Sub2Learn Skill — let your AI agent handle movie subtitles

English · 中文

Security checks and private reporting: SECURITY.md. CI scans the complete Git history and current files for secrets. Local regressions: node tools/test-local.mjs.

An agent skill for Claude Code, Codex and other AI agents: they open sub2learn.com in a headless browser and use it to extract, merge and translate subtitles for you — including Blu-ray image subtitles (OCR) and translations that only cover the lines above your English level. It runs fine on a Linux VPS with no display. The video itself never leaves your machine.

What you can ask for

Say to your agent	What happens
"Merge the English and Chinese subtitles of movie.mkv into one file"	merge → one bilingual SRT, English on top, Chinese below, aligned on the English timing
"Put the Chinese line on top"	merge --top chi --bottom eng
"Get the subtitles out of movie.mkv"	extract → every text subtitle track as .srt
"The Chinese track is image subtitles, turn it into text"	extract --track N → local OCR of Blu-ray PGS
"Make a CET-4 study subtitle from movie.en.srt"	translate --level cet4 → only lines above CET-4 get a Chinese line, the rest stays English for practice
"Translate every line into Traditional Chinese"	translate --level all --to zh-Hant
"Merge these two SRT files"	merge-srt (local, no browser)

Example prompts:

• "Use the sub2learn skill to merge the English and Simplified Chinese tracks of ~/videos/Arrival.mkv."
• "I'm at CET-6 level. Make me a bilingual subtitle from ~/subs/show.s01e01.en.srt that only translates what I probably don't know."
• "List the subtitle tracks of movie.mkv, OCR the PGS English track and merge it with the Chinese one."

Install

Claude Code

Plugin marketplace (inside Claude Code):

/plugin marketplace add jwsky/sub2learn-skill
/plugin install sub2learn@sub2learn-skill

Or with the installer (also runs the setup below):

curl -fsSL https://raw.githubusercontent.com/jwsky/sub2learn-skill/main/install.sh | bash -s -- --claude

Prefer to read the script first? Clone, then run it from the checkout:

git clone https://github.com/jwsky/sub2learn-skill
bash sub2learn-skill/install.sh --claude      # or --codex, or both

Codex

Ask Codex — its built-in skill installer handles it:

Install the skill from https://github.com/jwsky/sub2learn-skill/tree/main/skills/sub2learn

Or: curl -fsSL https://raw.githubusercontent.com/jwsky/sub2learn-skill/main/install.sh | bash -s -- --codex

Any other agent

git clone --depth 1 https://github.com/jwsky/sub2learn-skill.git
cd sub2learn-skill/skills/sub2learn && bash scripts/setup.sh

Then tell the agent: "Read sub2learn-skill/skills/sub2learn/SKILL.md and follow it."

The skill checks itself on first use (doctor) and runs scripts/setup.sh when the browser or the npm package is missing, so a plugin or skill-installer install needs no extra step.

Requirements

Node.js	20 or newer (Playwright 1.63 requires it)
Browser	Playwright's Chromium (default; x86_64 and ARM64) or Google Chrome / Edge / distro Chromium
OS	Linux, servers included (tested: Ubuntu 24.04 on ARM64, and Ubuntu 24.04 x86_64 in CI). Headless — no display needed; running as root is fine. macOS should work the same way but is not tested.
Memory	~400 MB for extract/merge/translate, ~550 MB+ with OCR (measured on the bundled samples); plan 1 GB, 2 GB for OCR
Disk	~650 MB for Playwright's Chromium (~270 MB with --shell-only)
Network	access to https://sub2learn.com

Linux VPS notes:

• Debian / Ubuntu — bash scripts/setup.sh as root (or with sudo) installs Chromium and its system libraries.
• RHEL / Alma / Rocky / CentOS Stream — easiest is Google Chrome's RPM (it pulls every dependency), then use --browser chrome: sudo dnf install -y https://dl.google.com/linux/direct/google-chrome-stable_current_x86_64.rpm && bash scripts/setup.sh --browser none
• ARM64 (Ampere, Graviton…) — use the default Playwright Chromium; the skill is developed on an ARM64 Ubuntu VPS.
• Already have Chrome running with --remote-debugging-port? Use --cdp http://127.0.0.1:9222.

More: skills/sub2learn/references/vps-setup.md

How it works

 your agent ──► node scripts/s2l.mjs merge movie.mkv
                     │  Playwright starts headless Chromium / Chrome
                     ▼
              https://sub2learn.com  (the ordinary public page)
                     │
   MKV/WebM ─────────┤ the page's Web Worker streams the file from your disk
   (stays local)     │ (File API), keeps only subtitle packets, OCRs PGS images
                     │ with Tesseract (WASM) → track list · SRT · bilingual merge
                     │
   subtitle text ────┤ "translate" uploads the SRT text; the site marks lines above
   (translate only)  │ your level and translates just those (Bing, Google fallback)
                     ▼
              downloads saved next to your file (or --out)

Because the agent uses the same page a person would, results match the website exactly, and no ffmpeg/Tesseract installation is needed.

Commands

Run from the skill folder (skills/sub2learn). Every command prints one JSON object (progress goes to stderr).

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