# Check every render before you trust it (free sample)

A free sample from Video Production with AI Agents by PaperChaseWebb. Written for Claude Code and Codex.

Coding agents will tell you a video is done the moment ffmpeg exits. The builders in our October 2026 research who got good results made the agent look at its own output first. video-use from the Browser Use team checks every cut point before it shows you anything, and the 3D product spot by @0xFizzu caught a vanished liquid and a floating label in test frames, not in the final render. This sample gives you the rule, the skill and the commands.

## The rule

Add this to AGENTS.md or CLAUDE.md:

```text
Before you report any render as done, run the render-checker skill. Never modify anything in sources/. Never upload or post a video without asking me.
```

## The render-checker skill

Save as `.claude/skills/render-checker/SKILL.md` (Claude Code) or `.agents/skills/render-checker/SKILL.md` (Codex).

```markdown
---
name: render-checker
description: Use before reporting any render as done. Checks frames, cuts and audio against the plan.
---
1. Read SHOTLIST.md if it exists, otherwise ask me what the video should show.
2. Probe the file: duration, size, fps, codec. Compare with the plan.
3. Extract frames at the start, middle and end of every shot, and one frame either side of every cut.
4. Look at each frame: text cut off or overlapped, wrong colors, faces cropped, blank or black frames.
5. Measure loudness and true peak, and check each cut for clicks or pops.
6. Check that captions match the spoken words and stay on screen long enough to read.
7. Report every problem with a timestamp and the smallest fix. Say plainly if it is not ready.
```

## Commands it can use

```text
ffprobe -v error -show_entries format=duration:stream=width,height,r_frame_rate,codec_name -of default=nw=1 out/final.mp4
ffmpeg -ss [seconds] -i out/final.mp4 -frames:v 1 out/check/t[seconds].png
ffmpeg -i out/final.mp4 -af loudnorm=print_format=summary -f null -
ffmpeg -i out/final.mp4 -vf "blackdetect=d=0.1:pix_th=0.10" -an -f null -
```

The full pack adds the lane guide (draw in code, edit footage, script 3D, generate), project templates, 16 prompts, three more skills, publishing and privacy checklists, reported render times and 20 video project ideas.