Editing Flicker fixer

{{Short description|Video de-interlacer}}
{{Multiple issues|{{Confusing|date=February 2009}}
{{More citations needed|date=September 2024}}}}

[[File:Flickerfixer.jpg|thumbnail|External flicker fixer]]

A '''flicker fixer'''  or scan doubler is a piece of [[computer hardware]] that [[deinterlacing|de-interlaces]] an output video signal. The flicker fixer accomplishes this by adjusting the timing of the natively [[interlaced video]] signal to suit the needs of a progressive display for example a [[cathode-ray tube|CRT computer monitor]]. Flicker fixers in essence create a progressive frame of video from two interlaced fields of video.<ref>{{Cite web |date=2019-07-24 |title=AE display delay + UI flicker using dedicated GPU - Windows 10 |url=https://community.adobe.com/t5/after-effects-discussions/ae-display-delay-ui-flicker-using-dedicated-gpu-windows-10/td-p/10573170 |access-date=2024-09-11 |website=community.adobe.com |language=en}}</ref>

Flicker fixers [[sampling (signal processing)|sample]] the NTSC/PAL output from the output device and store each scan line from the field currently being displayed in [[Random access memory|RAM]] while simultaneously outputting the line alternately with the corresponding neighboring lines from the field stored previously (''[[Deinterlacing#Field combination deinterlacing|weaving]]''). 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]] of the signal from 15.734&nbsp;kHz to 31.47&nbsp;kHz (in the NTSC case, numbers for PAL are slightly lower), which can be the used to drive a [[Video Graphics Array|VGA]] monitor from an output device.<ref>{{Cite web |title=Flicker Free Plugin : Deflicker Time Lapse, LED and Slow motion / High Frame Rate in HD and 4K :: Digital Anarchy |url=https://digitalanarchy.com/Flicker/main.html |access-date=2024-09-11 |website=digitalanarchy.com}}</ref><ref>{{Cite web |title=How to Fix a Flickering Screen with Intel&reg; Graphics |url=https://www.intel.com/content/www/us/en/support/articles/000026580/graphics.html |access-date=2024-09-11 |website=Intel |language=en}}</ref><ref>{{Cite web |date=2024-05-16 |title=Why is Your Screen Flickering and How to Fix it? |url=https://www.tesmart.com/blogs/news/why-is-your-screen-flickering-and-how-to-fix-it |access-date=2024-09-11 |website=TESmart |language=en}}</ref>

== Use with the Amiga ==

One computer capable of producing an interlaced image is the [[Amiga]].  The Amiga's default video mode is [[PAL]] or [[NTSC]]. NTSC and PAL interlaced screens have two fields called odd and even.  The fields switch every 60th of a [[second]] on NTSC, or 50th of a second on PAL, which allows for higher resolution while using a narrower signal [[Bandwidth (signal processing)|bandwidth]] than full 50 or 60 [[frame rate|FPS]] progressive video would require, but it can also produce an alarming [[jitter]]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 [[computer game|gaming]], 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 [[Amiga custom chips#Amber|Amber]] which could perform flicker-fixing on any signal. The [[Enhanced Chip Set|ECS]] and [[Advanced Graphics Architecture|AGA]] [[chipset]] could also output VGA display modes. Commodore offered the A2320 Display Enhancer Board for this purpose,[https://web.archive.org/web/20110517230430/http://amiga-hardware.com/showhardware.cgi?HARDID=360] The board fit neatly in a video graphics adapter slot on the A2000 series computer. It supported the new video modes offered by the [[Amiga Enhanced Chip Set|Enhanced Chip Set]] (ECS) and [[AmigaOS]] 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.

An alternative is a screen cover. [[Jerry Pournelle]] reported in 1989 that Flicker Master, "a screen that you Velcro over your Amiga monitor ... reduces the flicker from interlace mode something wonderful ... I wouldn't be without it".<ref name="pournelle198902">{{Cite magazine |last=Pournelle |first=Jerry |date=February 1989 |title=Ready Line Overload |url=https://archive.org/details/eu_BYTE-1989-02_OCR/page/n175/mode/2up?view=theater |access-date=2024-10-08 |magazine=BYTE |pages=121-137}}</ref>

==References==
{{reflist}}

{{Amiga hardware}}

{{DEFAULTSORT:Flicker Fixer}}
[[Category:Amiga]]
[[Category:Computer output devices]]