A video scaler is an algorithmic processing device for converting video signals between one arbitrary resolution/aspect-ratio and another resolution/aspect-ratio. In their most common application they are "upscaling" or "upconverting", taking a low resolution (Standard Definition) video and increasing the resolution to a high resolution (High Definition) video. This does not necessarily mean that the picture becomes clearer/more detailed - as scalers in their simplest form only increase the sample points for the original signal resulting in more data points for the original given information. Better scaling devices include other signal conditioning to maintain the original signal details when increasing the resolution. This also does not mean that placing a video scaler before a limited-capability display device will 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). Confusion is caused within the general public, due to how little is understood about video scalers and where they are used. Manufacturers of digital displays (DLP, LCD, LCOS or “SXRD”, Plasma) don’t tell customers that there is a simple video scaler built into their display which accepts a video signal and converts it to what the display is expecting.
These devices are primarily digital, however – a video scaler 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.
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. Since not every video signal in use in the world is exactly the same resolution (and neither are all of the displays), some form of resolution change (video scaling) is required. For example, within the United States, there are NTSC, ATSC, and VESA video standards each with several video formats. The most common example of a video scaler implementation is within a standard desktop monitor, which converts a VGA (640x480 pixels) signal from a computer 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 pixel on the TFT glass; in this case the resolution outputted by the computer would only use approximately 25% of the actual pixels without a scaler. By upscaling the computer’s output to the native resolution of the TFT glass, the image fills the whole screen without any black pixels surrounding the active image content.
Upscaling DVD
Upscaling DVD (Digital Versatile Disc) Players are a reasonably cheap way of upscaling standard DVD-Video discs using a video scaler to match the pixel count of the signal to the physical, or native, pixel count on a high-definition television or computer monitor, resulting in better detail and color consistency. Standalone DVD players which feature upscaling use either a standard component video, VGA analog cable, DVI-D or HDMI digital cable to connect to the high-definition television. Standalone DVD players with component video or VGA output connectors use a digital-to-analog integrated circuit microchip which does the upscaling, while DVD players with DVI-D or HDMI output connectors use a digital-to-digital integrated circuit microchip which does the upscaling. Computer software DVD-Video players like PowerDVD and WinDVD also features upscaling of DVD-Video.
It is important to note, as mentioned above, that most flat panel televisions internally employ upscaling filters to scale various input resolutions to their target resolutions, i.e an upscaling DVD player is not required to watch DVD video (standard definition) on a high definition flat panel TV.
Further, TVs employ some kind of overscan correction and often upscale images by around four percent and weed out the edges of incoming video, primarily due to historical reasons (some televisions have options not to do this, often called dot to dot or 1:1 mode). As a result, upscaling DVD players that change the output from the native 480 line ouptut of DVDs result in two scaling operations being used to display the final image (instead of the single operation within the TV itself). This often negates the advantages of scaling from within the DVD player, which for technical reasons can be superior to the TVs internal scaler. The DVD player has access to MPEG metadata for each frame of video (interlaced/progressive, motion vectors, etc.) which allow a better deinterlacer and chroma upsampler (these steps are part of the scaling process) than the TV which no longer receives this information.
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 or functions may include Deinterlacing, Aspect Ratio Control, Zoom and Pan, Brightness/Contrast/Hue/Saturation/Sharpness/Gamma adjustments, Frame Rate Conversion, Color Point Conversion (601 to 709 or 709 to 601), Color Space Conversion (Component to RGB or RGB to Component), Mosquito Noise Reduction, Block Noise Reduction, Detail Enhancement, Edge Enhancement, Motion Compensation, Primary and Secondary Color Calibration (including Hue/Saturation/Luminance controls independently for each) and other features that the video processor manufacturer has elected to include. 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), Gennum (with the VXP chipset), Silicon Optix (with the HQV chipset), and 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
External links
- Standalone Video Processors:
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