CRT Tools Guide - ZFEbHVUE/Batocera-CRT-Script GitHub Wiki

📺 CRT Tools Guide

This guide covers the built-in CRT Tools available from the Main Menu in EmulationStation when using the Batocera CRT script.

📚 Table of Contents (click to expand)

🧭 CRT Tools in EmulationStation

Main Menu View

Tools Overview

🛠️ Tool Overview

1. CRT Grid Tool

The Grid Tool helps you adjust the image geometry using your CRT's service menu.
It overlays a reference grid which is ideal for aligning the screen properly before making any software-based adjustments.

➡️ A visual comparison of the grid before and after proper adjustment can be seen in
Grid Comparison under CRT Geometry Adjustments.

2. CRT Geometry Adjustments

This tool adjusts CRT geometry system-wide in software.
It is primarily used when your CRT’s image is off-center and the built-in monitor profiles do not match your display well.

  • Create a custom monitor profile
  • Use a keyboard or gamepad to move the image onscreen
  • Follow the instructions to center the grid

🖼️ Grid Comparison (Before and After)

This tool also uses the same 640x480 grid overlay as the CRT Grid Tool.
Your goal is to push the red border into the overscan area of your CRT.

🔹 Before adjustment (default grid):
This is what it may look like before alignment:

✅ After adjustment (ideal):
This is how it should look once properly adjusted:

📝 Proper adjustment is all about achieving balanced overscan.

You want the outer red border of the grid to be just outside the visible area of your CRT — but not too far.

This ensures:

  • Console games (which were designed with overscan in mind) display correctly
  • Arcade games (which often had zero overscan) aren't overly cropped

The ideal position is when the entire red outer border is hidden off-screen, while the first white grid lines are fully visible. You should also still see roughly half of the red lines just before them — both horizontal and vertical. This gives you a precise overscan margin, ensuring proper alignment without losing meaningful content.

📺 What is overscan?
Overscan is the area outside the visible screen on a CRT. Most consoles were designed with it in mind — they used a buffer zone around the image that wouldn't be seen. This is why you're expected to lose a small part of the edges on a CRT.

However, arcade cabinets were typically manually adjusted per game. The monitor would be dialed in precisely for that game’s resolution and layout.

⚖️ In short:
You don’t want too little overscan (some games may look cramped or broken), but also not too much (important content like health bars might get cut off). Aim for the red border to hug the edge of the visible screen — close to the first red dots on the grid.

ℹ️ If you’ve already aligned things well using the CRT Grid Tool (#1), you likely won’t need to use this tool.

⚠️ Note: This tool cannot adjust vertical size — that must be done via the CRT service menu.

📌 After using this tool, you should continue with Tool #3: ES Centering & Scaling to finish the process.

3. ES Centering & Scaling Tool

Use this tool to fine-tune scaling and centering in EmulationStation.
It's helpful when:

  • The CRT service menu and Grid Tool (#1) can't get it perfect
  • CRT Geometry Adjustments (#2) still leave the image slightly off

🎯 You can also get a visual explanation of how each value affects the screen by referring to the dedicated reference page:
🔗 EmulationStation Scaling and Centering – Value Guide

⚠️ Important Notes About Geometry

Always Follow This Order:

  1. Use the CRT Grid Tool to align your image using the CRT's service menu
  2. Only then, if needed, use the Geometry Adjustments tool
  3. Finalize with ES Centering & Scaling if EmulationStation is slightly off

Why This Matters:

  • Always adjust geometry in 640x480@60Hz (recommended) or 320x240@60Hz (Not recommended) first.
  • Make sure to note your CRT’s original service menu values before changing anything.
    • Save them on your phone
    • Write them down on paper
    • Tape it to the back of your TV
  • These values are essential in case you need to reset or recover.

🎯 Preserve CRT Range for In-Game Adjustments

If you over-correct using software-based geometry adjustments, you'll lose valuable CRT range.

This is critical because:

  • Tools like GroovyMAME, RetroArch, and SwitchRes rely on that range
  • Geometry corrections should be minimal in software
  • Proper initial setup via the service menu gives you more room to work with in-game resolutions and videomodes.conf

📝 Bottom line:
Do the heavy lifting in the service menu using the grid overlay. Only then use software tools for minor tweaks.

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