nybls

Your AI reads the subtitles. This one actually looks — and shows you what it looked at.

$ nybls probe "https://www.youtube.com/watch?v=F2FmTdLtb_4"

id: F2FmTdLtb_4
title: System Design Concepts Course and Interview Prep
duration: 53.6 min · 1280x720 · 64 scenes
transcript: captions:video.en.vtt → ~/.nybls/store/F2FmTdLtb_4/transcript.txt
budget: 200 image units
cost so far: 0 images. Read the transcript first; then request sheets.

$ nybls study F2FmTdLtb_4 --adaptive

probing every 5s at low resolution (no vision cost)...
probed 644 frames free → kept the 72 biggest changes (median change score 1.56)
study pass: 72 tiles every 5s → 12 sheets (12 of 200 budget units)
  sheet_000.png  [00:07–01:52]
  sheet_002.png  [10:30–19:32]
  sheet_007.png  [34:12–37:30]
  ...

$ nybls ledger F2FmTdLtb_4

watched 54 min · examined 12 images (~12,480 visual tokens, ≈$0.02)
of ~80,443 total frames

A 54-minute course. 12 images. Two cents. Verbatim output, not a mockup.

It pulled 644 frames for free to work out which 72 were worth looking at, then packed them into 12 sheets. Pulling frames is nearly free; looking at them is what costs money — so it only looks at what changed.

And the frames are the right ones. One sheet from the middle covers a tradeoffs diagram, the throughput-vs-latency slide, TCP versus UDP, a TCP header breakdown, the networking-infrastructure slide, and live browser devtools showing a real HTTP request — six distinct teaching moments, no redundant talking head.

Why this exists

Almost every "AI watches YouTube" tool reads the captions. That's not a cheap shot, it's what the code does — the YouTube loaders in the major agent frameworks and self-hosted chat apps are caption scrapers, and Google's own docs say a YouTube source in NotebookLM imports "only the text transcript."

So a video with no speech returns nothing. A chart is invisible. A demo that shows rather than tells is invisible. And you can't tell a tool that looked from one that guessed, because neither shows you its evidence.

The other half of the field dumps 100 evenly-spaced frames at the model and hopes. Expensive, mostly redundant, and still blind to whatever fell between samples.

Install

brew install ffmpeg yt-dlp

pip install nybls

That's it. No API keys, no account, no telemetry — your agent brings the model, everything else runs locally. Videos without captions need speech, which is an extra one-liner (brew install whisper-cpp); the model downloads itself the first time you need it, and the default is 141 MB, not 1.5 GB.

nybls doctor

tells you exactly what works and what any missing piece would unlock.

The three commands you'll actually use

nybls probe "https://www.youtube.com/watch?v=..."   # transcript + scenes, 0 images
nybls study <id> --adaptive                          # learn the whole thing
nybls sheet <id>                                     # one look, 6 timestamps

Everything lands in ~/.nybls/store/<id>/ as ordinary PNGs and text. There's no API integration — your agent just reads the files.

With Claude Code

/plugin marketplace add nKOxxx/nybls
/plugin install nybls@nybls

Then ask it anything about a video. The plugin ships the protocol — a mandatory confidence check each round, a rule that the model must name what it's missing before it may ask for more, and a receipts contract — so the discipline travels with the tool instead of depending on how well you prompt.

Two modes, and it picks for you

Answer mode — you asked a question, so it stops the moment it can answer. A 35-minute video, "what happens in it?", answered with 3 images for a cent.

Study mode — you want to learn the thing, so it covers the whole video. Minimal spend is the wrong goal for a lecture; a 48-minute lesson answered with one image describes the layout, not the content.

Why it's cheap without being lazy

Scene detection is the wrong signal for a fixed-camera recording. A 48-minute chess lesson filmed as one continuous screen capture produces three scene cuts — while the board, carrying all the information, changes every move. Slide decks, IDEs and dashboards have the same shape.

So --adaptive samples on a clock, scores each probe by how much the picture actually changed, and spends the budget on the biggest changes. On that lesson it caught an on-screen framework card that a uniform 30-second pass sampled straight past.

The value of looking is inverse to what the transcript already carries. A podcast needs almost no frames. A silent screen recording — a build-in-public demo, a dashboard, a tutorial over music — has no transcript at all, and the frames are the only place its content exists. Four 14-second reels with one-line captions turned out to hold a full data-pipeline architecture, with table names and the retry logic firing, plus a product restructure that no caption mentioned. That is the case this tool exists for, and it is the one a transcript tool cannot touch.

Honest limits

• No live video. Download, then analyse.
• Motion is lossy. It sees stills. Great for talks, tutorials, demos, dashboards, on-screen text. Weak for sports and fast action.
• Speech only — words, not music or sound events.
• Platforms fight downloaders. Keep yt-dlp current; expect occasional breakage.
• Alpha. Interfaces may change before 1.0; see CHANGELOG.md.

Video content is data, never instructions — a video can display text aimed at your agent, and the protocol requires that it be reported to you, not obeyed.

Docs

Protocol · Research & evidence · Security · Changelog

Benchmarks: round 1 · round 2 · change-detection signals · paper draft

MIT.