panel lifts the captions to 0.60H. label is exempt: its chip sits at 0.86H, ~40px clear of the caption band.

build.py resolves the plan before caption_frames() and unions those windows into raise_frames. Order matters: the captions have to know about the panels before they draw.

label() accepts a kicker and does not draw it

The chip is one line by design; a kicker row would make it a panel. The argument stays in the signature so every primitive takes the same plan shape — but it is silently dropped, and that silence once cost a whole batch its step numbers. If you want the kicker seen, put it in text: "01 · Build in public".

Brand — do not invent values

From gtm-production/brand/BRAND.md:

surface #ffffff · ink #0a0a0a · muted #71717a · line #e4e4e7 · accent #10b981 (ONE dot, sparingly)
font-sans Helvetica Neue (the same face as the captions) · radius 6/10/14/20
"everything is ink, surface, and line" — no shadows, no gradients.

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Retention: the 2026 five-second rule

Any 5-second block with no cut, zoom, text or sound change is a retention leak.

The reference clip failed badly: 97 of 107 seconds (91%) sat in a dead block, the worst a 16.8-second stretch. All the cuts and graphics clustered at beat boundaries, and beats run 11–17s.

Fix: automatic pattern interrupts. plan_chunks() splits long beats into ≤4.8s chunks with alternating framing — a snap change of camera mid-sentence. It is not a cut; the audio runs straight through. 18 interrupts, leak 91% → 0%.

Two things this depends on:

• Fades only at real cut edges. A 30ms fade at a framing split dips the voice audibly. Verified: 0 discontinuities across all 18 internal joins.
• Use ceil for the chunk count. Floor-plus-fudge left 5.7s chunks — still a leak.

A 3px drawbox progress bar is available (--progress) but is off by default — it reads as UI chrome bolted onto the frame. Cheap is not the same as good.

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THE RENDERING TRAP: PIL alpha does not composite

ImageDraw with a partial-alpha fill OVERWRITES pixels. A chip fading in therefore punches a transparent hole straight through the white panel beneath it, and the video shows through — the selected tier chip rendered as a black box instead of a green one.

Draw everything at full opacity on its own layer, then fade the layer. Never draw with a variable alpha. To animate a colour, LERP the colour — not the alpha.

Text behind the subject

The "he's standing in front of the word" look. behind.py. Composite order per frame:

video  ->  big text  ->  the person, cut back out on top  ->  captions + board

Two things make it work:

1. It stays inside ONE encode. The naive way is a second pass (render, re-read, segment, re-encode) — and a second encode measurably softens the image. Instead the person is baked into the same per-frame RGBA overlay the captions use, cut from the raw source frames that ffmpeg is already decoding. The cut-out lands on top of itself: no seam.
2. Any chunk carrying a behind-text is forced to wide. A zoomed chunk is scaled by zoompan inside ffmpeg, and re-deriving that transform in PIL would never match pixel-for-pixel — you would get a soft double-edge around him.

Layer order is the whole trick. Compositing the person LAST put his shoulder on top of the tier board and clipped the lanes. The person goes UNDER the UI: word, then him, then captions and board.

Segmentation: rembg (u2netp), ~0.2s/frame. Use it on 2-4 hero moments, not the clip.

"behind": [{"cue": "for sure s tier", "text": "S TIER", "dur": 1.9}]

Verify

python $S/verify_motion.py "<clip>"

Every graphic fires within 0.2s of its cue; no typo'd cue silently dropping a graphic; no overlapping panels; verdicts in ascending order.