music-to-video

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name: music-to-video
description: "Turn a music track (an audio file, a video to pull audio from, or a track generated from a mood brief) into a beat-synced video — lyric video, slideshow, or kinetic promo. The music drives all pacing; any user-supplied images/videos are cut onto the same beat grid, and a complete video needs zero assets. Narrated pieces → the input-matched workflow (see /hyperframes). Unclear → /hyperframes."
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> **First, keep this skill fresh — confirm with the user before running:** `npx hyperframes skills update music-to-video`. 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.

# music-to-video — one music-grounded, beat-synced video workflow

Use this skill to turn a **music track** into a beat-synced HyperFrames video. You analyze the track once, lay out the frames, fill in a per-frame plan, and build each frame as a composition. The input is a music track plus optional user images or videos — there is **no narration and no website capture**. Typography and templates are the floor (a complete video needs zero assets); any media the user supplies is cut in on the same beat grid.

You are the **orchestrator**. Work in `videos/<project>/`. Run the steps in order and pass each **Gate** before moving on. Two steps need the user: **Step 3** (plan approval) and **Step 6** (render approval) — both are checkpoint gates per `../hyperframes/references/brief-contract.md` (read it before Step 0): in autonomous mode, post the summary as a heads-up and proceed instead of waiting. Do every step yourself except **Step 4**, where you dispatch **one sub-agent per frame**. Keep design and motion rules out of this file — they live in `references/` and the `frame-worker` sub-agent.

`SKILL_DIR` = this skill directory. `PROJECT_DIR` = `videos/<project-name>/`.

Workflow: Step 0 setup → `hyperframes.json` + `assets/bgm.mp3`; Step 1 analyze → `audiomap.json`; Step 2 skeleton → `STORYBOARD.md` (frames, groups `TBD`); Step 3 plan → complete `STORYBOARD.md` + `frame.md`; Step 4 build → `compositions/frames/NN-*.html`; Step 5 assemble → `index.html`; Step 6 render → `renders/video.mp4`.

## Two ideas that shape everything

- **One analyzer, and you trust it.** `analyze-beatgrid.py` is the only beat analyzer — never re-measure beats with another tool or by ear. Its energy / density / rolls / onsets / silences are always reliable. Its `bpm` and `beats_sec` are reliable **only when the music is genuinely rhythmic**; on calm music the grid is a metronome the tracker imposed, so pace by phrases and energy instead and never hard-cut to it. Deciding which case you're in is each frame's `pacing` (Step 2).
- **One frame = one file; groups live inside.** Step 2 cuts the track into **frames**, and each frame becomes one composition file `compositions/frames/NN-<frame_id>.html`, built by one frame-worker. A frame can subdivide into **groups** (each a template or a motion-primitives combo). Extra density goes _inside_ a group, so **frame count tracks distinct treatments, not beats** — a fast track does not blow up the number of sub-agents.

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## Step 0: Setup, BGM, and inputs

Goal: Establish the music source, create the HyperFrames project, and note any user-supplied media.

**The brief starts at the intent layer.** Opening rule, in order: **(1)** `BRIEF.md` exists → read it and ask nothing it answers — its `flow`/`storyboard` derive the mode (brief contract § 1). **(2)** No `BRIEF.md` but the project exists → resume from what's on disk; never re-interrogate. **(3)** A fresh creation request that arrived here directly → read `/hyperframes` and run its intent layer (`references/intent-interview.md`): it confirms this route's must-haves (the music source, destination → aspect — `../hyperframes/references/routes/music-to-video.md`) and announces what stays deferred — brand and genre are chosen at Step 3 by design. Write `BRIEF.md` immediately aft