---

name: video-editing description: "Video editing pipeline: cut footage, assemble clips via FFmpeg and Remotion." user-invocable: false agent: python-general-engineer allowed-tools:

• Read
• Write
• Bash
• Grep
• Glob
• Edit
• Task
• Skill routing: category: video-creation triggers:
  • edit video
  • cut footage
  • make vlog
  • screen recording
  • video workflow
  • ffmpeg
  • remotion
  • demo video
  • make a clip
  • assemble clips
  • video editing
  • image to video
  • audio visualization
  • static video
  • mp4 from image
  • music video
  • podcast video
  • video from image
  • combine image audio
  • album art video
  • cover art video
  • video transcript
  • youtube transcript
  • extract transcript
  • download subtitles
  • what does this video say pairs_with:
  • typescript-frontend-engineer
  • research

---

Video Editing Skill

Overview

This skill implements a 6-layer pipeline where AI handles judgment tasks (what to keep, what to cut, highlight selection) and FFmpeg/Remotion handle mechanical execution deterministically.

| Layer | Name | Mechanism | Primary Tool | |-------|------|-----------|-------------| | 1 | CAPTURE | Inventory source footage | Bash + Glob | | 2 | AI STRUCTURE | Transcript to EDL | LLM judgment | | 3 | FFMPEG CUTS | EDL to segment files | FFmpeg (deterministic) | | 4 | REMOTION COMPOSITION | Segments to TSX composition | Remotion + TypeScript | | 5 | AI GENERATION | Fill gaps with generated assets | ElevenLabs / fal.ai (conditional) | | 6 | FINAL POLISH | Human taste layer | Human + NLE |

---

Deep References

| Signal | Load | Content | |---|---|---| | Shell commands for each phase, gate checks | references/phase-commands.md | Full command blocks for Phases 1-6 | | FFmpeg recipes: cutting, concat, proxy, detection | references/ffmpeg-commands.md | Timestamp extraction, batch cutting, audio normalization, scene/silence detection | | Remotion composition scaffold | references/remotion-scaffold.md | TSX composition template, render command, reuse patterns | | Image-to-video pipeline | references/image-to-video.md | Validate, prepare, encode, verify workflow | | FFmpeg filter graphs for visualization | references/ffmpeg-filters.md | Scale/pad, showwaves, showspectrum, overlay, complete filter graphs |

Instructions

Preflight (Run before Phase 1)

Hard requirements (BLOCK if missing): ffmpeg (all phases), node (Remotion / npx). Soft requirements (WARN if missing): remotion (only required for Phase 4).

which ffmpeg >/dev/null 2>&1 || { echo "ERROR: ffmpeg not found. Install: brew install ffmpeg (macOS) | apt install ffmpeg (Linux)"; exit 1; }
which node >/dev/null 2>&1 || { echo "ERROR: node not found. Install: https://nodejs.org or via nvm"; exit 1; }
npx remotion --version >/dev/null 2>&1 || echo "WARNING: remotion CLI not found. Phase 4 unavailable. Install: npm install @remotion/cli"

---

Phase 1: CAPTURE

Goal: Inventory all source footage and confirm files exist on disk before any processing.

Constraint: Source files are read-only. All FFmpeg commands write to new files only. Never overwrite source footage.

Steps: locate source files (find), inspect each with ffprobe, generate proxies for files >10 min (see references/ffmpeg-commands.md -> Proxy Generation), create working directories (segments/, assembled/). Full command block: references/phase-commands.md -> Phase 1.

Gate: Source files confirmed on disk. File list written to source-inventory.txt. Proceed only when gate passes.

---

Phase 2: AI STRUCTURE

Goal: Analyze content and produce a written EDL (cuts.txt) that drives all downstream cutting.

Constraint: cuts.txt is the contract. The EDL file is the only source of truth for downstream phases. Do not hand-edit FFmpeg commands — generate them from the EDL.

Constraint: Before writing the EDL manually, run FFmpeg scene/silence detection. Detection output informs judgment, not replaces it.

Steps: transcribe with whisper/AssemblyAI, run scene/silence detection, apply judgment (what advances narrative, what is filler, target duration), write cuts.txt in EDL format START_TIME,END_TIME,LABEL, review for overlap and total duration. Full command block and EDL format example: references/phase-commands.md -> Phase 2.

Gate: transcript.txt exists. cuts.txt written to disk. Proceed only when both files exist.

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Phase 3: FFMPEG CUTS

Goal: Execute the EDL deterministically — one FFmpeg cut per segment in cuts.txt.

Constraint: Batch-cut from EDL using a loop. Do not create individual FFmpeg commands per cut. This ensures reproducibility and review capability as a list.

Constraint: Always generate concat-list.txt from cuts.txt order, not from shell glob. Shell glob (segments/*.mp4) sorts alphabetically, not by EDL order.

Steps: batch-cut from EDL with while loop (libx264/aac, -avoid_negative_ts make_zero), verify segments, generate concat-list.txt in EDL order, concat with -f concat -safe 0 -c copy. Full command block: references/phase-commands.md -> Phase 3. See also references/ffmpeg-commands.md -> Batch Cutting.

Gate: All segment files exist. assembled/rough-cut.mp4 written to disk. Proceed only when gate passes.

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Phase 4: REMOTION COMPOSITION

Goal: Wrap segments in a Remotion TSX composition for programmatic overlays, titles, or transitions.

When to use: Only when rough-cut.mp4 requires programmatic elements (animated titles, lower thirds, caption tracks, brand overlays). If rough-cut.mp4 is sufficient, skip to Phase 6.

Constraint: Layer 4 requires TypeScript/React. Hand off to typescript-frontend-engineer for TSX work; return to python-general-engineer for Phase 5 onward.

Steps: initialize Remotion (npm create video@latest first time; otherwise npm install @remotion/cli @remotion/player remotion), scaffold composition (see references/remotion-scaffold.md), render with npx remotion render. Full command block: references/phase-commands.md -> Phase 4.

Gate: assembled/remotion-output.mp4 exists. Proceed only when gate passes.

---

Phase 5: AI GENERATION

Goal: Fill genuine gaps in source material with generated assets — only when needed.

Constraint: Check whether existing footage covers the gap before generating anything. Generate only what doesn't exist.

Decision tree: cut around the gap → update cuts.txt and re-run Phase 3; voiceover → ElevenLabs (authorization required); music → fal.ai (defer to fal-ai-media); b-roll → fal.ai (defer to fal-ai-media). ElevenLabs Python helper, authorization pattern, and save-to-disk flow: references/phase-commands.md -> Phase 5.

Gate: All required generated assets saved to assets/ directory before proceeding.

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Phase 6: FINAL POLISH

Goal: Deliver assembled output and hand off taste-layer work to human.

Constraint: Layer 6 is human territory. The skill assembles; the human finishes. The following require human judgment and should not be attempted programmatically:

• Color grading and color matching between clips
• Music timing and volume ducking
• Caption style, font, positioning
• Transition timing and style
• Final audio mix levels

Handoff template (handoff-notes.txt with source list, EDL, rough-cut path, remaining-for-human checklist): references/phase-commands.md -> Phase 6.

Gate: assembled/rough-cut.mp4 (or assembled/remotion-output.mp4) exists. handoff-notes.txt written to disk.

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Video Transcript Extraction

Pull a video's transcript as readable paragraphs. Prefer uploader subtitles; fall back to auto-generated.

# Path 1: uploader subtitles (accurate)
yt-dlp --skip-download --write-subs --sub-langs en --sub-format vtt -o '<work-dir>/%(id)s' '<URL>'
# Path 2: auto-generated (fallback when path 1 writes no file)
yt-dlp --skip-download --write-auto-subs --sub-langs en --sub-format vtt -o '<work-dir>/%(id)s' '<URL>'
# Clean VTT to paragraphs
python3 skills/research/video-transcript/scripts/vtt_to_paragraph.py <work-dir>/<id>.en.vtt

Options: --timestamps for [mm:ss] markers, --keep-brackets for cue tags, -o FILE for file output. Other languages: change --sub-langs. List available: yt-dlp --list-subs '<URL>'.

Error Handling

| Error | Cause | Solution | |-------|-------|----------| | "No such file or directory" on source | Path in cuts.txt doesn't match filename | Run cat source-inventory.txt. Quote paths with spaces. | | FFmpeg "Invalid option" or codec errors | Codec unavailable or flag syntax error | ffmpeg -codecs \| grep libx264. Fall back to -c:v copy. | | Remotion "Could not find composition" | Composition ID mismatch | Check src/index.ts for registered ID. Match exactly in render command. | | Segments concat in wrong order | Shell glob sorts alphabetically, not by EDL | Generate concat-list.txt from cuts.txt order, not from glob. | | ElevenLabs 401 | ELEVENLABS_API_KEY not set | export ELEVENLABS_API_KEY=your_key before Phase 5. | | No .vtt file from transcript extraction | Video has no subtitles in requested language | yt-dlp --list-subs '<URL>' and pick an available language. |