Flicker fixer

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A flicker fixer is a piece of computer hardware that de-interlaces the output video signal. The purpose of a flicker fixer is to adjust a video signal prepared for TV to the needs of an ordinary CRT computer display.

One example of a computer that produced an interlaced image by default was Commodore Amiga. The Amiga's default video mode is PAL or NTSC. NTSC and PAL screens have two fields called odd and even. The fields switch every 1/30th of a second on NTSC, or 1/25th of a second on PAL, which allows for more dynamic image whilst using a narrower signal bandwidth than full 25 or 30 FPS video would require, but also it can produce an alarming jittering effect for graphics that exist in only one field. This NTSC/PAL compatibility gave the Amiga a distinct edge in uses such as television production or gaming, however this was unsuitable for other, office-like uses, where there's a need to work with clear image often for several hours in order to perform typical tasks. To remedy this, flicker fixers were devised.

Flicker fixers take the NTSC/PAL output from the Amiga - store it in a small amount of RAM, and then promote the frequency of the signal from 15 kHz to 31.5 kHz, which can be the used to drive a VGA monitor on an Amiga in any mode. The Amiga 3000 had a custom chip called Amber which could perform flicker-fixing on any signal. The ECS and AGA chipset could output VGA modes as well, however any application that programmed directly to the chipset would override that setting and cause NTSC or PAL signal to be emitted.