Codex Video Generation: One High-Res Image Per Scene, Not a Cropped Grid

Melvin Vivas · X video post · 2026-09-22 · 0:13 · 1,183 views · Open on X

Topics: AI Dev Tools & Productivity, Prompt & Context Engineering · Level: beginner

Summary

This is a 13-second X post with no speech. Melvin Vivas reflects on a video he made with OpenAI's Codex. Codex made one grid image and cut each scene out of it, so every scene came out low-resolution. His lesson is to make one high-res image per scene, and to put that in your instructions instead of trusting the agent (he names "Astra ultra") to work it out.

Key points

• When an AI coding agent like Codex builds a multi-scene video, cutting scenes out of one grid image makes each scene low-resolution.
• Better: generate a separate high-res image for each scene.
• Even a strong model or setting (the creator names 'Astra ultra') may not choose the better approach by itself. State the image-generation strategy in your prompt.
• The creator plans to rework the video once his usage limits reset, so expect to iterate on agent output.

Resources mentioned

• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more
• Astra ultra · tool · openai.com · free
  The AI assistant or model ("Ultra" tier or mode) the creator prompted to build the interface. The post doesn't say exactly what it is.
  Also in: Read the GPT-6 Astra launch article to learn what the model can do (Melvin Vivas on X · notes), OpenAI Agents API with Bring Your Own Sandbox as a backend for a 'software factory' (Melvin Vivas on X · notes), Demo: AI Coding Agent Generates a "Software Factory" UI (Frontend Only) (Melvin Vivas on X · notes)

Try this

• When you ask an agent to make multi-scene visuals, tell it to generate one high-res image per scene instead of cropping scenes from a grid.
• Have Codex build a short multi-scene video, with one high-res image generated for each scene.