A flicker fixer or scan doubler is a piece of

computer hardware Computer hardware includes the physical parts of a computer, such as the computer case, case, central processing unit (CPU), Random-access memory, random access memory (RAM), Computer monitor, monitor, Computer mouse, mouse, Computer keyboard, ...

that de-interlaces an output video signal. The flicker fixer accomplishes this by adjusting the timing of the natively interlaced

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

to suit the needs of a progressive display Ex: CRT computer monitor. Flicker fixers in essence create a progressive frame of video from two interlaced fields of video. Flicker fixers

sample Sample or samples may refer to: Base meaning * Sample (statistics), a subset of a population – complete data set * Sample (signal), a digital discrete sample of a continuous analog signal * Sample (material), a specimen or small quantity of s ...

the NTSC/PAL output from the output device and store each scan line from the field currently being displayed in

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...

while simultaneously outputting the line alternately with the corresponding neighboring lines from the field stored previously (''

weaving Weaving is a method of textile production in which two distinct sets of yarns or threads are interlaced at right angles to form a fabric or cloth. Other methods are knitting, crocheting, felting, and braiding or plaiting. The longitudinal th ...

''). Some more advanced flicker fixers integrated in add-on graphics cards use more sophisticated methods. Outputting the image at double scan rate essentially composes a progressive display with all lines from both fields at full vertical refresh rate. This promotes the horizontal

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of the signal from 15.734 kHz to 31.47 kHz (in the NTSC case, numbers for PAL are slightly lower), which can be the used to drive a

VGA Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the PC industry within three years. The term can no ...

monitor from an output device.

Use with the Amiga

One computer capable of producing an interlaced image is the

Amiga Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...

. The Amiga's default video mode is

PAL Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...

. NTSC and PAL interlaced screens have two fields called odd and even. The fields switch every 60th of a

second The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...

on NTSC, or 50th of a second on PAL, which allows for higher resolution while using a narrower signal

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

than full 50 or 60

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progressive video would require, but it can also produce an alarming

jitter In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. Jitter is a significa ...

ing effect for graphics with high contrast details between fields. This NTSC/PAL compatibility gave the Amiga a distinct edge in uses such as television production and

gaming Gaming may refer to: Games and sports The act of playing games, as in: * Legalized gambling, playing games of chance for money, often referred to in law as "gaming" * Playing a role-playing game, in which players assume fictional roles * Playin ...

, but since the original Amigas were unable to produce vertically high-resolution displays without flickering this was unsuitable for office-like usage where one might need to work with a clear high-resolution image for several hours. Flicker fixers were devised to remedy this. The later iteration of the Amiga - the Amiga 3000 had a custom chip called

Amber Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In Ma ...

which could perform flicker-fixing on any signal. The ECS and

AGA Aga or AGA may refer to: Business * Architectural Glass and Aluminum (AGA), a glazing contractor, established in 1970 * AGA (automobile), ''Autogen Gasaccumulator AG'', 1920s German car company *AGA AB, ''Aktiebolaget Svenska Gasaccumulator'', a ...

chipset In a computer system, a chipset is a set of electronic components An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are ...

could also output VGA display modes. Commodore offered the A2320 Display Enhancer Board for this purpos

The board fit neatly in a video graphics adapter slot on the A2000 series computer. It supported the new video modes offered by the

Enhanced Chip Set The Enhanced Chip Set (ECS) is the second generation of the Amiga computer's chipset, offering minor improvements over the original chipset (OCS) design. ECS was introduced in 1990 with the launch of the Amiga 3000. Amigas produced from 1990 o ...

(ECS) and

AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early version ...

2.0, including the Productivity Mode. Also, the earlier A2024 'Hedley' greyscale monitor featured an integrated flicker fixer, supporting up to 8 shades of grey. {{DEFAULTSORT:Flicker Fixer Amiga Computing output devices