A
video scaler is a device for converting
videoVideo is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.-History:...
signals from one size or
resolutionThe display resolution of a digital television or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by all different factors in cathode ray tube and flat panel or projection...
to another: usually "upscaling" or "upconverting" a video signal from a low resolution (e.g. standard definition) to one of higher resolution (e.g. high definition television).
Video scaler devices can be found embedded in:
- Computer monitors
- Televisions
- Video editing
The term video editing can refer to:* non-linear editing system, using computers with video editing software* linear video editing, using videotape* vision mixing, when working with live video signals...
and broadcastingBroadcasting is the distribution of audio and/or video signals which transmit programs to an audience. The audience may be the general public or a relatively large sub-audience, such as children or young adults....
equipment
- Other audio/visual devices
Video scalers can also be a completely separate box, often providing simple video switching capabilities. These units are commonly found as part of home theatre or projected presentation systems. Home theatre uses might include converting a standard definition DVD or video game signal into high-definition for display on a LCD or plasma television while obtaining the best picture quality possible. Scalers can also be found in schools, lecture theatres and modern churches, where numerous video sources (e.g. DVD video, live camera feeds,
DVIThe Digital Visual Interface is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors. It was developed by an industry consortium, the Digital Display Working Group . It is designed for...
/
VGAThe term Video Graphics Array refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987, but through its widespread adoption has also come to mean either an analog computer display standard, the 15-pin D-subminiature VGA connector or the 640×480...
output from a computer) need to be switched between, while the highest possible resolution is maintained.
Video scalers are primarily a
digitalA digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
device, however they can be combined with an
analog-to-digital converterAn analog-to-digital converter is a device which converts continuous signals to discrete digital numbers...
(ADC, or digitizer) and a
digital-to-analog converterIn electronics, a digital-to-analog converter is a device for converting a digital code to an analog signal ....
(DAC) to support analog inputs and outputs. One upscaling process that has gotten a lot of attention is the
IMAXIMAX is a motion picture film format and projection standard created by Canada's IMAX Corporation. The traditional version of IMAX has the capacity to record and display images of far greater size and resolution than conventional film systems...
DMR.
Scaling a signal to match the display
The "
native resolutionThe native resolution of a LCD, LCoS or other flat panel display refers to its single fixed resolution. As an LCD display consists of a fixed raster, it cannot change resolution to match the signal being displayed as a CRT monitor can, meaning that optimal display quality can be reached only when...
" of a display is how many physical pixels make up each row and column of the visible area on the display's output surface. 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 (video scaling) is required to properly frame a video signal to a display device. For example, within the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, there are
NTSCNTSC, named for the National Television System Committee is the analog television system used in most of the Americas, Japan, South Korea, Taiwan, Burma, and some Pacific island nations and territories . is also the name of the U.S. standardization body that developed the broadcast standard...
,
ATSCATSC is a set of standards developed by the Advanced Television Systems Committee for digital television transmission that replaced much of the analog NTSC television system on June 12, 2009 in the United States and will replace NTSC by August 31, 2011 in Canada and December 31, 2021 in Mexico.The...
, and
VESAVESA is an international standards body for computer graphics founded in 1989 by NEC Home Electronics and eight other video display adapter manufacturers....
video standards each with several different resolution video formats.
The most common example of a
video scaler implementation is within a standard
LCD desktop monitorA thin film transistor liquid crystal display is a variant of liquid crystal display which uses thin-film transistor technology to improve image quality . TFT LCD is one type of active matrix LCD, though all LCD-screens are based on TFT active matrix addressing...
, which converts a
VGAThe term Video Graphics Array refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987, but through its widespread adoption has also come to mean either an analog computer display standard, the 15-pin D-subminiature VGA connector or the 640×480...
signal (640x480 pixels) from a
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
into a digital signal with a digitizer and then sends the 640x480 pixels into the
video scaler to be upscaled to SXGA (1280x1024 pixels) for display on a monitor with 1280x1024 physical pixels on the display screen. Without the scaler, the resolution output by the computer would only use approximately 25% of the actual pixels, so the image would not cover the full screen area. By upscaling the computer’s output to the native resolution of the LCD display, the image fills the whole screen without any black pixels surrounding the image content. Usually, the picture is no clearer or more detailed, only larger. The simplest type of scaler does "pixel replication" where a pixel is copied into the next pixel to double the image resolution. Better scaling devices include other processing and filtering techniques to maintain the original details when increasing the resolution.
TVs also typically employ some kind of
overscanOverscan is extra image area around the four edges of a video image that is not normally seen by the viewer. It exists because television sets in the 1930s through 1970s were highly variable in how the video image was framed within the cathode ray tube ....
correction which internally upscales a received image by around four percent (this value varies by manufacturer and display technology) primarily due to historical broadcast reasons (see
Safe areaSafe area is a term used in television production to describe the areas of the television picture that can be seen on television screens.Older televisions can display less of the space outside of the safe area than ones made more recently...
) - this ensures that any artifacts that are a result of the broadcast are not seen by the display customer. Some televisions support an option not to do this, often called "dot-by-dot", "Just" or "1:1" modes. In these modes, a display will attempt to place every pixel it received on the viewable area of the display.
OverscanOverscan is extra image area around the four edges of a video image that is not normally seen by the viewer. It exists because television sets in the 1930s through 1970s were highly variable in how the video image was framed within the cathode ray tube ....
is best described as "zoom", where the top, bottom, and both sides are cut off.
Image Artifacts/Errors Related to Video Scaling
- Banding or posterization
Posterization of an image entails conversion of a continuous gradation of tone to several regions of fewer tones, with abrupt changes from one tone to another. This was originally done with photographic processes to create posters...
- Scaler ringing
- Double scaling - When a source device is used which upscales to a resolution not native to a television's display, the TV can scale the image a second time which unnecessarily reduces the final output quality.
Display Limitations
Placing a video scaler before a limited-capability display device will not remove the limitations of that display device (for instance, you can’t make a 720p display take a 1080p signal and expect to see all 1920x1080 pixels on the 1280x720 display surface). A common misconception of consumers is that if you upscale to 1080p from a 720p source and the TV downscales to 854x480 internally (like within a plasma display), that you would end up with a better image. Since the final display surface does not contain the necessary pixel amount to display the 720p content in its entirety, there is a loss in the vertical and horizontal resolution in the final displayed image. It is preferred to send the display the exact resolution that it needs to output a final display image. Some displays may have a further problem when displaying native resolution however, when sent the exact native resolution image, the display may be programmed to assume that it is receiving a signal from a PC - which will cause it to reduce its output brightness (this is a protection mechanism which display manufacturers like Pioneer have installed to prevent or reduce image
phosphor burn inScreen burn-in, colloquially known as screen burn, is a permanent disfigurement of areas on an electronic display such as a CRT display or computer monitor or television screen caused by cumulative non-uniform usage of the pixels....
).
Upscaling/Upconverting DVD
Upscaling/Upconverting
DVDDVD, also known as Digital Versatile Disc or Digital Video Disc,is an optical disc storage media format, and was founded in 1995. Its main uses are video and data storage...
players contain a scaler, which allows the user to convert lower resolution content into a signal that the display device will handle as high definition content. Depending on the quality of the scaling that is done within the upscaling/upconverting DVD player, the resultant output quality of the video displayed may or may not be improved. The idea behind upconverting DVD players is that when a DVD player is connected to an
HDTVHigh-definition television is a digital television broadcasting system with higher resolution than traditional television systems...
, especially one of the
fixed pixel displayFixed pixel displays are display technologies such as LCD and plasma that use an unfluctuating matrix of pixels with a set number of pixels in each row and column...
type such as
LCDA liquid crystal display is a thin, flat panel used for electronically displaying information such as text, images, and moving pictures...
,
Plasma displayA plasma display panel is a type of flat panel display common to large TV displays . Many tiny cells between two panels of glass hold a mixture of noble gases. The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light...
, or DLP and LCoS projection TV, scaling happens anyway, either inside the player or inside the TV. By performing the scaling closer to the source inside the DVD player, the video scaler gets to work with the original signal without the concern of transmission error or interference. There exist independent benchmark tests verifying that some upconverting DVD players do produce better
video qualityVideo quality is a characteristic of a video passed through a video transmission/processing system, a formal or informal measure of perceived video degradation...
. However, under no circumstances will an upscaling/upconverting DVD player provide "high-definition content", since video information can only be retained or lost in each successive conversion step, but not created. Companies such as
Denonis a Japanese electronics company that originated digital audio technology, while specializing in manufacturing of high-fidelity professional and consumer audio equipment. For many decades, Denon was a brand name of Nippon-Columbia, including the Nippon Columbia record label. In 2001 Denon was...
, Pioneer Electronics,
PanasonicPanasonic is an international brand name for Japanese electric products manufacturer Panasonic Corporation Under this brand the company sells plasma and LCD display panels, DVD recorders and players, Blu-ray Disc players, camcorders, telephones, vacuum cleaners, microwave ovens, shavers,...
and
OPPO DigitalOPPO electronics corp., ltd is an electronics manufacturer based in Dongguan, Guangdong, China. Its American division is OPPO Digital, Inc.OPPO Digital, Inc., is an electronics manufacturer based in Mountain View, California United States...
were among the first to make upconverting DVD players. Now, almost all consumer electronics brands have this product category. Computer software DVD-Video players like PowerDVD and WinDVD tap into a computer's video card in order to upscale a video frame from the DVD content to the user's set output resolution.
A properly-designed upconverting DVD player should have these key parts all with good quality: MPEG decoder,
deinterlacingDeinterlacing is the process of converting interlaced video, like common analog television signals or 1080i format HDTV signal, into a non-interlaced form.- Background :...
component, and video scaler. Among those, the deinterlacing component is the most important one. If the deinterlacer assembles the video frame in an incorrect manner, no matter how good the video scaler is, it still cannot produce the correct video. On the other hand, some upconverting DVD players use a single chip that contains the MPEG decoder,
deinterlacingDeinterlacing is the process of converting interlaced video, like common analog television signals or 1080i format HDTV signal, into a non-interlaced form.- Background :...
component and video scaler. This type of chip is often called SoC (
System-on-a-ChipSystem-on-a-chip or system on chip refers to integrating all components of a computer or other electronic system into a single integrated circuit . It may contain digital, analog, mixed-signal, and often radio-frequency functions – all on one chip...
). Low cost upconverting DVD players usually feature the SoC design.
Video processor
Video scalers are often combined with other video processing devices or algorithms to create a video processor that
improves the apparent definitionImproved-definition television or enhanced-quality television transmitters and receivers exceed the performance requirements of the NTSC standard, while remaining within the general parameters of NTSC emissions standards....
of video signals. These other devices may include the ability for:
- deinterlacing
Deinterlacing is the process of converting interlaced video, like common analog television signals or 1080i format HDTV signal, into a non-interlaced form.- Background :...
- aspect ratio
The aspect ratio of a shape is the ratio of its longer dimension to its shorter dimension. It may be applied to two characteristic dimensions of a three-dimensional shape, such as the ratio of the longest and shortest axis, or for symmetrical objects that are described by just two measurements,...
control
- digital zoom
Digital zoom is a method of decreasing the apparent angle of view of a digital photographic or video image. Digital zoom is accomplished by cropping an image down to a centered area with the same aspect ratio as the original, and usually also interpolating the result back up to the pixel...
and panIn photography, panning refers to the horizontal movement or rotation of a still or video camera, or the scanning of a subject horizontally on video or a display device...
- brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target...
/contrastContrast is the difference in visual properties that makes an object distinguishable from other objects and the background. In visual perception of the real world, contrast is determined by the difference in the color and brightness of the object and other objects within the same field of view...
/hueHue is one of the main properties of a color, defined technically , as “the degree to which a stimulus can be describedas similar to or different from stimuli that are described as red, green, blue, and yellow,”...
/saturationIn colorimetry and color theory, colorfulness, chroma, and saturation are related but distinct concepts referring to the perceived intensity of a specific color. Colorfulness is the difference between a color against gray. Chroma is the difference of a color against the brightness of another color...
/sharpness/gammaGamma correction, gamma nonlinearity, gamma encoding, or often simply gamma, is the name of a nonlinear operation used to code and decode luminance or tristimulus values in video or still image systems...
adjustments
- frame rate
Frame rate, or frame frequency, is the measurement of the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
conversion
- color point conversion (601 to 709 or 709 to 601)
- color space
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components...
conversion (ComponentComponent video is a video signal that has been split into two or more components. In popular use, it refers to a type of analog video information that is transmitted or stored as three separate signals. Component video can be contrasted with composite video in which all the video information is...
to RGBThe RGB color model is an additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors...
or RGB to Component)
- mosquito noise reduction
- block noise reduction
- detail enhancement
- edge enhancement
- motion compensation
Motion compensation is a technique used by video compression. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture may be previous in time or even from the future...
- primary and secondary color calibration (including hue/saturation/luminance controls independently for each)
These can either be in chip form, or as a stand alone unit to be placed between a source device (like a DVD player or set-top-box) and a display with less-capable processing. The most widely recognized video processor companies in the market as of June 2007 are:
- Genesis Microchip (with the FLI chipset)
- Sigma Designs (with the VXP chipset - was Gennum, Sigma Designs purchased the Image Processing group from Gennum on February 8, 2008)
- Integrated Device Technology (with the HQV chipset and Teranex system products - was Silicon Optix, IDT purchased SO on October 21, 2008)
- Anchor Bay (with the VRS chipset and DVDO system products)
All of these companies chips are in devices ranging from DVD upconverting players (for Standard Definition) to
HD DVDHD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisaged to be the successor to the standard DVD format...
/Blu-Ray Disc players and set-top boxes, to displays like plasmas, DLP (both front and rear projection),
LCDA liquid crystal display is a thin, flat panel used for electronically displaying information such as text, images, and moving pictures...
(both
flat-panelsLiquid-crystal display televisions are color television sets that use LCD technology to produce images. LCD televisions are thinner and lighter than CRTs of similar display size, and are available in much larger sizes as well...
and
projectorsAn LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is a modern analog of the slide projector or overhead projector. To display images, LCD projectors typically send light from a Metal halide lamp through a prism that...
), and LCOS/”
SXRDSXRD is Sony's proprietary variant of liquid crystal on silicon, a technology used mainly in projection televisions and video projectors. In the front and rear-projection television market, it competes directly with JVC's D-ILA and Texas Instruments' DLP...
”. Their chips are also becoming more available in stand alone devices (see "External links" below for links to a few of these).
See also
- Display resolution
The display resolution of a digital television or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by all different factors in cathode ray tube and flat panel or projection...
- Deinterlacing
Deinterlacing is the process of converting interlaced video, like common analog television signals or 1080i format HDTV signal, into a non-interlaced form.- Background :...
- Video display standards
- Stretch-o-Vision
Stretch-o-Vision is a neologism used to describe the practice of upconverting video in the 4:3 aspect ratio to the widescreen aspect ratio such as 16:9 in various ways, causing a distorted picture...
- DVD recorder
A DVD recorder , is an optical disc recorder that records video onto blank writeable DVD media...
External links
- Standalone Video Processors: