video-core

Video core

The engine under the video library. A project is a folder with a video.json (the plan); scripts check it, set scene lengths from the voice, turn it into a film (assets/film/resolve.mjs), render the picture with Remotion (assets/remotion/), then mix the voice, a music bed and sound effects with ffmpeg. You edit video.json; the code draws the frames, so the same file gives the same video. <skill> below is the folder that holds this SKILL.md.

Use when

• The user has or wants a video.json and asks to check, render, re-render or credit it.
• Another video skill hands over a project folder to render.
• The Remotion engine needs setting up (engine.mjs).

Don't use when

• The user wants the script, the voice, a diagram's data or a screen capture. Those are separate skills; do not draw frames by hand.
• The engine or FFmpeg is missing and the user has not set them up. Run engine.mjs status and /video doctor; never install anything yourself.

Steps

1. Engine: node <skill>/scripts/engine.mjs status. Not ready: node <skill>/scripts/engine.mjs setup writes the pinned package.json to ~/.aisle-video/remotion and prints the two commands for the user to run there. Say the Remotion licence line it prints.
2. Write or edit <project>/video.json (references/video-json.md; kinds and props in references/scene-kinds.md; schema in <skill>/assets/video.schema.json). Look settings live in style (preset, captions, music).
3. Run node <skill>/scripts/build.mjs <project> --draft (check, timing and render in one call; no flag for the final, which also writes credits). It stops at the first step that fails and shows its message: fix it and run again. The steps by hand: check.mjs, timing.mjs (after the voice), render.mjs [--draft] [--preset name].
4. Look at the draft: node <skill>/scripts/review.mjs stills <project> --at 0.5,3,7 (one time per scene), once. When it is accepted, node <skill>/scripts/review.mjs approve <project>; the final refuses to run if the project changed since, unless --ignore-approval. Every render writes out/<name>.validation.json; fix a failed one.
5. The final writes out/<name>.mp4, out/<name>.srt and .vtt (when there are captions), and credits.mjs writes credits.json and CREDITS.txt; it fails if an asset has no licence.

Budget

• Search first (grep, glob, symbol search). Read line ranges, not whole files.

• Read at most 8 files per step. If you need more, write down what you learned and narrow the question.

• Do not re-read a file you just wrote or edited.

• Prefer the smallest command output that answers the question: head, tail, quiet flags, filtered lists.

• Run each script once per change. Do not read out/rm/ or timing.json to check them; the scripts print what matters.

• Render a draft before the final, and re-render only after check.mjs passes. A draft renders at half size, so it is about 4 times faster.

Output

• The path of the MP4, its length and size, the subtitle files and the credits files.
• The disclosure advice from credits.mjs, in its words, and any note: lines render printed.

Done when

• check.mjs exits 0, render.mjs printed the output path, and credits.mjs exited 0.
• No asset lacks a licence and nothing was installed or fetched by the scripts.