Video scaler: Wikis

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A video scaler is a device for converting video signals from one size or resolution 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:

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 an 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, DVI/VGA output from a computer) need to be switched between, while the highest possible resolution is maintained.

Video scalers are primarily a digital device, however they can be combined with an analog-to-digital converter (ADC, or digitizer) and a digital-to-analog converter (DAC) to support analog inputs and outputs. One upscaling process that has gotten a lot of attention is the IMAX DMR.

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Scaling a signal to match the display

The "native 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. 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 States, there are NTSC, ATSC, and VESA video standards each with several different resolution video formats.

This is a comparison of several common video resolutions. The more pixels in an image the greater the possibility for finer detail and fidelity.
A blow-up of a small section of a 1024x768 (VESA XGA) resolution image. The picture is actually made up from very small squares - these are pixels.

Image artifacts/errors related to video scaling

  • Banding or posterization
  • 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; instead, the display will either scale the signal down or possibly crop the signal. A common misconception[citation needed] 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 causes some displays from manufacturers like Pioneer to reduce output brightness to avoid phosphor burn-in from a still image) or to crop off the overscan and zoom the rest.

Upscaling/upconverting DVD

Upscaling/upconverting DVD 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 HDTV, especially one of the fixed pixel display type such as LCD, Plasma display, 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[1] verifying that some upconverting DVD players do produce better video quality. 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 Denon, Pioneer Electronics, Panasonic and OPPO Digital 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, deinterlacing 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, deinterlacing component and video scaler. This type of chip is often called SoC (System-on-a-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 definition of video signals. These other devices may include the ability for:

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 DVD/Blu-Ray Disc players and set-top boxes, to displays like plasmas, DLP (both front and rear projection), LCD (both flat-panels and projectors), and LCOS/”SXRD”. Their chips are also becoming more available in stand alone devices (see "External links" below for links to a few of these).

See also

References

External links

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