df-app-walkthrough

Dark Factory — Autonomous App Walkthrough

Overview

Produces a finished walkthrough video of a running web application without a person speaking, clicking, or editing. Everything runs locally: a neural text-to-speech voice, a headless browser, and ffmpeg. No recording SaaS, no upload, no API key — which is what makes it usable on software you are not allowed to screen-share to a third party.

Four stages, each a script:

narration.json ──▶ build-narration ──▶ audio/*.wav + timing.json
                                              │
                                              ▼
                        record-walkthrough ──▶ raw .webm + recorded-timeline.json
                                              │
                                              ▼
                               assemble ──▶ walkthrough.mp4   ──▶ verify

This is a producer skill. Its natural upstream is a written demo script; its natural downstream is df-video-intake (which turns a video back into text) — the two are inverses and are useful in sequence when a recorded walkthrough must become requirements.

When to use

• "Record a walkthrough / demo / product tour of this app."
• A written demo script exists and someone has to perform it, repeatedly, on every release.
• A UI needs a narrated artefact for people who will never be given access to it.
• Regression-by-eye: re-record on each release and compare.

When not to use

• You need a person's own voice and improvisation — record that yourself.
• The thing being demonstrated is non-deterministic and slow (a long generation job). Narrate it over a card instead; see Cards below.

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The load-bearing idea: audio first, video paced to audio

You cannot know how long a sentence takes until it has been spoken. So the narration is synthesized and measured before the browser opens, and the recorder holds each frame until that line has finished.

The recorder then emits the offset each step actually landed at, and assembly places audio and captions at those measured offsets rather than the planned ones. A step that runs long becomes a slightly longer pause instead of desynchronising everything after it.