TV and HDTV
1080p 1080p is a high-definition video format with resolution of 1920 x 1080 pixels. The "p" stands for progressive scan, which means that each video frame is transmitted as a whole in a single sweep. The main advantage of 1080p TVs is that they can display all high-definition video formats without downconverting, which sacrifices some picture detail.
1080p TVs display video at 60 frames per second, so this format is often referred to as 1080p60. The video on most high-definition discs (Blu-ray and HD DVD) is encoded at film's native rate of 24 frames per second, or 1080p24. For compatibility with most current 1080p TVs, high-definition players internally convert the 1080p24 video to 1080p60. By late 2007, many HDTVs included the ability to accept a 1080p24 signal directly. These TVs don't actually display video at 24 frames per second because that would cause visible flicker and motion stutter. The TV converts the video to 60 frames per second or whatever its native display rate is. The ideal situation would be to display 1080p24 at a multiple of 24 frames per second, like 72, 96, or 120 frames per second, to avoid the motion judder caused by 3-2 pulldown, which is required when converting 24-frames-per-second material to 60 frames per second.
120Hz refresh rate The digital display technologies (LCD, plasma, DLP, LCoS, etc.) that have replaced picture tubes are progressive scan by nature, displaying 60 video frames per second — often referred to as "60Hz." HDTVs with 120Hz refresh rate employ sophisticated video processing to double the standard rate to 120 frames per second by inserting either additional video frames or black frames. Because each video frame appears for only half the normal amount of time, on-screen motion looks smoother and more fluid, with less smearing. It's especially noticeable viewing fast-action sports and video games. This feature is available on an increasing number of flat-panel LCD TVs.
16:9 See aspect ratio and widescreen.
240Hz refresh rate 240Hz refresh rate reduces LCD motion blur even more than 120Hz refresh rate. 240Hz processing creates and inserts three new video frames for every original frame. Most "240Hz" TVs operate this way, but some models use "pseudo-240Hz" technology which combines 120Hz refresh rate with high-speed backlight scanning. An example of the pseudo-240Hz approach, which can also be very effective, is Toshiba's ClearScan 240™ technology.
3D TV By adding a sense of picture depth and dimensionality, 3D TVs create a more engaging viewing experience that's similar to watching a 3D movie in a theater. Like 3D movies, 3D TV requires that each viewer wear special glasses to see the 3D effects. 3D TV requires the use of wireless "active shutter" glasses.
Whether a 3D TV uses LCD or plasma screen technology, all 3D TVs use a specially-designed screen that can display two different versions of a video image by alternating the video frames at very high speed. 3D video is basically two full-resolution 1080p images, one for your left eye and one for your right. The shutter glasses' lenses darken and lighten rapidly in coordination with the screen's flashing images. The timing of the shutter glasses is wirelessly controlled by an "emitter" that is usually built into the TV. The system creates an immersive viewing experience. True 3D viewing also requires a 3D video source, like a 3D Blu-ray player playing a 3D movie.
For more info, see our intro to 3D, or check out our in-depth 3D TV FAQ.
3-2 pulldown processing Sophisticated video processing common in HDTVs and progressive-scan DVD players. It corrects for artifacts and distortion that occur when film-based material (at 24 frames per second) is converted to video (30 frames per second), then de-interlaced to create a progressive-scan signal. For a more in-depth explanation, see our DVD Player Glossary.
Active shutter glasses To see three-dimensional effects on a 3D TV screen, each viewer must wear a special type of 3D glasses called "shutter" glasses. Also called "active" glasses, these battery-powered liquid-crystal glasses are able to lighten or darken hundreds of times per second to alternately block out the left or right lens in coordination with the video frames flashing on screen. The lenses aren't displaying images, just switching between dark and clear. To anyone not wearing shutter glasses, a 3D TV picture will look blurry. Active glasses are far more technologically advanced than the disposable 3D glasses handed out in movie theaters.
For more info, see our intro to 3D, or check out our in-depth 3D TV FAQ.
ALiS (Alternate Lighting of Surfaces) A type of high-definition plasma TV panel designed for optimum performance when displaying 1080i material. On a typical progressive-scan plasma TV, all pixels can be illuminated at any given instant. With an ALiS plasma panel, alternate rows of pixels are illuminated so that only half the panel's pixels can be illuminated at any moment (somewhat similar to interlaced-scanning on a CRT-type TV). ALiS-based plasmas make up a small part of the overall market; TV makers that use ALiS panels include Hitachi and Fujitsu.
Anamorphic video Refers to widescreen video images that have been "squeezed" to fit a narrower video frame when stored on DVD. These images must be expanded (un-squeezed) by the display device. Most of today's TVs employ a screen with 16:9 aspect ratio, so that anamorphic and other widescreen material can be viewed in its proper proportions. When anamorphic video is displayed on an old-fashioned TV with a 4:3 screen, images appear unnaturally tall and narrow.
Anti-blur technology A technology that reduces image "smearing" or "motion blur" that can sometimes occur with LCD TVs. LCD televisions with anti-blur technology can deliver smoother, cleaner images than those without, particularly during fast-paced scenes. This anti-blur video processing is usually described as 120Hz refresh rate or 240Hz refresh rate. TV makers have their own proprietary names for anti-blur technology; examples include Sony's Motionflow™ and Samsung's Auto Motion Plus.
Artifacts Unwanted visible effects in the picture created by disturbances in the video transmission or processing. Examples include "dot crawl" or "hanging dots" in analog pictures, or "pixelation" in digital pictures.
Aspect ratio The ratio of width to height for an image or screen. The North American NTSC television standard uses the squarish 4:3 (1.33:1) ratio. HDTVs use the wider 16:9 ratio (1.78:1) to better display widescreen material like high-definition broadcasts and DVDs. See our article about aspect ratio to better understand it and get pointers on troubleshooting some common aspect ratio problems.
ATSC (Advanced Television Standards Committee) Formed to establish technical standards for the U.S. digital television system. A TV tuner that can receive local over-the-air digital broadcasts is often called an ATSC tuner.
Audio Return Channel This feature is available on some 2010 TVs and audio/video components with HDMI 1.4 connections. A TV with Audio Return Channel allows a single HDMI cable to send the audio from the TV's built-in tuner "upstream" to a compatible A/V receiver, eliminating the need for a separate optical or coaxial digital audio cable.
Audio/video inputs Using a TV's direct audio/video inputs to connect a DVD player, VCR, camcorder or other video component provides improved picture and sound quality compared to using the everything-on-one-wire RF antenna-style input. If your TV is old enough that it only has RF-type inputs, that's reason enough to consider replacing it, since many newer video components don't include an RF output.
Backlight scanning An anti-blur technology used in some LCD TVs. Typical LCDs use a fluorescent backlight that shines constantly, which can contribute to motion blur. LCD models with backlight scanning have a special type of fluorescent backlight that pulses at very high speed, which has the effect of reducing motion blur. Some recent TVs use backlight scanning along with 120Hz refresh rate for even greater blur reduction.
Big-screen TV See rear-projection TV.
Bitrate Measured as "bits per second," and used to express the rate at which data is transmitted or processed. The higher the bitrate, the more data is processed and, typically, the higher the picture resolution. Digital video formats typically have bitrates measured in megabits-per-second (Mbps). (One megabit equals one million bits.) The maximum bitrate for standard DVDs is 11Mbps; for over-the-air HDTV broadcasts, it's 19.4Mbps. High-definition discs have even higher maximum bitrates: 36Mbps for HD DVD and 54Mbps for Blu-ray Disc™.
Black level Describes the appearance of darker portions of a video image. Black is the absence of light, so to create the black portions of an image, a display must be able to shut off as much light as possible. Displays with good black level capability not only produce deeper blacks, but also reveal more details and shading in dark or shadowy scenes.
Burn-in Screen burn-in can affect TVs that use a phosphor coating on the screen. It was an issue for early plasma TVs. Burn-in can occur when a static image — like a non-widescreen 4:3 image with vertical black bars on the sides, or a scrolling stock or news ticker — remains on-screen for an extended period. These images can become etched into the phosphor coating, leaving faint impressions. In recent years, TV makers have significantly reduced plasma power consumption and refined the panel technology to dramatically reduce the chances of burn-in occurring, while also including the ability to erase burn-in effects. New plasma TVs are nearly immune to screen burn-in. To prevent any possibility of burn-in, plasma owners should follow the manufacturer's guidelines for adjusting the TV's brightness and contrast settings when the TV is new. For tips on TV settings, see our article about optimizing your TV's picture.
CableCARD™ A removable security card available from cable TV providers. It allows a TV with a compatible CableCARD slot to receive digital cable programming, including premium and HD channels, without using a separate set-top box. The FCC (Federal Communications Commission) began requiring service providers to make CableCARDs available as of July 1, 2004. Contact your local cable provider for details regarding the availability and costs of CableCARD-related services. See our article about Cable TV more details about CableCARDs.
Chrominance The color component of a video signal that includes information about hue (shade) and saturation (intensity).
Color resolution (color bit depth) The color resolution of HDTVs and other video gear is typically described as a color bit depth such as "8-bit" or "10-bit." Color resolution indicates how fine the gradations can be between different shades of the same color — it's a measure of color accuracy. Nearly all consumer video equipment is 8-bit, and 8-bit resolution allows 256 possible shades. That's 256 each for the red, green, and blue primary colors. To calculate the total number of possible colors an 8-bit TV can reproduce, you multiply 256 x 256 x 256, which equals 16.7 million. Some TVs use 10-bit panels and video processing. That may not sound like much more, but 10-bit resolution means 1024 possible shades and over one billion total colors.
Color space A "color space" is a defined range of colors, and is usually associated with an industry standard. Examples of color spaces that relate to television and video equipment include NTSC for analog video, and ATSC and x.v.Color for high-definition video. A wider color space offers the potential for deeper hues. Few current HDTVs are even capable of reproducing the full NTSC color space, let alone the wider ATSC color space or the much wider x.v.Color color space. When you see a TV's color range expressed as a percentage of a color space, it's almost always NTSC.
Comb filter A comb filter's task is to remove residual chrominance (color) information from the luminance (brightness) signal. Comb filtering enhances fine detail, cleans up image outlines, and eliminates most extraneous colors from analog video signals. A comb filter is very effective for composite video signals, but is not required and not used for S-video or component video since those connections carry the chrominance and luminance information separately. There are 4 different types of comb filters found in today's TVs, listed here in order of ascending quality:
· Glass: may also be referred to as an "analog" comb filter.
· 2-line Digital: compares consecutive scanning lines within one field of video and makes adjustments to reduce cross-color interference.
· 3-line Digital: compares 3 scanning lines within a field of video. By comparing more picture information, a 3-line filter further reduces color bleeding and dot crawl.
· 3D Digital: not only analyzes consecutive scanning lines within a field, but also analyzes the preceding and following fields. Results in improved color purity and a more stable video image, and nearly eliminates dot crawl and color bleeding. Also called 3D Y/C.
Component video The three-jack component video connection splits the video signal into three parts (one brightness and two color signals). Compared to other analog video connections, component video has increased bandwidth for color information, resulting in a more accurate picture with clearer color reproduction and less bleeding. Component video is the only type of analog video connection that can pass high-definition signals, and provides better picture quality than S-video or composite video connections. See our connections glossary for more info.
Composite video A single video signal that combines brightness and color information. A composite signal is better than an RF signal, but not as good as S-video. A composite video jack is usually a single RCA-type. See our connections glossary for more info.
Contrast ratio Measures the difference between the brightest whites and the darkest blacks that a TV can display. The higher the contrast ratio, the better a TV will be at showing subtle color details, and the better it will look in rooms with more ambient room light. Contrast ratio is one of the most important specs for all TV types.
There are actually two different ways of measuring a TV's contrast ratio. Static contrast ratio measures the difference between the brightest and darkest images a TV can produce simultaneously (sometimes called on-screen contrast ratio). The ratio of the brightest and darkest images a TV can produce over time is called dynamic contrast ratio. Both specs are meaningful, but the dynamic spec is often four or five times higher than the static spec, so make sure you're comparing apples to apples.
CRT (Cathode-Ray Tube) A CRT ("picture tube") is a specialized vacuum tube in which images are created when an electron beam scans back and forth across the back side of a phosphor-coated screen. Each time the beam makes a pass across the screen, it lights up a horizontal line of phosphor dots on the inside of the glass tube. This beam rapidly draws hundreds of these lines from the top to the bottom of the screen, creating the image.
The old-fashioned "direct-view" TVs most people grew up watching have a single large picture tube, while CRT-based rear-projection and front-projection TVs use three CRTs: one each for the red, green, and blue primary colors.
Deep Color A color resolution standard associated with high-definition TVs and video gear that include HDMI 1.3 connections. Deep Color supports 10-bit, 12-bit and 16-bit color bit depths, up from 8-bit, which is the current standard for consumer video. All earlier versions of HDMI supported 8-bit color. (Because video is based on three primary colors, you'll sometimes see Deep Color described as 30-bit, 36-bit and 48-bit.) A higher color bit depth enables finer gradations between different shades of the same color, for smoother gradients and reduced color banding. Deep Color gives TVs the potential to display billions rather than millions of colors, but in order to see that improvement, the entire video production chain has to use it (camera, editing, format, player, display). See color resolution.
De-interlacing The process of converting an interlaced-scan video signal (where each frame is split into two sequential fields) to a progressive-scan signal (where each frame remains whole). De-interlacers are found in HDTVs and progressive-scan DVD players. More advanced de-interlacers include a feature called 3-2 pulldown processing.
Digital audio output A connection found on HDTVs and HDTV tuners for sending the Dolby Digital soundtrack of HDTV broadcasts to an A/V receiver with Dolby Digital decoding. The two most common types of digital output are coaxial and Toslink optical.
D-ILA™ (Direct-drive Image Light Amplification) JVC's proprietary variation of LCoS projection display technology.
Direct-view TV A general term for non-projection types of TVs, which include conventional tube TVs and flat-panel plasma and LCD TVs.
DLNA DLNA, short for Digital Living Network Alliance, is a collaboration among more than 200 companies, including Sony, Panasonic, Samsung, Microsoft, Cisco, Denon and Yamaha. Their goal is to create products that connect to each other across your home network, regardless of manufacturer, so you can easily enjoy your digital and online content in any room.
While all DLNA-compliant devices are essentially guaranteed to work together, they may not be able to share all types of media. For example, a DLNA-certified TV may be able to display digital photos from a DLNA-certified media server, but not videos.
DLP™ (Digital Light Processing) A projection TV technology developed by Texas Instruments, based on their Digital Micromirror Device (DMD) microchip. Each DMD chip has an array of tiny swiveling mirrors which create the image. Depending on the TV's resolution, the number of mirrors can range from several hundred thousand to over two million. DLP technology is used in both front- and rear-projection displays.
There are two basic types of DLP projector. "Single-chip" models, which include virtually all rear-projection DLP TVs, use a single DMD chip, with color provided by a spinning color wheel or colored LEDs. "3-chip" projectors dedicate a chip to each primary color: red, green, and blue. While 3-chip models are considerably more expensive, they completely eliminate the rainbow effect, which is an issue for a small minority of viewers.
Dolby® Digital A discrete multichannel digital audio format that is the official audio standard for HDTV (and DVD). Dolby Digital is normally associated with 5.1-channel surround sound. Though this channel configuration is the most common, it is only one of several possible variations — a Dolby Digital soundtrack can mean anything from 1 to 5.1 channels. To learn about the various surround sound options available, see our article about surround sound formats.
Downconversion All digital TV display technologies have screens with a fixed number of pixels for displaying images. If a video source has a higher resolution than the screen's resolution, the TV will automatically downconvert the video signal to fit the screen. Downconversion reduces image detail, but downconverted pictures can still look very sharp. A good example is a 1080i HDTV broadcast displayed on a 720p TV.
DTV (Digital Television) A general term for the ATSC digital broadcast TV standard, which replaced the NTSC analog broadcast system. DTV comes in two basic flavors: widescreen, high-quality HDTV (High-Definition Television) with Dolby Digital audio, and medium-quality SDTV (Standard-Definition TV).
DVI (Digital Visual Interface) A multi-pin, computer-style connection intended to carry high-resolution video signals from video source components (such as older HD-capable satellite and cable boxes, and upconverting DVD players) to HD-capable TVs with a compatible connector. Most (but not all) DVI connections use HDCP (High-bandwidth Digital Content Protection) encryption to prevent piracy. In consumer electronics products, DVI connectors have been almost completely replaced by HDMI connectors, which carry both video and audio. You can use an adapter to connect a DVI-equipped component to an HDMI-equipped TV, or vice versa, but a DVI connection can never carry audio. See our connections glossary for more info.
Dynamic backlighting Found on many LCD TVs, this feature dynamically adjusts the brightness of the backlight in response to the picture content of whatever you're watching, to improve picture contrast and reduce power consumption. It helps the TV display both bright outdoor scenes and dark indoor scenes with greater accuracy. Use of dynamic backlighting contributes to the very high "dynamic contrast ratio" specs provided by TV makers.
EDTV (Enhanced-Definition Television) A virtually obsolete class of televisions, generally flat-panel LCD or plasma, that displays signals in 480-line progressive-scan (480p) mode. 480p screen resolution is superior to standard analog TV (480i), but not as sharp as true HDTVs (720p or 1080p).
Electronic program guide (EPG) Provides an on-screen listing of available channels and program data for an extended time period (typically 36 hours or more). Examples of program guides include subscription services like TiVo® and free guides like TV Guide® On Screen. To learn more about EPG features and capabilities, see our article about TV Guide On Screen.
Emitter (for 3D TV) An important part of a 3D TV system is the "emitter" that precisely controls the timing of the active shutter glasses. The emitter communicates with the glasses wirelessly via infrared beams. "3D-ready" TVs include a built-in emitter, while "3D-capable" TVs require that you add an outboard emitter box.
For more info, see our intro to 3D, or check out our in-depth 3D TV FAQ.
Energy Star® compliant A certification for consumer electronics products indicating energy efficiency. The Energy Star program was introduced by the EPA (Environmental Protection Agency) in 1992, and set standards for product power consumption in "standby" mode. (When a component is switched off but still plugged into an AC power source, it continues to draw a small amount of power in standby mode to keep circuits active and ready for quick turn-on.) In November 2008, the EPA created the more stringent Energy Star 3.0 specification, which requires energy efficiency when products are in use, as well as when they are in standby mode. Products that meet the new spec are up to 30% more energy efficient than previous models.
For information specifically relating to TV energy use, including our own in-house testing program, see our article on TV Power Consumption.
Ethernet port An Ethernet port on a TV enables a connection to a home network and/or the Internet. What you can do once you're on the network varies by model. Typically, only a select number of websites are accessible, and capabilities may be limited by the speed of your Internet connection.
Field In interlaced-scan video, each complete frame is split into 2 sequential fields, each of which contains half the picture information. One field contains the odd scanning lines, and the other field the even lines.
Flat-panel TV Any ultra-thin, relatively lightweight TV — especially those which can be wall-mounted. Current flat-panel TVs use either plasma or LCD screen technology.
Frame In moving picture media, whether film or video, a frame is a complete, individual picture.
Frame rate The rate at which frames are displayed. The frame rate for movies on film is 24 frames per second (24 fps). Standard NTSC video has a frame rate of 30 fps (actually 60 fields per second). The frame rate of a progressive-scan video format is twice that of an interlaced-scan format. For example, interlaced formats like 480i and 1080i deliver 30 complete frames per second; progressive formats like 480p, 720p and 1080p provide 60.
Front-projection TV See Projector.
Gain Measures the light-reflecting ability of a projection screen. The higher the number, the greater the amount of light reflected back to the viewer(s).
HDCP (High-Bandwidth Digital Content Protection) HDCP encryption is used with high-resolution signals over DVI and HDMI connections and on D-Theater D-VHS recordings to prevent unauthorized duplication of copyrighted material.
HDMI™ (High-Definition Multimedia Interface) Similar to DVI (but using much smaller connectors), the multi-pin HDMI interface transfers uncompressed digital video with HDCP copy protection and multichannel audio. Using an adapter, HDMI is backward-compatible with most current DVI connections, although any DVI-HDMI connection will pass video only, not audio. For an in-depth look at HDMI, see The Ins and Outs of HDMI.
HDMI-CEC A remote control protocol that is an optional part of the HDMI spec — CEC stands for consumer electronics control. Available from HDMI version 1.2a on, HDMI-CEC allows multiple HDMI-connected components to be operated from a single remote control without any special setup or programming. HDMI-CEC is a 2-way communications system, and up to 10 devices can be controlled in a system. Each electronics manufacturer calls this feature something different: Panasonic uses EZ-Sync, Samsung Anynet+, Sony BRAVIA Theatre Sync, Toshiba CE-LINK, LG SimpLink, etc.
HDTV (High-Definition Television) Often mistakenly used as a generic description of all digital television, HDTV specifically refers to the highest-resolution formats of the 18 original DTV formats. Although there still isn't 100% agreement among manufacturers, retailers, journalists, etc., only 1,080-line interlaced (1080i) or 720-line progressive (720p) broadcasts are generally considered to be true HDTV. 1,080-line progressive (1080p) is not an official HD broadcast format, but it is found on high-definition Blu-ray discs and some satellite TV movie broadcasts. And 1080p is now an established standard for HDTV screens.
HDTV-ready The term used to describe TVs which can display digital high-definition TV formats when connected to a separate HDTV tuner. These TVs generally have built-in tuners for receiving regular NTSC broadcasts, but not digital. An HDTV-ready TV may also be referred to as an "HDTV monitor."
Hertz (Hz) A measure of frequency, where one Hertz equals one cycle per second. In video, Hertz is used to describe a frame rate in frames per second. For example, you'll often see 24-frames-per-second video at listed as "24Hz."
Interlaced scan Interlaced scan is a way to describe how some video signals and displays form an image. America's NTSC analog television system uses 525 scanning lines to create each complete picture (frame). The frame/picture is made up of two fields: The first field has 262.5 odd lines (1,3,5...) and the second field has 262.5 even lines (2,4,6...). The odd lines are scanned (drawn on the screen) in 1/60th of a second, and the even lines follow in the next 1/60th of a second. This presents a complete frame/picture of 525 lines in 1/30th of a second.
Analog NTSC video uses interlaced scanning, as do some digital television formats. Formats that include an "i" (1080i, 480i) use interlaced scanning. In fact, these days interlaced scanning is mostly mentioned when describing video broadcasts because virtually all non-tube TV types are progressive scan by nature. And for a more complete discussion of interlaced vs. progressive scan, see our article about HDTV resolution.
Internet-ready TV TVs labeled "Internet-ready" can connect to your home network to access online content. For example, a growing number of Internet-ready TVs let you play movies from services like Netflix®, BlockBuster™, or Amazon Video On Demand™. Keep in mind that you won't be able to browse the Internet the way you do on your computer — you'll only be able to access specific sites and information based on software included in your TV. Different TV makers provide access to different Internet sites and services, and sometimes these capabilities can be enhanced by firmware updates that the manufacturer provides. Besides movie services, common examples include weather, news, social media updates, and sports scores.
A few higher-end TVs have Wi-Fi® capability, but most TVs require a wired Ethernet connection. You can still get a wireless connection with many of those TVs by adding an optional USB Wi-Fi adapter. These adapters are usually brand-specific, so shop accordingly.
Keystone correction "Keystoning" is a form of video image distortion that occurs with front projectors if the centerline of the projector's lens is not perpendicular to the screen. Keystoning results in an image which is shaped like a trapezoid rather than a rectangle — the top of the picture is wider than the bottom, or the left side is taller than the right, for example. Most front projectors include "keystone correction" to correct this distortion. Some models have vertical keystone correction, while others include both vertical and horizontal correction. Although keystone correction allows greater mounting flexibility, it is a form of processing which usually has a slight softening and dimming effect on the picture.
LCD (Liquid Crystal Display) Liquid Crystal Display technology is one of the methods used to create flat-panel TVs. Light isn't created by the liquid crystals; a "backlight" behind the panel shines light through the display. The display consists of two polarizing transparent panels and a liquid crystal solution sandwiched in between. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal acts like a shutter, either allowing light to pass through or blocking the light. The pattern of transparent and dark crystals forms the image.
See our articles on flat-panel LCD technology and rear-projection LCD TVs for more details. There are also LCD-based projectors.
LCoS (Liquid Crystal on Silicon) A projection TV technology based on LCD. With LCoS, light is reflected from a mirror behind the LCD panel rather than passing through the panel. The control circuitry that switches the pixels on and off is embedded further down in the chip so it doesn't block the light, which improves brightness and contrast. This multilayered microdisplay design can be used in rear-projection TVs and projectors. TV makers use different names for their LCoS technologies — Sony uses SXRD™, while JVC uses D-ILA™ or HD-ILA™.
LED (Light Emitting Diode) An LED is a semiconductor diode that typically emits a single wavelength of light when an electric current passes through it. Different colors can be generated based on the material used; common colors include red, green, blue, and white.
White LEDs are used as backlights in some newer flat-panel LCD TVs, while colored LEDs are used in some recent DLP rear-projection TVs.
LED TV A term sometimes used for LCD TVs that use an LED backlight instead of a conventional fluorescent one. An LED backlight improves contrast and delivers a wider range of colors, for a more lifelike picture. TVs with LED backlights also generally consume less power than those that use fluorescent backlights.
Some of these TVs use a series of LEDs arranged in a grid behind the LCD panel. And some TVs with these LED grids feature "local dimming", which allows the TV to display light and dark portions of the same image more accurately. Other sets are "edge-lit," meaning that the LEDs are located around the sides of the panel instead of in a grid behind it. While edge-lit LED TVs don't offer local dimming, they generally have thinner cabinets — sometimes barely more than an inch deep. For more information, see our video on LCD backlighting.
Letterboxed video A method for displaying the entire picture as seen in a movie theater on a TV screen. The resulting image width is much greater than its height. On an old-fashioned TV screen with 4:3 aspect ratio, letterboxed videos appear with horizontal black bars above and below the image. You will often see these black bars when watching movies on a widescreen TV, too. To learn more about aspect ratios and ways to deal with those black bars, see our aspect ratio article.
Light output Measures the amount of light produced by a video display, and is an especially important spec for projectors. Expressed in "lumens" or "ANSI lumens," with a higher number indicating greater light output, which results in a brighter picture.
Local dimming A feature found on some LED-backlit TVs that allows them to dim or even completely shut off different sections of the LED grid independently. These TVs can accurately display both light and dark portions of an image at the same time, for greater contrast and a more lifelike picture.
Lumen The unit of measure for light output of a projector. Different manufacturers may rate their projectors' light output differently. "Peak lumens" is measured by illuminating an area of about 10% of the screen size in the center of the display. This measurement ignores the reduction in brightness at the sides and corners of the screen.
The more conservative "ANSI lumens" (American National Standards Institute) specification is made by dividing the screen into 9 blocks, taking a reading in the center of each, and averaging the readings. This number is usually 20-25% lower than the peak lumen measurement.
Luminance The brightness or black-and-white component of a color video signal. Determines the level of picture detail.
Megahertz (MHz) Equal to one million Hertz. Video signal bandwidth is typically expressed in megahertz.
Microdisplay A general term covering several different technologies used in digital rear-projection TVs and projectors. These displays produce large images; the "micro" refers to the postage stamp-sized image chips that create the images. Microdisplay types include DLP, LCD, and LCoS. For a comparison of rear-projection microdisplay types, and details on how each technology works, see our Choosing a Big-screen Projection TV article.
MPEG (Moving Picture Experts Group) The organization charged with developing video and audio encoding standards. On the video front, consumers are most likely to encounter the MPEG-2 and MPEG-4 compression formats, or "codecs." These formats are capable of producing very high quality video by employing an adaptive, variable bitrate process that can allocate more bits for complex scenes involving a lot of motion, while reducing the bits in static scenes.
· MPEG-2: Used for over-the-air digital television broadcasts, standard DVDs, some Blu-ray Disc and HD DVD discs, and small-dish satellite TV (DIRECTV and DISH).
· MPEG-4: This newer format is more efficient than MPEG-2, meaning it can deliver the same picture quality as MPEG-2 using a lower bitrate. Some Blu-ray Discs and HD DVDs, and newer DIRECTV and DISH satellite gear use MPEG-4.
NTSC (National Television System Committee) The North American 525-line analog broadcast TV standard, which was established over 50 years ago. Although it is referred to as a "525-line" standard, we're only able to see 480 lines on a TV display. The ATSC digital broadcast standard will replace NTSC as of June 12, 2009.
OLED (Organic Light Emitting Diode) OLED is an up-and-coming display technology that can be used to create flat-panel TV TVs. An OLED panel employs a series of organic thin films placed between two transparent electrodes. An electric current causes these films to produce a bright light. A thin-film transistor layer contains the circuitry to turn each individual pixel on and off to form an image. The organic process is called electrophosphorescence, which means the display is self-illuminating, requiring no backlight. OLED panels are thinner and lighter than current plasma or LCD HDTVs, and have lower power consumption. Only small OLED screens are available at this time, but larger screens should be available by 2009.
Overscan The portion of a video image that lies outside a TV's visible screen area. The amount of overscan varies from model to model, but typically ranges between 5% and 10% or the total image. Some recent TVs with "pixel-by-pixel" or "dot-by-dot" display modes are capable of showing the full image, with no overscan. This is especially advantageous when viewing 1080i or 1080p content on a 1080p TV.
Pan-and-scan The process of transferring a widescreen movie or other source material to videocassette, DVD, or broadcast so that it fits the squarish 4:3 aspect ratio of most old-fashioned TVs. This results in a significant amount of lost picture information, particularly in the width of the image. Most new HDTVs use the wider 16:9 aspect ratio, which can display all or most of the original picture of widescreen material.
At the beginning of a movie on videocassette, you'll usually see a disclaimer about the movie having been "...formatted to fit your TV." That means it's been converted to pan-and-scan.
Picture-in-picture (PIP) There are two flavors of picture-in-picture: 1-tuner PIP models require that you connect a VCR or other video component to provide the source for your second picture. 2-tuner PIP models have two built-in TV tuners, so you can watch two channels at once using only the TV.
Originally, PIP allowed viewing of multiple channels or sources by creating a small inset image overlaid on the main image. With the shift to widescreen displays, the inset type of PIP is gradually being replaced by "split screen" designs that are sometimes referred to as POP (picture-outside-picture) or PAP (picture-and-picture).
Pillar-boxed video The pillar-box effect occurs in widescreen 16:9 video displays when vertical black bars are placed at the sides of a non-widescreen 4:3 image. The smaller the size of the pixels in an image, the greater the resolution. To learn more about aspect ratios and ways to deal with black bars, see our aspect ratio article.
Pixel Short for "picture element." The smallest bit of data in a video image. As pixel size gets smaller, more pixels can fit in the same screen area, increasing picture resolution.
Pixel response time The amount of time it takes for a single pixel in a video display to switch from active to non-active; it is measured in milliseconds (ms). If a display's response time is too slow, faint motion trails may be visible following fast-moving on-screen objects. Pixel response time is an important performance spec for all types of digital flat-panel and projection displays although it's rarely listed for non-LCD TVs. For smooth, accurate playback of high-quality video material, look for a response time of 8 ms or less.
Plasma Plasma technology is one of the methods used to create flat-panel TVs. The display consists of two transparent glass panels with a thin layer of pixels sandwiched in between (think of this layer as containing somewhere between 800,000 and two million tiny fluorescent bulbs — the pixels). Each pixel is composed of three gas-filled cells or sub-pixels (one each for the red, green and blue primary colors). A grid of tiny electrodes applies an electric current to the individual cells, causing the gas to ionize. This ionized gas (plasma) emits high-frequency UV rays which stimulate the cells' phosphors, causing them to glow, which creates the TV image. For more info on how plasma technology works, see our LCD vs. Plasma article.
Progressive scan Some digital television broadcast formats (720p, 480p), and most DVD players, use a type of video signal known as progressive scan. Instead of splitting each video frame into two sequential fields like analog interlaced NTSC video, progressive-scan video displays the entire frame in a single sweep. For example, where standard NTSC video displays 30 frames (60 fields) per second, progressive scan displays 60 complete frames per second.
Another way to look at it is that progressive-scan video has twice as much picture information as the equivalent interlaced video format. Progressive-scan picture quality is more filmlike, with more fine detail and less flicker. Virtually all of today's digital TVs are progressive-scan displays, with screen resolutions of 720p, 768p or 1080p. For a more in-depth discussion of progressive vs. interlaced scan, see our article about video resolution.
Projector A video display device that projects a large image onto a physically separate screen. The projector is typically placed on a table, or ceiling-mounted. Projectors, sometimes referred to as front-projection systems, can display images up to 10 feet across, or larger. Old-fashioned large, expensive CRT-based projectors have been replaced by compact, lightweight, lower-cost digital projectors using DLP, LCD or LCoS technology.
QAM (Quadrature Amplitude Modulation) A digital modulation format used for downstream transmission in cable TV systems — commonly used for cable HDTV.
QAM tuner A QAM tuner allows cable subscribers to tune in unscrambled cable channels without a separate set-top box, including high-definition channels, if the cable service provider offers them.
Rainbow effect A visual artifact associated with single-chip DLP-based rear- and front-projection displays. Fortunately, only a few people see these momentary flashes of color, and fewer still find these "rainbows" to be distracting. For those unlucky few, rainbows typically occur when the viewer's eyes dart away from the screen. Rainbows result from DLP's use of a color wheel, which causes the three primary colors — red, green, and blue — to be projected sequentially, rather than continuously. Some recent single-chip DLP TVs have replaced the lamp-and-color-wheel system with colored LEDs, which reduce this effect. And rainbows aren't an issue for 3-chip DLP projectors because each primary color has its own dedicated image chip, so no color wheel is needed.
Rear-projection TV Typically referred to as "big-screen" TVs, these large-cabinet TVs generally have built-in screens measuring at least 40". Unlike the bulky CRT-based rear-projection TVs from years ago, today's "tabletop" rear-projection TVs are relatively slender and light. These TVs use digital microdisplay technologies like DLP, LCD, and LCoS. For an in-depth look at these new rear-projection TVs, see our Choosing a Big-screen Projection TV article.
Resolution In video terms, resolution refers to the amount of picture detail provided by a video signal or display. Although you may hear references to "lines of resolution," that's mainly a holdover from the tube-TV era. Today's digital TVs create their images using a grid of pixels; more pixels generally equals higher resolution. This grid has a fixed number of pixels, which means if the TV receives any video signal with a different resolution, the TV will scale that signal to fit the screen's pixels.
The picture quality you see on your TV depends on two factors: the resolution of the TV's screen and the resolution of the video signal. Since video images are always rectangle-shaped, there is both horizontal resolution and vertical resolution to consider.
· Vertical resolution: The number of horizontal lines (or pixels) that can be resolved from the top of an image to the bottom. (Think of hundreds of horizontal lines or dots stacked on top of one another.) The vertical resolution of the analog NTSC TV standard is 525 lines. But some lines are used to carry other data like closed-captioning text, test signals, etc., so we end up with about 480 lines in the final image. So, all of the typical NTSC sources — VHS VCRs, cable and over-the-air broadcast TV (analog), non-HD digital satellite TV, DVD players, camcorders, etc. — have vertical resolution of 480 lines. DTV (Digital Television) signals have vertical resolution that ranges from 480 pixels for SDTV, to 720 or 1080 pixels for true HDTV. If you're comparing TVs or video sources, vertical resolution is what's usually listed: 480p, 720p, 1080p, etc.
· Horizontal resolution: The number of vertical lines (or pixels) that can be resolved from one side of an image to the other. Horizontal resolution is a slightly trickier concept, at least for analog video, because while the vertical resolution of all analog video sources is the same (480 lines), the horizontal resolution varies according to the source. Some common examples: VHS VCRs (240 lines), analog TV broadcasts (330 lines), non-HDTV digital satellite TV (up to 380 lines), and DVD players (540 lines). DTV signals have horizontal resolution that ranges from 640 pixels for SDTV, to 1280 pixels (for 720p HDTV) or 1920 pixels (for 1080i and 1080p HDTV).
Multiplying the horizontal resolution by the vertical resolution gives you the total screen resolution. For example, a 1080p screen has 1920 horizontal pixels by 1080 vertical pixels — 1920 x 1080 = 2,073,600 pixels. For an in-depth look at high-definition video resolution, see our article about video resolution.
RF (radio frequency) jack Sometimes referred to as a "75-ohm coaxial" connection, this kind of jack is commonly used for bringing signals from antennas and other sources outside the home to components with some type of tuner, such as cable boxes, HDTV tuners, VCRs, satellite receivers, TVs, etc. A 75-ohm coaxial cable can carry video and stereo audio information simultaneously. However, as a way of making a video connection between components, RF is inferior to composite, S-video, component video, and HDMI. RF cable connectors (often called "F-type" connectors) either screw onto the 75-ohm jack, or just push on to connect. See our connections glossary for more info.
There are different types of coaxial cable. Standard coaxial cable is stamped "RG-59"; higher-quality "RG-6" cable features better shielding, and exhibits less high-frequency loss over longer runs. (For connecting DBS satellite systems, it's important to use RG-6 cable to correctly pass the entirety of the digital signal.)
Scaler Circuitry that converts a video signal to a resolution other than its original format. Scaling can involve upconversion or downconversion, and may also include a conversion between interlaced- and progressive-scan formats. A scaler can be built into a TV, HDTV tuner, DVD player, or home theater receiver, or may be a standalone component.
Scanning lines On CRT-based TVs, the number of scanning lines measures the screen's resolution. Scanning refers to an electron gun tracing horizontal lines across a phosphor-coated screen, painting each video frame as a series of lines. Although you may still hear the term "scan lines" used when describing digital TVs that use plasma, LCD, or other pixel-based technologies, it's not really accurate. These newer TV types flash each complete screen image simultaneously without any type of actual scanning.
SDTV (Standard-Definition Television) SDTV refers to the non-high-definition formats in the ATSC digital television standard. SDTV pictures can have either 4:3 or 16:9 aspect ratio. Picture and sound is clearer than analog NTSC video, with picture resolution of 480i or 480p. These digital signals require less bandwidth than analog signals, allowing TV stations to simultaneously broadcast multiple channels of programming in place of a single analog channel; this is called "multicasting."
Set-top box (STB) Also called converter boxes, these receivers convert broadcasts (either over-the-air broadcast HDTV, analog cable, digital cable, satellite, or Internet-based IPTV) for display on a television.
S-video Found on nearly all of the TVs we sell, this 4-pin connector usually provides a sharp, clear picture by transmitting the chrominance and luminance portions of a video signal separately. The signals can then be processed separately, reducing interference. Direct S-video connections generally outperform composite connections when hooking up video components like DVD players, DBS receivers, and S-VHS and Hi8 recorders and camcorders. However, they don't look as sharp as HD-capable connections like component video, and HDMI. See our connections glossary for more info.
SXRD™ — Silicon X-tal (Crystal) Reflective Display Sony's variation of LCoS projection display technology.
Tube TV See CRT.
Upconversion The term used to describe the conversion of a lower resolution to an apparently higher one. This process increases the number of pixels and/or frame rate and/or scanning format used to represent an image by interpolating existing pixels to create new ones at closer spacing.
V-Chip Several years ago the FCC (Federal Communications Commission) began requiring that TVs include "V-Chip" technology to block the display of television programs based on their rating. All sets with screens 13 inches or larger manufactured after January 1, 2000 must include the V-Chip. Broadcasters are required to encode an electronic signal in TV programs indicating the level of violence, language, and sexual content. Parents can program the TV with a rating so that when the the V-Chip reads a show's signal, it will prevent it from displaying if it is above the rating.
The rating system, known as "TV Parental Guidelines," was established by the National Association of Broadcasters, the National Cable Television Association and the Motion Picture Association of America. These ratings display on the TV screen for the first 15 seconds of rated programs.
Viewing angle Measures a video display's maximum usable viewing range from the center of the screen, with 180° being the theoretical maximum. Most often, the horizontal (side to side) viewing angle is listed, but sometimes both horizontal and vertical viewing angles are provided. For most home theater setups, horizontal viewing angle is more critical.
Widescreen When used to describe a TV, widescreen generally refers to an aspect ratio of 16:9, which is the optimum ratio for viewing anamorphic DVDs and HDTV broadcasts.
Wobulation A technique originally invented by Hewlett-Packard for its ink jet printers. Texas Instruments, developer of DLP display technology, employs wobulation in some of its image chips used in rear-projection TVs. Like interlacing, wobulation shows half the picture at a time, but displays the two halves so rapidly that our eyes combine the two parts into one. A 1080p DLP TV can display images with 1920 x 1080 pixels, yet its DMD (Digital Micromirror Device) image chip has 960 x 1080 mirrors. Half the image is displayed, then a separate pivoting reflective panel called an "actuator" shifts the display a half pixel's width to the side. This all happens fast enough to generate 60 full frames per second, for a clean progressive-scan image. Texas Instruments calls this technique SmoothPicture™, and it is also often referred to as "pixel-shifting."
x.v.Color (xvYCC color space) A high-definition video color space that is supported by many HDTVs beginning in 2007 (generally models with HDMI v1.3 inputs). The x.v.Color standard supports 1.8 times as many colors as the ATSC HDTV standard. Although there are HD camcorders that support x.v.Color, there are no broadcast or packaged consumer high-def sources that support it. Even if both your HDTV and high-def player support x.v.Color, your video source must be encoded with it as well or you won't see the wider color range.
1080p 1080p is a high-definition video format with resolution of 1920 x 1080 pixels. The "p" stands for progressive scan, which means that each video frame is transmitted as a whole in a single sweep. The main advantage of 1080p TVs is that they can display all high-definition video formats without downconverting, which sacrifices some picture detail.
1080p TVs display video at 60 frames per second, so this format is often referred to as 1080p60. The video on most high-definition discs (Blu-ray and HD DVD) is encoded at film's native rate of 24 frames per second, or 1080p24. For compatibility with most current 1080p TVs, high-definition players internally convert the 1080p24 video to 1080p60. By late 2007, many HDTVs included the ability to accept a 1080p24 signal directly. These TVs don't actually display video at 24 frames per second because that would cause visible flicker and motion stutter. The TV converts the video to 60 frames per second or whatever its native display rate is. The ideal situation would be to display 1080p24 at a multiple of 24 frames per second, like 72, 96, or 120 frames per second, to avoid the motion judder caused by 3-2 pulldown, which is required when converting 24-frames-per-second material to 60 frames per second.
120Hz refresh rate The digital display technologies (LCD, plasma, DLP, LCoS, etc.) that have replaced picture tubes are progressive scan by nature, displaying 60 video frames per second — often referred to as "60Hz." HDTVs with 120Hz refresh rate employ sophisticated video processing to double the standard rate to 120 frames per second by inserting either additional video frames or black frames. Because each video frame appears for only half the normal amount of time, on-screen motion looks smoother and more fluid, with less smearing. It's especially noticeable viewing fast-action sports and video games. This feature is available on an increasing number of flat-panel LCD TVs.
16:9 See aspect ratio and widescreen.
240Hz refresh rate 240Hz refresh rate reduces LCD motion blur even more than 120Hz refresh rate. 240Hz processing creates and inserts three new video frames for every original frame. Most "240Hz" TVs operate this way, but some models use "pseudo-240Hz" technology which combines 120Hz refresh rate with high-speed backlight scanning. An example of the pseudo-240Hz approach, which can also be very effective, is Toshiba's ClearScan 240™ technology.
3D TV By adding a sense of picture depth and dimensionality, 3D TVs create a more engaging viewing experience that's similar to watching a 3D movie in a theater. Like 3D movies, 3D TV requires that each viewer wear special glasses to see the 3D effects. 3D TV requires the use of wireless "active shutter" glasses.
Whether a 3D TV uses LCD or plasma screen technology, all 3D TVs use a specially-designed screen that can display two different versions of a video image by alternating the video frames at very high speed. 3D video is basically two full-resolution 1080p images, one for your left eye and one for your right. The shutter glasses' lenses darken and lighten rapidly in coordination with the screen's flashing images. The timing of the shutter glasses is wirelessly controlled by an "emitter" that is usually built into the TV. The system creates an immersive viewing experience. True 3D viewing also requires a 3D video source, like a 3D Blu-ray player playing a 3D movie.
For more info, see our intro to 3D, or check out our in-depth 3D TV FAQ.
3-2 pulldown processing Sophisticated video processing common in HDTVs and progressive-scan DVD players. It corrects for artifacts and distortion that occur when film-based material (at 24 frames per second) is converted to video (30 frames per second), then de-interlaced to create a progressive-scan signal. For a more in-depth explanation, see our DVD Player Glossary.
Active shutter glasses To see three-dimensional effects on a 3D TV screen, each viewer must wear a special type of 3D glasses called "shutter" glasses. Also called "active" glasses, these battery-powered liquid-crystal glasses are able to lighten or darken hundreds of times per second to alternately block out the left or right lens in coordination with the video frames flashing on screen. The lenses aren't displaying images, just switching between dark and clear. To anyone not wearing shutter glasses, a 3D TV picture will look blurry. Active glasses are far more technologically advanced than the disposable 3D glasses handed out in movie theaters.
For more info, see our intro to 3D, or check out our in-depth 3D TV FAQ.
ALiS (Alternate Lighting of Surfaces) A type of high-definition plasma TV panel designed for optimum performance when displaying 1080i material. On a typical progressive-scan plasma TV, all pixels can be illuminated at any given instant. With an ALiS plasma panel, alternate rows of pixels are illuminated so that only half the panel's pixels can be illuminated at any moment (somewhat similar to interlaced-scanning on a CRT-type TV). ALiS-based plasmas make up a small part of the overall market; TV makers that use ALiS panels include Hitachi and Fujitsu.
Anamorphic video Refers to widescreen video images that have been "squeezed" to fit a narrower video frame when stored on DVD. These images must be expanded (un-squeezed) by the display device. Most of today's TVs employ a screen with 16:9 aspect ratio, so that anamorphic and other widescreen material can be viewed in its proper proportions. When anamorphic video is displayed on an old-fashioned TV with a 4:3 screen, images appear unnaturally tall and narrow.
Anti-blur technology A technology that reduces image "smearing" or "motion blur" that can sometimes occur with LCD TVs. LCD televisions with anti-blur technology can deliver smoother, cleaner images than those without, particularly during fast-paced scenes. This anti-blur video processing is usually described as 120Hz refresh rate or 240Hz refresh rate. TV makers have their own proprietary names for anti-blur technology; examples include Sony's Motionflow™ and Samsung's Auto Motion Plus.
Artifacts Unwanted visible effects in the picture created by disturbances in the video transmission or processing. Examples include "dot crawl" or "hanging dots" in analog pictures, or "pixelation" in digital pictures.
Aspect ratio The ratio of width to height for an image or screen. The North American NTSC television standard uses the squarish 4:3 (1.33:1) ratio. HDTVs use the wider 16:9 ratio (1.78:1) to better display widescreen material like high-definition broadcasts and DVDs. See our article about aspect ratio to better understand it and get pointers on troubleshooting some common aspect ratio problems.
ATSC (Advanced Television Standards Committee) Formed to establish technical standards for the U.S. digital television system. A TV tuner that can receive local over-the-air digital broadcasts is often called an ATSC tuner.
Audio Return Channel This feature is available on some 2010 TVs and audio/video components with HDMI 1.4 connections. A TV with Audio Return Channel allows a single HDMI cable to send the audio from the TV's built-in tuner "upstream" to a compatible A/V receiver, eliminating the need for a separate optical or coaxial digital audio cable.
Audio/video inputs Using a TV's direct audio/video inputs to connect a DVD player, VCR, camcorder or other video component provides improved picture and sound quality compared to using the everything-on-one-wire RF antenna-style input. If your TV is old enough that it only has RF-type inputs, that's reason enough to consider replacing it, since many newer video components don't include an RF output.
Backlight scanning An anti-blur technology used in some LCD TVs. Typical LCDs use a fluorescent backlight that shines constantly, which can contribute to motion blur. LCD models with backlight scanning have a special type of fluorescent backlight that pulses at very high speed, which has the effect of reducing motion blur. Some recent TVs use backlight scanning along with 120Hz refresh rate for even greater blur reduction.
Big-screen TV See rear-projection TV.
Bitrate Measured as "bits per second," and used to express the rate at which data is transmitted or processed. The higher the bitrate, the more data is processed and, typically, the higher the picture resolution. Digital video formats typically have bitrates measured in megabits-per-second (Mbps). (One megabit equals one million bits.) The maximum bitrate for standard DVDs is 11Mbps; for over-the-air HDTV broadcasts, it's 19.4Mbps. High-definition discs have even higher maximum bitrates: 36Mbps for HD DVD and 54Mbps for Blu-ray Disc™.
Black level Describes the appearance of darker portions of a video image. Black is the absence of light, so to create the black portions of an image, a display must be able to shut off as much light as possible. Displays with good black level capability not only produce deeper blacks, but also reveal more details and shading in dark or shadowy scenes.
Burn-in Screen burn-in can affect TVs that use a phosphor coating on the screen. It was an issue for early plasma TVs. Burn-in can occur when a static image — like a non-widescreen 4:3 image with vertical black bars on the sides, or a scrolling stock or news ticker — remains on-screen for an extended period. These images can become etched into the phosphor coating, leaving faint impressions. In recent years, TV makers have significantly reduced plasma power consumption and refined the panel technology to dramatically reduce the chances of burn-in occurring, while also including the ability to erase burn-in effects. New plasma TVs are nearly immune to screen burn-in. To prevent any possibility of burn-in, plasma owners should follow the manufacturer's guidelines for adjusting the TV's brightness and contrast settings when the TV is new. For tips on TV settings, see our article about optimizing your TV's picture.
CableCARD™ A removable security card available from cable TV providers. It allows a TV with a compatible CableCARD slot to receive digital cable programming, including premium and HD channels, without using a separate set-top box. The FCC (Federal Communications Commission) began requiring service providers to make CableCARDs available as of July 1, 2004. Contact your local cable provider for details regarding the availability and costs of CableCARD-related services. See our article about Cable TV more details about CableCARDs.
Chrominance The color component of a video signal that includes information about hue (shade) and saturation (intensity).
Color resolution (color bit depth) The color resolution of HDTVs and other video gear is typically described as a color bit depth such as "8-bit" or "10-bit." Color resolution indicates how fine the gradations can be between different shades of the same color — it's a measure of color accuracy. Nearly all consumer video equipment is 8-bit, and 8-bit resolution allows 256 possible shades. That's 256 each for the red, green, and blue primary colors. To calculate the total number of possible colors an 8-bit TV can reproduce, you multiply 256 x 256 x 256, which equals 16.7 million. Some TVs use 10-bit panels and video processing. That may not sound like much more, but 10-bit resolution means 1024 possible shades and over one billion total colors.
Color space A "color space" is a defined range of colors, and is usually associated with an industry standard. Examples of color spaces that relate to television and video equipment include NTSC for analog video, and ATSC and x.v.Color for high-definition video. A wider color space offers the potential for deeper hues. Few current HDTVs are even capable of reproducing the full NTSC color space, let alone the wider ATSC color space or the much wider x.v.Color color space. When you see a TV's color range expressed as a percentage of a color space, it's almost always NTSC.
Comb filter A comb filter's task is to remove residual chrominance (color) information from the luminance (brightness) signal. Comb filtering enhances fine detail, cleans up image outlines, and eliminates most extraneous colors from analog video signals. A comb filter is very effective for composite video signals, but is not required and not used for S-video or component video since those connections carry the chrominance and luminance information separately. There are 4 different types of comb filters found in today's TVs, listed here in order of ascending quality:
· Glass: may also be referred to as an "analog" comb filter.
· 2-line Digital: compares consecutive scanning lines within one field of video and makes adjustments to reduce cross-color interference.
· 3-line Digital: compares 3 scanning lines within a field of video. By comparing more picture information, a 3-line filter further reduces color bleeding and dot crawl.
· 3D Digital: not only analyzes consecutive scanning lines within a field, but also analyzes the preceding and following fields. Results in improved color purity and a more stable video image, and nearly eliminates dot crawl and color bleeding. Also called 3D Y/C.
Component video The three-jack component video connection splits the video signal into three parts (one brightness and two color signals). Compared to other analog video connections, component video has increased bandwidth for color information, resulting in a more accurate picture with clearer color reproduction and less bleeding. Component video is the only type of analog video connection that can pass high-definition signals, and provides better picture quality than S-video or composite video connections. See our connections glossary for more info.
Composite video A single video signal that combines brightness and color information. A composite signal is better than an RF signal, but not as good as S-video. A composite video jack is usually a single RCA-type. See our connections glossary for more info.
Contrast ratio Measures the difference between the brightest whites and the darkest blacks that a TV can display. The higher the contrast ratio, the better a TV will be at showing subtle color details, and the better it will look in rooms with more ambient room light. Contrast ratio is one of the most important specs for all TV types.
There are actually two different ways of measuring a TV's contrast ratio. Static contrast ratio measures the difference between the brightest and darkest images a TV can produce simultaneously (sometimes called on-screen contrast ratio). The ratio of the brightest and darkest images a TV can produce over time is called dynamic contrast ratio. Both specs are meaningful, but the dynamic spec is often four or five times higher than the static spec, so make sure you're comparing apples to apples.
CRT (Cathode-Ray Tube) A CRT ("picture tube") is a specialized vacuum tube in which images are created when an electron beam scans back and forth across the back side of a phosphor-coated screen. Each time the beam makes a pass across the screen, it lights up a horizontal line of phosphor dots on the inside of the glass tube. This beam rapidly draws hundreds of these lines from the top to the bottom of the screen, creating the image.
The old-fashioned "direct-view" TVs most people grew up watching have a single large picture tube, while CRT-based rear-projection and front-projection TVs use three CRTs: one each for the red, green, and blue primary colors.
Deep Color A color resolution standard associated with high-definition TVs and video gear that include HDMI 1.3 connections. Deep Color supports 10-bit, 12-bit and 16-bit color bit depths, up from 8-bit, which is the current standard for consumer video. All earlier versions of HDMI supported 8-bit color. (Because video is based on three primary colors, you'll sometimes see Deep Color described as 30-bit, 36-bit and 48-bit.) A higher color bit depth enables finer gradations between different shades of the same color, for smoother gradients and reduced color banding. Deep Color gives TVs the potential to display billions rather than millions of colors, but in order to see that improvement, the entire video production chain has to use it (camera, editing, format, player, display). See color resolution.
De-interlacing The process of converting an interlaced-scan video signal (where each frame is split into two sequential fields) to a progressive-scan signal (where each frame remains whole). De-interlacers are found in HDTVs and progressive-scan DVD players. More advanced de-interlacers include a feature called 3-2 pulldown processing.
Digital audio output A connection found on HDTVs and HDTV tuners for sending the Dolby Digital soundtrack of HDTV broadcasts to an A/V receiver with Dolby Digital decoding. The two most common types of digital output are coaxial and Toslink optical.
D-ILA™ (Direct-drive Image Light Amplification) JVC's proprietary variation of LCoS projection display technology.
Direct-view TV A general term for non-projection types of TVs, which include conventional tube TVs and flat-panel plasma and LCD TVs.
DLNA DLNA, short for Digital Living Network Alliance, is a collaboration among more than 200 companies, including Sony, Panasonic, Samsung, Microsoft, Cisco, Denon and Yamaha. Their goal is to create products that connect to each other across your home network, regardless of manufacturer, so you can easily enjoy your digital and online content in any room.
While all DLNA-compliant devices are essentially guaranteed to work together, they may not be able to share all types of media. For example, a DLNA-certified TV may be able to display digital photos from a DLNA-certified media server, but not videos.
DLP™ (Digital Light Processing) A projection TV technology developed by Texas Instruments, based on their Digital Micromirror Device (DMD) microchip. Each DMD chip has an array of tiny swiveling mirrors which create the image. Depending on the TV's resolution, the number of mirrors can range from several hundred thousand to over two million. DLP technology is used in both front- and rear-projection displays.
There are two basic types of DLP projector. "Single-chip" models, which include virtually all rear-projection DLP TVs, use a single DMD chip, with color provided by a spinning color wheel or colored LEDs. "3-chip" projectors dedicate a chip to each primary color: red, green, and blue. While 3-chip models are considerably more expensive, they completely eliminate the rainbow effect, which is an issue for a small minority of viewers.
Dolby® Digital A discrete multichannel digital audio format that is the official audio standard for HDTV (and DVD). Dolby Digital is normally associated with 5.1-channel surround sound. Though this channel configuration is the most common, it is only one of several possible variations — a Dolby Digital soundtrack can mean anything from 1 to 5.1 channels. To learn about the various surround sound options available, see our article about surround sound formats.
Downconversion All digital TV display technologies have screens with a fixed number of pixels for displaying images. If a video source has a higher resolution than the screen's resolution, the TV will automatically downconvert the video signal to fit the screen. Downconversion reduces image detail, but downconverted pictures can still look very sharp. A good example is a 1080i HDTV broadcast displayed on a 720p TV.
DTV (Digital Television) A general term for the ATSC digital broadcast TV standard, which replaced the NTSC analog broadcast system. DTV comes in two basic flavors: widescreen, high-quality HDTV (High-Definition Television) with Dolby Digital audio, and medium-quality SDTV (Standard-Definition TV).
DVI (Digital Visual Interface) A multi-pin, computer-style connection intended to carry high-resolution video signals from video source components (such as older HD-capable satellite and cable boxes, and upconverting DVD players) to HD-capable TVs with a compatible connector. Most (but not all) DVI connections use HDCP (High-bandwidth Digital Content Protection) encryption to prevent piracy. In consumer electronics products, DVI connectors have been almost completely replaced by HDMI connectors, which carry both video and audio. You can use an adapter to connect a DVI-equipped component to an HDMI-equipped TV, or vice versa, but a DVI connection can never carry audio. See our connections glossary for more info.
Dynamic backlighting Found on many LCD TVs, this feature dynamically adjusts the brightness of the backlight in response to the picture content of whatever you're watching, to improve picture contrast and reduce power consumption. It helps the TV display both bright outdoor scenes and dark indoor scenes with greater accuracy. Use of dynamic backlighting contributes to the very high "dynamic contrast ratio" specs provided by TV makers.
EDTV (Enhanced-Definition Television) A virtually obsolete class of televisions, generally flat-panel LCD or plasma, that displays signals in 480-line progressive-scan (480p) mode. 480p screen resolution is superior to standard analog TV (480i), but not as sharp as true HDTVs (720p or 1080p).
Electronic program guide (EPG) Provides an on-screen listing of available channels and program data for an extended time period (typically 36 hours or more). Examples of program guides include subscription services like TiVo® and free guides like TV Guide® On Screen. To learn more about EPG features and capabilities, see our article about TV Guide On Screen.
Emitter (for 3D TV) An important part of a 3D TV system is the "emitter" that precisely controls the timing of the active shutter glasses. The emitter communicates with the glasses wirelessly via infrared beams. "3D-ready" TVs include a built-in emitter, while "3D-capable" TVs require that you add an outboard emitter box.
For more info, see our intro to 3D, or check out our in-depth 3D TV FAQ.
Energy Star® compliant A certification for consumer electronics products indicating energy efficiency. The Energy Star program was introduced by the EPA (Environmental Protection Agency) in 1992, and set standards for product power consumption in "standby" mode. (When a component is switched off but still plugged into an AC power source, it continues to draw a small amount of power in standby mode to keep circuits active and ready for quick turn-on.) In November 2008, the EPA created the more stringent Energy Star 3.0 specification, which requires energy efficiency when products are in use, as well as when they are in standby mode. Products that meet the new spec are up to 30% more energy efficient than previous models.
For information specifically relating to TV energy use, including our own in-house testing program, see our article on TV Power Consumption.
Ethernet port An Ethernet port on a TV enables a connection to a home network and/or the Internet. What you can do once you're on the network varies by model. Typically, only a select number of websites are accessible, and capabilities may be limited by the speed of your Internet connection.
Field In interlaced-scan video, each complete frame is split into 2 sequential fields, each of which contains half the picture information. One field contains the odd scanning lines, and the other field the even lines.
Flat-panel TV Any ultra-thin, relatively lightweight TV — especially those which can be wall-mounted. Current flat-panel TVs use either plasma or LCD screen technology.
Frame In moving picture media, whether film or video, a frame is a complete, individual picture.
Frame rate The rate at which frames are displayed. The frame rate for movies on film is 24 frames per second (24 fps). Standard NTSC video has a frame rate of 30 fps (actually 60 fields per second). The frame rate of a progressive-scan video format is twice that of an interlaced-scan format. For example, interlaced formats like 480i and 1080i deliver 30 complete frames per second; progressive formats like 480p, 720p and 1080p provide 60.
Front-projection TV See Projector.
Gain Measures the light-reflecting ability of a projection screen. The higher the number, the greater the amount of light reflected back to the viewer(s).
HDCP (High-Bandwidth Digital Content Protection) HDCP encryption is used with high-resolution signals over DVI and HDMI connections and on D-Theater D-VHS recordings to prevent unauthorized duplication of copyrighted material.
HDMI™ (High-Definition Multimedia Interface) Similar to DVI (but using much smaller connectors), the multi-pin HDMI interface transfers uncompressed digital video with HDCP copy protection and multichannel audio. Using an adapter, HDMI is backward-compatible with most current DVI connections, although any DVI-HDMI connection will pass video only, not audio. For an in-depth look at HDMI, see The Ins and Outs of HDMI.
HDMI-CEC A remote control protocol that is an optional part of the HDMI spec — CEC stands for consumer electronics control. Available from HDMI version 1.2a on, HDMI-CEC allows multiple HDMI-connected components to be operated from a single remote control without any special setup or programming. HDMI-CEC is a 2-way communications system, and up to 10 devices can be controlled in a system. Each electronics manufacturer calls this feature something different: Panasonic uses EZ-Sync, Samsung Anynet+, Sony BRAVIA Theatre Sync, Toshiba CE-LINK, LG SimpLink, etc.
HDTV (High-Definition Television) Often mistakenly used as a generic description of all digital television, HDTV specifically refers to the highest-resolution formats of the 18 original DTV formats. Although there still isn't 100% agreement among manufacturers, retailers, journalists, etc., only 1,080-line interlaced (1080i) or 720-line progressive (720p) broadcasts are generally considered to be true HDTV. 1,080-line progressive (1080p) is not an official HD broadcast format, but it is found on high-definition Blu-ray discs and some satellite TV movie broadcasts. And 1080p is now an established standard for HDTV screens.
HDTV-ready The term used to describe TVs which can display digital high-definition TV formats when connected to a separate HDTV tuner. These TVs generally have built-in tuners for receiving regular NTSC broadcasts, but not digital. An HDTV-ready TV may also be referred to as an "HDTV monitor."
Hertz (Hz) A measure of frequency, where one Hertz equals one cycle per second. In video, Hertz is used to describe a frame rate in frames per second. For example, you'll often see 24-frames-per-second video at listed as "24Hz."
Interlaced scan Interlaced scan is a way to describe how some video signals and displays form an image. America's NTSC analog television system uses 525 scanning lines to create each complete picture (frame). The frame/picture is made up of two fields: The first field has 262.5 odd lines (1,3,5...) and the second field has 262.5 even lines (2,4,6...). The odd lines are scanned (drawn on the screen) in 1/60th of a second, and the even lines follow in the next 1/60th of a second. This presents a complete frame/picture of 525 lines in 1/30th of a second.
Analog NTSC video uses interlaced scanning, as do some digital television formats. Formats that include an "i" (1080i, 480i) use interlaced scanning. In fact, these days interlaced scanning is mostly mentioned when describing video broadcasts because virtually all non-tube TV types are progressive scan by nature. And for a more complete discussion of interlaced vs. progressive scan, see our article about HDTV resolution.
Internet-ready TV TVs labeled "Internet-ready" can connect to your home network to access online content. For example, a growing number of Internet-ready TVs let you play movies from services like Netflix®, BlockBuster™, or Amazon Video On Demand™. Keep in mind that you won't be able to browse the Internet the way you do on your computer — you'll only be able to access specific sites and information based on software included in your TV. Different TV makers provide access to different Internet sites and services, and sometimes these capabilities can be enhanced by firmware updates that the manufacturer provides. Besides movie services, common examples include weather, news, social media updates, and sports scores.
A few higher-end TVs have Wi-Fi® capability, but most TVs require a wired Ethernet connection. You can still get a wireless connection with many of those TVs by adding an optional USB Wi-Fi adapter. These adapters are usually brand-specific, so shop accordingly.
Keystone correction "Keystoning" is a form of video image distortion that occurs with front projectors if the centerline of the projector's lens is not perpendicular to the screen. Keystoning results in an image which is shaped like a trapezoid rather than a rectangle — the top of the picture is wider than the bottom, or the left side is taller than the right, for example. Most front projectors include "keystone correction" to correct this distortion. Some models have vertical keystone correction, while others include both vertical and horizontal correction. Although keystone correction allows greater mounting flexibility, it is a form of processing which usually has a slight softening and dimming effect on the picture.
LCD (Liquid Crystal Display) Liquid Crystal Display technology is one of the methods used to create flat-panel TVs. Light isn't created by the liquid crystals; a "backlight" behind the panel shines light through the display. The display consists of two polarizing transparent panels and a liquid crystal solution sandwiched in between. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal acts like a shutter, either allowing light to pass through or blocking the light. The pattern of transparent and dark crystals forms the image.
See our articles on flat-panel LCD technology and rear-projection LCD TVs for more details. There are also LCD-based projectors.
LCoS (Liquid Crystal on Silicon) A projection TV technology based on LCD. With LCoS, light is reflected from a mirror behind the LCD panel rather than passing through the panel. The control circuitry that switches the pixels on and off is embedded further down in the chip so it doesn't block the light, which improves brightness and contrast. This multilayered microdisplay design can be used in rear-projection TVs and projectors. TV makers use different names for their LCoS technologies — Sony uses SXRD™, while JVC uses D-ILA™ or HD-ILA™.
LED (Light Emitting Diode) An LED is a semiconductor diode that typically emits a single wavelength of light when an electric current passes through it. Different colors can be generated based on the material used; common colors include red, green, blue, and white.
White LEDs are used as backlights in some newer flat-panel LCD TVs, while colored LEDs are used in some recent DLP rear-projection TVs.
LED TV A term sometimes used for LCD TVs that use an LED backlight instead of a conventional fluorescent one. An LED backlight improves contrast and delivers a wider range of colors, for a more lifelike picture. TVs with LED backlights also generally consume less power than those that use fluorescent backlights.
Some of these TVs use a series of LEDs arranged in a grid behind the LCD panel. And some TVs with these LED grids feature "local dimming", which allows the TV to display light and dark portions of the same image more accurately. Other sets are "edge-lit," meaning that the LEDs are located around the sides of the panel instead of in a grid behind it. While edge-lit LED TVs don't offer local dimming, they generally have thinner cabinets — sometimes barely more than an inch deep. For more information, see our video on LCD backlighting.
Letterboxed video A method for displaying the entire picture as seen in a movie theater on a TV screen. The resulting image width is much greater than its height. On an old-fashioned TV screen with 4:3 aspect ratio, letterboxed videos appear with horizontal black bars above and below the image. You will often see these black bars when watching movies on a widescreen TV, too. To learn more about aspect ratios and ways to deal with those black bars, see our aspect ratio article.
Light output Measures the amount of light produced by a video display, and is an especially important spec for projectors. Expressed in "lumens" or "ANSI lumens," with a higher number indicating greater light output, which results in a brighter picture.
Local dimming A feature found on some LED-backlit TVs that allows them to dim or even completely shut off different sections of the LED grid independently. These TVs can accurately display both light and dark portions of an image at the same time, for greater contrast and a more lifelike picture.
Lumen The unit of measure for light output of a projector. Different manufacturers may rate their projectors' light output differently. "Peak lumens" is measured by illuminating an area of about 10% of the screen size in the center of the display. This measurement ignores the reduction in brightness at the sides and corners of the screen.
The more conservative "ANSI lumens" (American National Standards Institute) specification is made by dividing the screen into 9 blocks, taking a reading in the center of each, and averaging the readings. This number is usually 20-25% lower than the peak lumen measurement.
Luminance The brightness or black-and-white component of a color video signal. Determines the level of picture detail.
Megahertz (MHz) Equal to one million Hertz. Video signal bandwidth is typically expressed in megahertz.
Microdisplay A general term covering several different technologies used in digital rear-projection TVs and projectors. These displays produce large images; the "micro" refers to the postage stamp-sized image chips that create the images. Microdisplay types include DLP, LCD, and LCoS. For a comparison of rear-projection microdisplay types, and details on how each technology works, see our Choosing a Big-screen Projection TV article.
MPEG (Moving Picture Experts Group) The organization charged with developing video and audio encoding standards. On the video front, consumers are most likely to encounter the MPEG-2 and MPEG-4 compression formats, or "codecs." These formats are capable of producing very high quality video by employing an adaptive, variable bitrate process that can allocate more bits for complex scenes involving a lot of motion, while reducing the bits in static scenes.
· MPEG-2: Used for over-the-air digital television broadcasts, standard DVDs, some Blu-ray Disc and HD DVD discs, and small-dish satellite TV (DIRECTV and DISH).
· MPEG-4: This newer format is more efficient than MPEG-2, meaning it can deliver the same picture quality as MPEG-2 using a lower bitrate. Some Blu-ray Discs and HD DVDs, and newer DIRECTV and DISH satellite gear use MPEG-4.
NTSC (National Television System Committee) The North American 525-line analog broadcast TV standard, which was established over 50 years ago. Although it is referred to as a "525-line" standard, we're only able to see 480 lines on a TV display. The ATSC digital broadcast standard will replace NTSC as of June 12, 2009.
OLED (Organic Light Emitting Diode) OLED is an up-and-coming display technology that can be used to create flat-panel TV TVs. An OLED panel employs a series of organic thin films placed between two transparent electrodes. An electric current causes these films to produce a bright light. A thin-film transistor layer contains the circuitry to turn each individual pixel on and off to form an image. The organic process is called electrophosphorescence, which means the display is self-illuminating, requiring no backlight. OLED panels are thinner and lighter than current plasma or LCD HDTVs, and have lower power consumption. Only small OLED screens are available at this time, but larger screens should be available by 2009.
Overscan The portion of a video image that lies outside a TV's visible screen area. The amount of overscan varies from model to model, but typically ranges between 5% and 10% or the total image. Some recent TVs with "pixel-by-pixel" or "dot-by-dot" display modes are capable of showing the full image, with no overscan. This is especially advantageous when viewing 1080i or 1080p content on a 1080p TV.
Pan-and-scan The process of transferring a widescreen movie or other source material to videocassette, DVD, or broadcast so that it fits the squarish 4:3 aspect ratio of most old-fashioned TVs. This results in a significant amount of lost picture information, particularly in the width of the image. Most new HDTVs use the wider 16:9 aspect ratio, which can display all or most of the original picture of widescreen material.
At the beginning of a movie on videocassette, you'll usually see a disclaimer about the movie having been "...formatted to fit your TV." That means it's been converted to pan-and-scan.
Picture-in-picture (PIP) There are two flavors of picture-in-picture: 1-tuner PIP models require that you connect a VCR or other video component to provide the source for your second picture. 2-tuner PIP models have two built-in TV tuners, so you can watch two channels at once using only the TV.
Originally, PIP allowed viewing of multiple channels or sources by creating a small inset image overlaid on the main image. With the shift to widescreen displays, the inset type of PIP is gradually being replaced by "split screen" designs that are sometimes referred to as POP (picture-outside-picture) or PAP (picture-and-picture).
Pillar-boxed video The pillar-box effect occurs in widescreen 16:9 video displays when vertical black bars are placed at the sides of a non-widescreen 4:3 image. The smaller the size of the pixels in an image, the greater the resolution. To learn more about aspect ratios and ways to deal with black bars, see our aspect ratio article.
Pixel Short for "picture element." The smallest bit of data in a video image. As pixel size gets smaller, more pixels can fit in the same screen area, increasing picture resolution.
Pixel response time The amount of time it takes for a single pixel in a video display to switch from active to non-active; it is measured in milliseconds (ms). If a display's response time is too slow, faint motion trails may be visible following fast-moving on-screen objects. Pixel response time is an important performance spec for all types of digital flat-panel and projection displays although it's rarely listed for non-LCD TVs. For smooth, accurate playback of high-quality video material, look for a response time of 8 ms or less.
Plasma Plasma technology is one of the methods used to create flat-panel TVs. The display consists of two transparent glass panels with a thin layer of pixels sandwiched in between (think of this layer as containing somewhere between 800,000 and two million tiny fluorescent bulbs — the pixels). Each pixel is composed of three gas-filled cells or sub-pixels (one each for the red, green and blue primary colors). A grid of tiny electrodes applies an electric current to the individual cells, causing the gas to ionize. This ionized gas (plasma) emits high-frequency UV rays which stimulate the cells' phosphors, causing them to glow, which creates the TV image. For more info on how plasma technology works, see our LCD vs. Plasma article.
Progressive scan Some digital television broadcast formats (720p, 480p), and most DVD players, use a type of video signal known as progressive scan. Instead of splitting each video frame into two sequential fields like analog interlaced NTSC video, progressive-scan video displays the entire frame in a single sweep. For example, where standard NTSC video displays 30 frames (60 fields) per second, progressive scan displays 60 complete frames per second.
Another way to look at it is that progressive-scan video has twice as much picture information as the equivalent interlaced video format. Progressive-scan picture quality is more filmlike, with more fine detail and less flicker. Virtually all of today's digital TVs are progressive-scan displays, with screen resolutions of 720p, 768p or 1080p. For a more in-depth discussion of progressive vs. interlaced scan, see our article about video resolution.
Projector A video display device that projects a large image onto a physically separate screen. The projector is typically placed on a table, or ceiling-mounted. Projectors, sometimes referred to as front-projection systems, can display images up to 10 feet across, or larger. Old-fashioned large, expensive CRT-based projectors have been replaced by compact, lightweight, lower-cost digital projectors using DLP, LCD or LCoS technology.
QAM (Quadrature Amplitude Modulation) A digital modulation format used for downstream transmission in cable TV systems — commonly used for cable HDTV.
QAM tuner A QAM tuner allows cable subscribers to tune in unscrambled cable channels without a separate set-top box, including high-definition channels, if the cable service provider offers them.
Rainbow effect A visual artifact associated with single-chip DLP-based rear- and front-projection displays. Fortunately, only a few people see these momentary flashes of color, and fewer still find these "rainbows" to be distracting. For those unlucky few, rainbows typically occur when the viewer's eyes dart away from the screen. Rainbows result from DLP's use of a color wheel, which causes the three primary colors — red, green, and blue — to be projected sequentially, rather than continuously. Some recent single-chip DLP TVs have replaced the lamp-and-color-wheel system with colored LEDs, which reduce this effect. And rainbows aren't an issue for 3-chip DLP projectors because each primary color has its own dedicated image chip, so no color wheel is needed.
Rear-projection TV Typically referred to as "big-screen" TVs, these large-cabinet TVs generally have built-in screens measuring at least 40". Unlike the bulky CRT-based rear-projection TVs from years ago, today's "tabletop" rear-projection TVs are relatively slender and light. These TVs use digital microdisplay technologies like DLP, LCD, and LCoS. For an in-depth look at these new rear-projection TVs, see our Choosing a Big-screen Projection TV article.
Resolution In video terms, resolution refers to the amount of picture detail provided by a video signal or display. Although you may hear references to "lines of resolution," that's mainly a holdover from the tube-TV era. Today's digital TVs create their images using a grid of pixels; more pixels generally equals higher resolution. This grid has a fixed number of pixels, which means if the TV receives any video signal with a different resolution, the TV will scale that signal to fit the screen's pixels.
The picture quality you see on your TV depends on two factors: the resolution of the TV's screen and the resolution of the video signal. Since video images are always rectangle-shaped, there is both horizontal resolution and vertical resolution to consider.
· Vertical resolution: The number of horizontal lines (or pixels) that can be resolved from the top of an image to the bottom. (Think of hundreds of horizontal lines or dots stacked on top of one another.) The vertical resolution of the analog NTSC TV standard is 525 lines. But some lines are used to carry other data like closed-captioning text, test signals, etc., so we end up with about 480 lines in the final image. So, all of the typical NTSC sources — VHS VCRs, cable and over-the-air broadcast TV (analog), non-HD digital satellite TV, DVD players, camcorders, etc. — have vertical resolution of 480 lines. DTV (Digital Television) signals have vertical resolution that ranges from 480 pixels for SDTV, to 720 or 1080 pixels for true HDTV. If you're comparing TVs or video sources, vertical resolution is what's usually listed: 480p, 720p, 1080p, etc.
· Horizontal resolution: The number of vertical lines (or pixels) that can be resolved from one side of an image to the other. Horizontal resolution is a slightly trickier concept, at least for analog video, because while the vertical resolution of all analog video sources is the same (480 lines), the horizontal resolution varies according to the source. Some common examples: VHS VCRs (240 lines), analog TV broadcasts (330 lines), non-HDTV digital satellite TV (up to 380 lines), and DVD players (540 lines). DTV signals have horizontal resolution that ranges from 640 pixels for SDTV, to 1280 pixels (for 720p HDTV) or 1920 pixels (for 1080i and 1080p HDTV).
Multiplying the horizontal resolution by the vertical resolution gives you the total screen resolution. For example, a 1080p screen has 1920 horizontal pixels by 1080 vertical pixels — 1920 x 1080 = 2,073,600 pixels. For an in-depth look at high-definition video resolution, see our article about video resolution.
RF (radio frequency) jack Sometimes referred to as a "75-ohm coaxial" connection, this kind of jack is commonly used for bringing signals from antennas and other sources outside the home to components with some type of tuner, such as cable boxes, HDTV tuners, VCRs, satellite receivers, TVs, etc. A 75-ohm coaxial cable can carry video and stereo audio information simultaneously. However, as a way of making a video connection between components, RF is inferior to composite, S-video, component video, and HDMI. RF cable connectors (often called "F-type" connectors) either screw onto the 75-ohm jack, or just push on to connect. See our connections glossary for more info.
There are different types of coaxial cable. Standard coaxial cable is stamped "RG-59"; higher-quality "RG-6" cable features better shielding, and exhibits less high-frequency loss over longer runs. (For connecting DBS satellite systems, it's important to use RG-6 cable to correctly pass the entirety of the digital signal.)
Scaler Circuitry that converts a video signal to a resolution other than its original format. Scaling can involve upconversion or downconversion, and may also include a conversion between interlaced- and progressive-scan formats. A scaler can be built into a TV, HDTV tuner, DVD player, or home theater receiver, or may be a standalone component.
Scanning lines On CRT-based TVs, the number of scanning lines measures the screen's resolution. Scanning refers to an electron gun tracing horizontal lines across a phosphor-coated screen, painting each video frame as a series of lines. Although you may still hear the term "scan lines" used when describing digital TVs that use plasma, LCD, or other pixel-based technologies, it's not really accurate. These newer TV types flash each complete screen image simultaneously without any type of actual scanning.
SDTV (Standard-Definition Television) SDTV refers to the non-high-definition formats in the ATSC digital television standard. SDTV pictures can have either 4:3 or 16:9 aspect ratio. Picture and sound is clearer than analog NTSC video, with picture resolution of 480i or 480p. These digital signals require less bandwidth than analog signals, allowing TV stations to simultaneously broadcast multiple channels of programming in place of a single analog channel; this is called "multicasting."
Set-top box (STB) Also called converter boxes, these receivers convert broadcasts (either over-the-air broadcast HDTV, analog cable, digital cable, satellite, or Internet-based IPTV) for display on a television.
S-video Found on nearly all of the TVs we sell, this 4-pin connector usually provides a sharp, clear picture by transmitting the chrominance and luminance portions of a video signal separately. The signals can then be processed separately, reducing interference. Direct S-video connections generally outperform composite connections when hooking up video components like DVD players, DBS receivers, and S-VHS and Hi8 recorders and camcorders. However, they don't look as sharp as HD-capable connections like component video, and HDMI. See our connections glossary for more info.
SXRD™ — Silicon X-tal (Crystal) Reflective Display Sony's variation of LCoS projection display technology.
Tube TV See CRT.
Upconversion The term used to describe the conversion of a lower resolution to an apparently higher one. This process increases the number of pixels and/or frame rate and/or scanning format used to represent an image by interpolating existing pixels to create new ones at closer spacing.
V-Chip Several years ago the FCC (Federal Communications Commission) began requiring that TVs include "V-Chip" technology to block the display of television programs based on their rating. All sets with screens 13 inches or larger manufactured after January 1, 2000 must include the V-Chip. Broadcasters are required to encode an electronic signal in TV programs indicating the level of violence, language, and sexual content. Parents can program the TV with a rating so that when the the V-Chip reads a show's signal, it will prevent it from displaying if it is above the rating.
The rating system, known as "TV Parental Guidelines," was established by the National Association of Broadcasters, the National Cable Television Association and the Motion Picture Association of America. These ratings display on the TV screen for the first 15 seconds of rated programs.
Viewing angle Measures a video display's maximum usable viewing range from the center of the screen, with 180° being the theoretical maximum. Most often, the horizontal (side to side) viewing angle is listed, but sometimes both horizontal and vertical viewing angles are provided. For most home theater setups, horizontal viewing angle is more critical.
Widescreen When used to describe a TV, widescreen generally refers to an aspect ratio of 16:9, which is the optimum ratio for viewing anamorphic DVDs and HDTV broadcasts.
Wobulation A technique originally invented by Hewlett-Packard for its ink jet printers. Texas Instruments, developer of DLP display technology, employs wobulation in some of its image chips used in rear-projection TVs. Like interlacing, wobulation shows half the picture at a time, but displays the two halves so rapidly that our eyes combine the two parts into one. A 1080p DLP TV can display images with 1920 x 1080 pixels, yet its DMD (Digital Micromirror Device) image chip has 960 x 1080 mirrors. Half the image is displayed, then a separate pivoting reflective panel called an "actuator" shifts the display a half pixel's width to the side. This all happens fast enough to generate 60 full frames per second, for a clean progressive-scan image. Texas Instruments calls this technique SmoothPicture™, and it is also often referred to as "pixel-shifting."
x.v.Color (xvYCC color space) A high-definition video color space that is supported by many HDTVs beginning in 2007 (generally models with HDMI v1.3 inputs). The x.v.Color standard supports 1.8 times as many colors as the ATSC HDTV standard. Although there are HD camcorders that support x.v.Color, there are no broadcast or packaged consumer high-def sources that support it. Even if both your HDTV and high-def player support x.v.Color, your video source must be encoded with it as well or you won't see the wider color range.
