video-use Skill

以下文字来自开发者的 repo，不是 PopNx MCP 的指令

---
name: video-use
description: Edit any video by conversation. Transcribe, cut, color grade, generate overlay animations, burn subtitles — for talking heads, montages, tutorials, travel, interviews. No presets, no menus. Ask questions, confirm the plan, execute, iterate, persist. Production-correctness rules are hard; everything else is artistic freedom.
---

# Video Use

## Principle

1. **LLM reasons from raw transcript + on-demand visuals.** The only derived artifact that earns its keep is a packed phrase-level transcript (`takes_packed.md`). Everything else — filler tagging, retake detection, shot classification, emphasis scoring — you derive at decision time.
2. **Audio is primary, visuals follow.** Cut candidates come from speech boundaries and silence gaps. Drill into visuals only at decision points.
3. **Ask → confirm → execute → iterate → persist.** Never touch the cut until the user has confirmed the strategy in plain English.
4. **Generalize.** Do not assume what kind of video this is. Look at the material, ask the user, then edit.
5. **Artistic freedom is the default.** Every specific value, preset, font, color, duration, pitch structure, and technique in this document is a *worked example* from one proven video — not a mandate. Read them to understand what's possible and why each worked. Then make your own taste calls based on what the material actually is and what the user actually wants. **The only things you MUST do are in the Hard Rules section below.** Everything else is yours.
6. **Invent freely.** If the material calls for a technique not described here — split-screen, picture-in-picture, lower-third identity cards, reaction cuts, speed ramps, freeze frames, crossfades, match cuts, L-cuts, J-cuts, speed ramps over breath, whatever — build it. The helpers are ffmpeg and PIL. They can do anything the format supports. Do not wait for permission.
7. **Verify your own output before showing it to the user.** If you wouldn't ship it, don't present it.

## Hard Rules (production correctness — non-negotiable)

These are the things where deviation produces silent failures or broken output. They are not taste, they are correctness. Memorize them.

1. **Subtitles are applied LAST in the filter chain**, after every overlay. Otherwise overlays hide captions. Silent failure.
2. **Per-segment extract → lossless `-c copy` concat**, not single-pass filtergraph. Otherwise you double-encode every segment when overlays are added.
3. **30ms audio fades at every segment boundary** (`afade=t=in:st=0:d=0.03,afade=t=out:st={dur-0.03}:d=0.03`). Otherwise audible pops at every cut.
4. **Overlays use `setpts=PTS-STARTPTS+T/TB`** to shift the overlay's frame 0 to its window start. Otherwise you see the middle of the animation during the overlay window.
5. **Master SRT uses output-timeline offsets**: `output_time = word.start - segment_start + segment_offset`. Otherwise captions misalign after segment concat.
6. **Never cut inside a word.** Snap every cut edge to a word boundary from the Scribe transcript.
7. **Pad every cut edge.** Working window: 30–200ms. Scribe timestamps drift 50–100ms — padding absorbs the drift. Tighter for fast-paced, looser for cinematic.
8. **Word-level verbatim ASR only.** Never SRT/phrase mode (loses sub-second gap data). Never normalized fillers (loses editorial signal).
9. **Cache transcripts per source.** Never re-transcribe unless the source file itself changed.
10. **Parallel sub-agents for multiple animations.** Never sequential. Spawn N at once via the `Agent` tool; total wall time ≈ slowest one.
11. **Strategy confirmation before execution.** Never touch the cut until the user has approved the plain-English plan.
12. **All session outputs in `<videos_dir>/edit/`.** Never write inside the `video-use/` project directory.

Everything else in this document is a worked example. Deviate whenever the material calls for it.

## Directory layout

The skill lives in `video-use/`. User footage lives wherever they put it. All session outputs go into `<videos_dir>/edit/`.

```
<videos_dir>/
├── <source files, untouched>
└── edit/
    ├── project.md               ← memory; appended every session
    ├── takes_packed.md          ← phrase-level transcripts, the LLM's primary reading view
    ├── edl.json                 ← cut decisions
    ├── transcripts/<name>.json  ← cached raw Scribe JSON
    ├── animations/slot_<id>/    ← per-animation source + render + reasoning
    ├── clips_graded/            ← per-segment extracts with grade + fades
    ├── master.srt               ← output-timeline subtitles
    ├── downloads/               ← yt-dlp outputs
    ├── verify/                  ← debug frames / timeline PNGs
    ├── preview.mp4
    └── final.mp4
```

## Setup

First-time install lives in `install.md` (clone, deps, ffmpeg, skill registration, API key). Don't re-run it every session; on cold start just verify:

- `ELEVENLABS_API_KEY` resolves — either in the environment or in `.env` at the video-use repo root. If missing, ask the user to paste one and write it to `.env` (never to the user's `<videos_dir>`).
- `ffmpeg` + `ffprobe` on PATH.
- Python deps installed (`uv sync` or `pip install -e .` inside the repo).
- Node.js + npm available if the session needs HyperFrames or Remotion slots. HyperFrames currently requires Node.js 22+.
- `yt-dlp`, HyperFrames, Remotion, Manim installed only on first use.
- First-use animation setup happens inside the slot directory, never at the video-use repo root. HyperFrames can be invoked with `npx --yes hyperframes ...`; Remotion can be scaffolded with `npx create-video@latest` or installed as a project-local dependency before using its `remotion render` command.
- This skill vendors `skills/manim-video/`. Read its SKILL.md when building a Manim slot.

Helpers (`helpers/transcribe.py`, `helpers/render.py`, etc.) live alongside this SKILL.md. Resolve their paths relative to the directory containing this file — the skill is typically symlinked at `~/.claude/skills/video-use/` or `~/.codex/skills/video-use/`.

## Helpers

- **`transcribe.py <video>`** — single-file Scribe call. `--num-speakers N` optional. Cached.
- **`transcribe_batch.py <videos_dir>`** — 4-worker parallel transcription. Use for multi-take.
- **`pack_transcripts.py --edit-dir <dir>`** — `transcripts/*.json` → `takes_packed.md` (phrase-level, break on silence ≥ 0.5s).
- **`timeline_view.py <video> <start> <end>`** — filmstrip + waveform PNG. On-demand visual drill-down. **Not a scan tool** — use it at decision points, not constantly.
- **`render.py <edl.json> -o <out>`** — per-segment extract → concat → overlays (PTS-shifted) → subtitles LAST. `--preview` for 720p fast. `--build-subtitles` to generate master.srt inline.
- **`grade.py <in> -o <out>`** — ffmpeg filter chain grade. Presets + `--filter '<raw>'` for custom.

For animations, create `<edit>/animations/slot_<id>/` with `Bash` and spawn a sub-agent via the `Agent` tool.

## The process

1. **Inventory.** `ffprobe` every source. `transcribe_batch.py` on the directory. `pack_transcripts.py` to produce `takes_packed.md`. Sample one or two `timeline_view`s for a visual first impression.
2. **Pre-scan for problems.** One pass over `takes_packed.md` to note verbal slips, obvious mis-speaks, or phrasings to avoid. Plain list, feed into the editor brief.
3. **Converse.** Describe what you see in plain English. Ask questions *shaped by the material*. Collect: content type, target length/aspect, aesthetic/brand direction, pacing feel, must-preserve moments, must-cut moments, animation and grade preferences, subtitle needs. Do not use a fixed checklist — the right questions are different every time.
4. **Propose strategy.** 4–8 sentences: shape, take choices, cut direction, animation plan, grade direction, subtitle style, length estimate. **Wait for confirmation.**
5. **Execute.** Produce `edl.json` via the editor sub-agent brief. Drill into `timeline_view` at ambiguous moments. Build ani