Avideo scaler is a system that convertsvideo signals from onedisplay resolution to another; typically, scalers are used to convert a signal from a lower resolution (such as480pstandard definition) to a higher resolution (such as1080ihigh definition), a process known as "upconversion" or "upscaling" (by contrast, converting from high to low resolution is known as "downconversion" or "downscaling").
Video scalers are typically found insideconsumer electronics devices such astelevisions,video game consoles, andDVD orBlu-ray players, but can also be found in other AV equipment (such asvideo editing andtelevision broadcasting equipment). Video scalers can also be completely separate devices, often providing simplevideo switching capabilities. These units are commonly found as part ofhome theatre or projected presentation systems. They are often combined with othervideo processing devices or algorithms to create a video processor thatimproves the apparent definition of video signals.
Video scalers are primarily adigital device; however, they can be combined with ananalog-to-digital converter (ADC, or digitizer) and adigital-to-analog converter (DAC) to supportanalog inputs and outputs.
Thenative resolution of a display is how many physical pixels make up each row and column of the visible area on the display's output surface.[1] There are many different video signals in use which are not the same resolution (neither are all of the displays), thus some form of resolution adaptation is required to properly frame a video signal to a display device. For example, within theUnited States, there areNTSC,ATSC, andVESA video standards, each with several different resolution video formats. Multiple common resolutions are also used forhigh-definition television;720p,1080i, and1080p.
While scaling a video signal does allow it to match the size of a particular display, the process can result in an increased number ofvisual artifacts in the signal, such asringing andposterization.[citation needed]
Television channels that air a mixture of16:9high-definition programming and4:3 standard definition programming may employ scaling or cropping in order to make the programming fill the entire screen, as opposed topillarboxing the feed instead, in order to maintain consistency in format.[2][3] Likewise, broadcasters downscale programming produced in 16:9 for broadcast on their 4:3 feeds throughletterboxing—either as a full 16:9 letterbox, or a partial14:9 letterbox—a technique used primarily by European broadcasters during the transition todigital terrestrial television.[4][5] TheActive Format Description standard is a system of variables defining various scaling, letterboxing, and pillarboxing states; broadcasting equipment and televisions can be configured to automatically switch to the appropriate state based on the AFD flag encoded in the content and the aspect ratio of the display.[6]
When the U.S. cable networkTNT introduced an HD feed in2004, it controversially employed a stretching system known as FlexView (which was also offered to other broadcasters). FlexView used anonlinear method to stretch more near the edges of the screen than in the center of it. The practice was imposed by the senior vice president ofbroadcast engineering at TNT, Clyde D. Smith, who argued that pillarboxing led to inconsistency between programs for viewers, could causeburn-in onplasma televisions, some older HDTVs could not stretch 4:3 content automatically, and the quality of stretching on some displays was poor.[2] Despite TNT's intentions, the system was frequently criticized by viewers of high definition channels, with some nicknaming the effect "Stretch-O-Vision".[2][7]
In 2014,FXX faced similar criticism for its use of cropping and scaling on reruns ofThe Simpsons (which only started producing episodes in HD beginning in its 20th season), as its cropping method caused variousvisual gags to be lost. In February 2015, FXX announced that in response to these complaints, it would present these episodes in their original 4:3 aspect ratio on its video-on-demand service.[3][8]
Some series that were originally shot on35 mm film—such asFriends andSeinfeld—have been converted to high-definition by cropping a widescreen image from the4-perf pulldown.[9][10][11]
In 2023, video upscaling products usinggenerative artificial intelligence were previewed or released, such as NVIDIA'sVideo Super Resolution andAdobe's Project Res-Up. Unlike previous upscaling systems, these technologies generated new data based on provided video frames.[12][13][14]