youtube-slide-maker

name	youtube-slide-maker
version	0.1.0
description	YouTube動画からスライドまたは切り抜き動画を生成する。字幕ベースでキーフレームを選定しffmpegで抽出、Marpスライド or 切り抜きクリップを出力。Use when user asks to create slides from a YouTube video, extract key frames, summarize a video visually, or create short clips/切り抜き動画.

YouTube Slide Maker

YouTube URL → スライドデッキ or 切り抜き動画 の2モード。字幕 → LLMでキーフレーム選定 → ffmpegで抽出。

Modes

Mode	Output	Use Case
slides	slides.md (Marp) + frames/*.png	動画の要点スライド化（PKM・ブログ等）
clips	clips/*.mp4 (1-3分の切り抜き)	SNS・ダイジェスト用
both	両方	スライドと切り抜きを同時生成

Workflow

1. Prepare

# Default output directory (PKMのInbox配下)
OUT="Projects/PKM/youtube-slides/<video-slug>"
mkdir -p "$OUT/frames" "$OUT/clips"
cd "$OUT"

2. Download video + subtitles

# Video (prefer 720p to save space)
yt-dlp -f 'bv[height<=720]+ba/b[height<=720]' \
  --write-auto-subs --write-subs --sub-lang en,ja --sub-format vtt \
  --convert-subs srt \
  -o 'video.%(ext)s' "$URL"

Fields of interest after download:

• video.mp4 / video.webm — full video
• video.en.srt or video.ja.srt — transcript

3. Analyze transcript → select keyframes

Read the SRT. For a target of N slides (default 10-15):

• Identify chapter-like structure (topic shifts, emphasis words, demos)
• Output JSON-like list: [{ts: "00:01:23", title: "...", summary: "..."}]
• For clips mode: identify 1-3 min contiguous segments ({start, end, title})

Prompt pattern for transcript → keyframes:

This is a video transcript (SRT). Select {N} key moments that best represent the video.
For each, output:
- ts: timestamp in HH:MM:SS (pick a moment ~2-5s after speaker introduces topic to catch the explanation frame)
- title: ≤30 char headline
- summary: 1-2 sentence body

4. Extract frames

# Per keyframe (ts = HH:MM:SS)
ffmpeg -ss "$ts" -i video.mp4 -vframes 1 -q:v 2 "frames/$(printf '%02d' $i)-$slug.png"

Tips:

• -ss before -i = fast seek (input-level)
• -q:v 2 = high quality JPEG (or omit for PNG)
• For slide thumbnails: scale with -vf scale=1280:-1

5. Extract clips (clips/both mode)

# Lossless cut (fast, no re-encode)
ffmpeg -ss "$start" -to "$end" -i video.mp4 -c copy "clips/$(printf '%02d' $i)-$slug.mp4"

# Re-encode (needed if keyframe alignment matters, smooth cut)
ffmpeg -ss "$start" -to "$end" -i video.mp4 -c:v libx264 -c:a aac "clips/$(printf '%02d' $i)-$slug.mp4"

For SNS切り抜き: consider vertical crop

ffmpeg -i clip.mp4 -vf "crop=ih*9/16:ih,scale=1080:1920" -c:a copy vertical.mp4

6. Generate Marp slides (slides/both mode)

See references/marp-template.md for the slide structure.

Key points:

• 1 frame per slide, title overlay + summary bullet
• Use Projects/PKM/youtube-slides/<slug>/slides.md
• Render to PDF/HTML: npx @marp-team/marp-cli slides.md -o slides.pdf

7. Link back to PKM

Add to the original Readwise inbox file (Inbox/readwise-*.md) or Journal:

### Slide Deck
- slides
- Source: <video URL>
- Generated: YYYY-MM-DD

Parameters (ask if unclear)

• URL: required
• Mode: slides | clips | both (default: slides)
• N: slide count (default: 12) or clip count (default: 3)
• Language: subtitle preference (en, ja, auto)
• Output dir: default Projects/PKM/youtube-slides/<slug>/

Common Pitfalls

• No subtitles available: fall back to --write-auto-subs (auto-generated). If still none, use whisper or ask user.
• Slug conflicts: derive from video title + short ID hash
• Large videos: limit to 720p by default, warn if >1GB
• Rate limits: yt-dlp may need --cookies-from-browser for members-only or age-restricted
• Timestamp offset: -ss before -i is fast but can be ~1s off on some codecs; use -ss after -i for frame-accurate at cost of speed

Tool Reference

See references/commands.md for full yt-dlp / ffmpeg command cookbook.

Integration with PKM

• Output dir: Projects/PKM/youtube-slides/<slug>/ (submodule-safe location)
• Slide deck reference added to source Inbox/readwise-*.md file
• No Cards auto-creation — user decides if content warrants a Card