The Complete Handbook of Scan Converters

Chapter 1: Understanding Scan Converters

What is a scan converter?

A scan converter is a device that converts video signals from one scanning standard or format to another, making it possible to connect video sources and displays that would otherwise be electrically and operationally incompatible. At its core, a scan converter accepts video input in one format—say, interlaced broadcast video at 59.94 Hz—and outputs the same visual content in a different format—say, progressive computer display video at 60 Hz. The image you see is the same. The underlying signal structure has been transformed.

This is more complex than it sounds. A video signal is not simply a stream of colors. It is a precisely timed electrical pattern that encodes both visual information and control signals that tell a display monitor how to draw the image. When you connect incompatible devices, the receiving display either rejects the signal, displays a degraded or distorted image, or fails entirely. A scan converter sits between source and display, intercepts the signal, reconstructs the image content, and regenerates the signal in a format the receiving display understands and expects.

To understand why this matters, you need to know that video standards evolved separately across different industries and regions. Broadcast television in North America uses NTSC (National Television System Committee) standard at 59.94 Hz interlaced. European broadcast uses PAL at 50 Hz interlaced. Computer displays typically use progressive (non-interlaced) scanning at 60 Hz or higher. Arcade machines from the 1980s used custom scanning standards tied to