A/V technical terms explained

There is a lot of stuff so I'll just split it in few posts.
Source is cnet asia site.

A to D

AC-3 - Audio coding 3 (see Dolby Digital).

ACATS - Advisory Committee on Advanced Television Service; special FCC committee that recommended DTV standards in 1997.

After color temp - Geek box term. The color temperature at a given brightness level after grayscale calibration. Usually expressed in degrees K; ideally as close to 6,500K as possible.

After grayscale variation - Geek box term. After calibration, the average amount of variation from an ideal of 6,500K, measured over the entire range of the grayscale--typically 20 to 100 IRE in 10-IRE increments.

ALiS - ALiS (alternate lighting of surfaces) technology developed by Fujitsu/Hitachi for plasma panel displays. On a conventional plasma TV, all pixels are illuminated at all times. With an ALiS plasma panel, alternate rows of pixels are illuminated so that half the panel's pixels are illuminated at any moment, somewhat similarly to interlaced scanning on a CRT-type TV. This allows higher native resolution than designs with discrete pixels (typically 1,024x1,024 versus 1,024x768 for 42-inch plasmas), but ALiS has historically suffered in other areas, including black-level performance.

Analog hole - A perceived chink in the armor protecting copyrighted content from unauthorized distribution--for example, over the Internet. Currently HDTV and other high-bandwidth content can be converted from analog to digital format and distributed widely. The MPAA wants to "plug" the analog hole by placing watermark detection capability in analog-to-digital converters (ADCs), which convert analog audio and video into digital form.

Anamorphic - Adopted from the film technique of shooting a wide-screen image on a square 35mm frame, it's the process of compressing wide-screen images to fit into the squarer standard 4:3 television signal. The images are then expanded for viewing in their original format on a wide-screen display device. Wide-screen or letterboxed DVDs that are not anamorphic have less detail when projected on a wide-screen monitor. In other words, a nonanamorphic wide-screen DVD is designed to be shown letterboxed on a standard "square" TV but appears with a black box all around the image when shown on a larger 16:9 wide-screen TV. To fill a 16:9 screen, a nonanamorphic DVD has to be blown up, resulting in loss of resolution and detail. Conversely, a DVD that is anamorphic, enhanced for 16:9, or enhanced for wide-screen delivers 33 percent more resolution than regular letterboxed transfers, is designed to be shown on a 16:9 TV, and does not need to be blown up. When one of these DVDs is shown on a "square" TV, it is often subject to anamorphic downconversion artifacts unless the TV has a vertical compression feature.

Anamorphic downconversion - Processing present in all DVD players that converts the image from an anamorphic DVD for display on a regular 4:3 TV. In the initial setup of a DVD player is a choice between a 16:9 or a 4:3 TV; the 4:3 options engage this processing, which often introduces artifacts such as jaggies and undulations during pans.

Anamorphic squeeze - See vertical compression.

ANSI - American National Standards Institute, a professional measurements and standards group.

ANSI lumens - Light-output specification set in 1993 used mainly to measure brightness of front-projection televisions; more exact than undefined lumens. The average 7-inch, CRT front-projection television is capable of between 150 and 175 ANSI lumens, while 9-inch CRT sets emit between 200 and 240. DLP and LCD projectors range from 600 to 7,000, depending on the model.

Artifact - Any abnormality in a video image; typically results from digital processing, the interlaced-scanning method, the conversion from one video format to another, or signal transmission issues.

Aspect ratio - The relationship between the width and height of an image; the standard DTV wide-screen ratio is 16:9 (1.78:1), as compared to the squarer NTSC ratio of 4:3 (1.33:1).

ATRC - Advanced Television Research Consortium, an organization of several large consumer electronics companies, research facilities, and broadcast entities that developed U.S. high-definition television (HDTV) standards.

ATSC - Advanced Television Systems Committee, a government-sanctioned, industry-led standard-setting body that adopted the official DTV standard for the United States in 1997. The acronym also refers to the DTV and HDTV standards.

ATVEF - Advanced Television Enhancement Forum, a coalition of broadcasters as well as hardware and software makers that created a standard for interactive data broadcasting, most of which would be broadcast as part of HD transmissions. These standards are currently under consideration by Society of Motion Picture and Television Engineers (SMPTE). The group discontinued operations on November 1, 2003.

Before color temp - Geek box term. The color temperature at a given brightness level before grayscale calibration. Usually expressed in degrees Kelvin; ideally as close to 6,500K as possible.

Before grayscale variation - Geek box term. Before calibration, using the television's best available presets, the average amount of variation from an ideal of 6,500K, measured over the entire range of the grayscale--typically 20 to 100 IRE in 10-IRE increments.

Bit rate - Typically measured in megabits per second (Mbps); used to express the rate at which data is transmitted or processed. For digital television, including digital satellite and cable TV, DVD and HDTV, the higher the bit rate, the more data that is processed and, typically, the higher the picture quality. The DVD format allows up to 9.8Mbps, while HDTV requires 19.25Mbps for full- bandwidth transmission.

Black level - The intensity of black in the television picture, frequently referred to as brightness; adjusted to compensate for ambient room light. Black level is set with a TV's brightness control using a PLUGE test pattern. Setting black level correctly is critical to overall picture quality, particularly the ability to see detail in dimly lit scenes of a movie. The term also refers to the ability of a display to produce an inky, deep black, which is often a problem in fixed-pixel displays.

Broadcast flag - Copy-protection scheme for over-the-air DTV broadcasts that restricts recording of "flagged" shows. Its function applies only to digital outputs on DTV devices, specifically DTV receivers, TVs, and PC-based DTV tuner cards. Forthcoming flag-compliant products will refuse to digitally output/transfer any flagged show to a nonflagged legacy device or software.

Blu-ray - Format for next-generation recordable HD DVD that uses a shorter-wave blue laser and is supported by most major DVD manufacturers. A single-sided, single-layer disc can hold 25GB of data.

Calibration - In televisions, the process of adjusting a picture to comply with standards used in DVD and HDTV production.

CEA - Consumer Electronics Association, the principal industry association for companies that manufacture consumer electronics.

CEDIA - Custom Electronics Design and Installation Association, the industry group for installers of home-theater, multizone audio, phone, security, lighting, and other home equipment.

Chrominance - Technical name for the TV signal that carries the color information (red, green, and blue) needed to produce a color picture; often called chroma.

Chrominance-to-luminance delay - Video artifact caused by the color signal lagging the brightness signal; appears as color smearing on the left edges of some onscreen objects; easiest to see with a test pattern that has a colored vertical stripe running down the middle of a white field.

Color decoder - Component in all televisions that translates color-signal information from the source for display on the TV. ATSC and NTSC require two separate decoder matrices. Practically speaking, many color decoders accentuate red to compensate for a blue color temperature, a phenomenon known as red push.

Color temperature - Sometimes called white balance and expressed in degrees kelvin or just Kelvins, this is the color of gray at different levels from black to white. Since color information overlays the black-and-white information in a TV signal, color temperature affects the entire range of color. The National Television Standards Committee (NTSC) standard is 6,500K, but typically manufacturers ship their TVs with color temperatures ranging from about 7,000K to 12,000K, on the blue side of the color spectrum, to make sets as bright as possible to stand out on a brightly lit showroom sales floor. Some sets have a selectable color temperature.

Comb filter - Component in all televisions that separates the chrominance and luminance from one another in composite-video connections. Good comb filtering enhances fine detail, cleans up image outlines, and eliminates most extraneous colors. Comb filters do not affect S-Video, component-video or digital-video connections.

Component video - The elements that make up a video signal, consisting of luminance and two separate chrominance signals, expressed either as Y R-Y B-Y or Y Pb Pr.

Composite video - Analog video signal that includes vertical and horizontal synchronizing information. Since both luminance and chrominance signals are encoded together, only a single connection wire or jack is needed.

Compression - Method of electronically reducing the number of bits required to store or transmit data. The method adopted for DTV is called MPEG-2. Four full-range channels of programming and data can be compressed into the same space required by a single analog channel.

Contrast ratio - Difference between the brightest whites and the darkest blacks a display can show. The higher the contrast ratio, the greater the ability to show subtle color details and tolerate ambient room light (for example). Most contrast-ratio specs reported by manufacturers are inflated.

CPTWG - Copy Protection Technical Working Group, a committee formed by consumer electronics and computer industry companies to recommend DVD and DTV copy-protection protocols.

CRT - cathode-ray tube, the original and still the most common display technology for televisions. Invented in 1897 by German physicist Karl Ferdinand Braun, the tube uses an electron beam to scan lines on the screen. It does not have an exact resolution as a fixed-pixel display does.

DC restoration - Geek box term. Measurement of how well a television is able to maintain a consistent color of black regardless of the brightness of the rest of the image.

Defeatable edge enhancement - Geek box term. Ability of a TV to not introduce any extra edge enhancement.

Deinterlacer - See line-doubler/tripler/multiplier.

Digital Cable Ready - Official term for an HDTV that conforms to the plug-and-play digital cable TV standard using POD (point of deployment) access cards, also called CableCARDs. With cable systems that comply to the standard, users can plug the cable directly into an HDTV set, then enjoy HDTV and digital cable without having to use a separate set-top box. Sets with interactive functionality are labeled Interactive Digital Cable Ready.

Digital comb filter - Device that separates the luminance and chrominance parts of a video signal in the digital domain, which provides enhanced color purity and reduced dot crawl over the analog variety. See comb filter

Direct view - Any television not based on projection technology. Most often refers to standard CRT televisions, as opposed to rear- or front-projection TVs.

Divx - Digital Video Express. Defunct pay-per-view DVD feature that played back both standard and lower-cost DVDs; Divx-enhanced DVD players had to be connected to a phone line to track additional viewings of discs but was discontinued by its primary promoter, Circuit City, in June 1999. Divx is not to be confused with DivX video format.

DivX - MPEG-4-based compressed digital video format (or codec) used for Internet distribution of movies; often called the MP3 of video. DivX Networks is the name of the company that sells DivX content and is not to be confused with Circuit City's defunct Divx DVD format.

DLP - Digital light processing. A microdisplay technology invented by Texas Instruments, DLP is based on a digital micromirror device (DMD), a chip with millions of hinged, microscopic mirrors attached, each of which corresponds to a single pixel in the projected image. Red, green, and blue light filtered through a color wheel is directed alternately onto the DMD, which switches on and off up to 5,000 times a second. The reflected light is directed through a lens and onto a screen, creating an image. High-end HDTV projectors use a three-chip solution, with separate DMDs for green, red, and blue, and forego the color wheel.

Dolby Digital - Six-channel digital audio standard that is part of the U.S. digital television standard; also called AC-3 or Digital 5.1. The channels consist of front left, front right, front center, surround or rear left, surround or rear right, and a separate subwoofer (the .1).

Downconvert - In DTV, the conversion from a higher-resolution input signal number to a lower one. For example, some DTV receivers can be set to downconvert an HDTV 1080i signal to a standard 480i signal that any TV can display.

DRM - Digital Rights Management. General term that describes a variety of technical and/or legislative efforts for securing and protecting different forms of digital content for the benefit of copyright holders.

DTCP - Digital Transmission Copy Protection. HDTV copy-protection scheme more commonly called 5C.

DTLA - Digital Transmission Licensing Administrator. The licensing organization for the 5C DTCP HDTV copy-protection technology.

DTV - Digital television. Generic term that refers to all digital television formats, including high-definition television (HDTV) and standard-definition television (SDTV).

D-VHS - Digital-VHS. Version of VHS (Video Home System) videocassette standard capable of recording HDTV via a FireWire connection; D-VHS decks are made by JVC and Mitsubishi.

DVI - Digital visual interface. Omnidirectional digital connectivity standard that conveys an uncompressed digital signal from a digital source, such as an ATSC tuner, to a display. HDCP copy protection is often used in conjunction with the DVI connection. DVI connections do not carry audio.

DVR - Digital video recorder. A television recorder such as Replay and TiVo that uses a hard drive, an EPG, and internal processing to drastically simplify programmed recording and playback of recorded programs. A DVR vastly increases recording time compared to VCRs or DVD-recording decks; often enables smart programming, in which the device records an entire series or programming defined by keywords, genre, or personnel; and offers pause control over "live" broadcasts. Also called personal video recorder (PVR) or hard disk video recorder.

E to K

EIA-775 - Specific consumer electronics industry IEEE 1394 digital video cable standard; also called FireWire.

Edge enhancement - Generic term for artificial edges created around onscreen objects. With already-sharp, high-resolution sources such as DVD and HDTV, it actually obscures detail and increases noise. Scan-velocity modulation circuits, a TV's sharpness control, or the source itself (such as a DVD) are some possible sources of edge enhancement.

EDTV - Enhanced Definition Television (see 480p). Also used to describe plasma and other fixed-pixel displays that have 852x480 resolution. They can show an HDTV image but don't provide as much detail as higher-resolution displays.

EPG - Electronic program guide. Feature found on satellite and cable tuner boxes and DVRs, and increasingly on TVs and DVD recorders, that provides an onscreen listing of available channels and program data for an extended time period (typically 36 hours or more).

False contouring - An artifact common to fixed-pixel displays that produces splotchy, distinct sections in what should be gradual gradations of color or shadows. Also referred to as solarization and posterization.

FireWire - Bidirectional high-speed digital video/audio and data interface technology adopted by the Institute of Electrical and Electronics Engineers (IEEE). Unlike other video connectivity standards, FireWire requires software programming to ensure compatibility between devices; the FireWire jack on most DVD recorders, for instance, is programmed to be compatible only when connected to a digital camcorder. FireWire connections between HDTV devices, such as a digital cable box and an HDTV recorder, are controlled by 5C DTCP copy-protection technology. FireWire is Apple Computer's version of the IEEE 1394 interface and is now administered by a consortium that includes Apple and several other companies; sometimes referred to as i.Link (Sony's name), DISH Wire (by Echostar), and EIA-775.

Fixed-pixel display - Digital televisions that use discrete pixels to create a picture image, such as plasma, LCD, DLP, LCoS, or any non-CRT display device. In the case of DLP, for instance, each pixel is represented by one of the hundreds of thousands of tiny mirrors mounted on a DLP chip.

Flat-panel TV - Video display typically using gas plasma or LCD technology and that measures only a few inches thick.

Footlambert - Measurement of light emitted or reflected from a perfectly diffused surface; used to rate brightness in projection TV sets; the higher the rating, the brighter the picture. One footlambert is equal to the relative reflected light radiated by one candle over a one-square-foot area. This measurement is often misleading and misused on projector spec sheets.

Fps - Frames per second. The number of individual still pictures that pass by every second to create a moving image. Film runs at 24fps, while video, including DVD, runs at 30fps. To compensate for the difference, 2:3 pull-down detection is used.

Front projection - Type of TV system in which the picture is projected onto a reflective screen or even a wall. The larger the picture, the more visible the pixels or scan lines and the darker the image. CRT systems use three tubes (red, blue, and green), whereas LCD and DLP uses a single projection lens.

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.

Geek box - CNET's way of providing at-a-glance Labs results for TV reviews.

Geometric distortion - Unnatural bowing of straight lines or other distortion of shapes, especially at the sides and corners in a TV picture.

Geometric linearity - Ability of a television to reproduce lines, shapes, and sizes accurately.

Ghosting - Multiple overlaid TV images noticeable around the edges of objects; occurs when an antenna picks up the original TV signal along with duplicate signals reflected by tall buildings and other similar obstacles. DTV broadcasts can suffer from ghosting, which is sometimes called multipath.

Grayscale - Range of gray at different intensities from completely black to completely white. Since color information is overlaid atop black-and-white information in a composite, S-Video, and component-video signal, the ideal is to set the entire range of the grayscale as close to the standard of 6,500K as possible to preserve color fidelity.

Grayscale variation - Geek box term. The average variation above or below 6,500K, measured on the grayscale from 20 to 100 IRE in 10-IRE increments.

HDCP - High-bandwidth Digital Content Protection. Copy-protection scheme developed by Intel to be used in conjunction with DVI and HDMI connections.

HDMI - High-Definition Multimedia Interface. USB-like digital video connectivity standard designed as a successor to DVI; can transmit both uncompressed digital audio and video signals; protected by HDCP digital copy protection.

HD-DVD - High-definition digital video disc. Several formats have been proposed for these high-capacity DVDs, including Blu-ray.

HDTV - High-definition television. High-resolution digital television broadcast and playback system composed of roughly a million or more pixels, 16:9 aspect-ratio screens, and AC3 digital audio. A subset of digital television, HDTV formats include 1080i and 720p resolution.

HDTV-ready - Used to describe any TV that can display high-definition formats when connected to a separate HDTV tuner or source. These TVs generally have built-in tuners for receiving regular NTSC broadcasts, but not ATSC digital broadcasts. The CEA's official term for an HDTV-ready TV is HDTV monitor.

HDTV monitor - Official CEA term for HDTV-ready.

HDTV tuner - See DTV tuner

Horizontal resolution - Number of vertical lines (or pixels) that can be resolved from one side of an image to the other. While the vertical resolution of all analog video sources is the same (480 lines), the horizontal resolution varies according to the source. Some examples for typical sources: 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 lines for SDTV to 1,280 lines (for 720p HDTV) or 1,920 lines (for 1080i HDTV).

IEEE 1394 - Institute of Electrical and Electronics Engineers 1394. Official designation of the FireWire digital connectivity standard.

Independent input memories - Feature found on newer TVs that automatically associates a separate picture memory slot--usually including contrast, brightness, sharpness, color, tint, and color temperature--with each input. Greatly eases optimization of picture parameters specifically for different devices.

Integrated HDTV tuner - The terrestrial ATSC high-definition tuner built into an HDTV, it allows the set to receive over-the-air HDTV broadcasts without having to attach a set-top box.

Interactive Digital Cable Ready - See Digital Cable Ready.

Interlaced scanning - Scan method used by the majority of televisions and the 1080i HDTV format. As opposed to progressive scanning in which the CRT's electron beam scans or "paints" all lines at once, interlaced scanning TVs paint odd-numbered lines in succession, then go back and fill in the remaining even-numbered lines. This method is more prone to artifacts and less stable than progressive.

IRE - International Radio Engineers. In calibration, used to refer to different brightness levels on the grayscale. 20 IRE is quite dark, while 100 IRE is extremely bright.

Jaggie - Type of video artifact that looks like a jagged edge as opposed to a smooth line. It often appears on diagonal lines in 30fps material.

Kelvin (K) - In TV, unit of measurement used to describe the color of light produced by the screen.

Keystone correction - Feature found in front projectors designed to compensate for mounting situations when the centerline of the projector's lens is not perpendicular to the screen. Although keystone correction allows greater mounting flexibility, it almost always reduces apparent resolution and makes the image dimmer.

L to R

LCD - Liquid-crystal display. System used on many DTVs, clocks, answering machines, handheld organizers, camcorders, and personal computers. Liquid crystals are sandwiched between two glass plates. Minor temperature variations are introduced to particular points in the display using pinpoint electric charges, illuminating or causing the crystals to change colors in predetermined patterns.

LCD TV - A television that employs a liquid-crystal display screen rather than a CRT; used in small, personal TVs, portable video equipment, front projectors, and larger flat-panel displays. An LCD projector uses a lamp to shine light through liquid-crystal panels, then through mirrors and lenses to the screen.

LCoS - Liquid Crystal on Silicon. Whereas LCDs uses liquid crystals sandwiched between two glass plates, this newer hybrid projection TV technology employs liquid crystals coated on a silicon chip, which results in easier, lower-cost manufacturing and higher-resolution images.

Letterbox - A wide-screen movie on DVD, laserdisc, or videotape presented in its original theatrical wide-screen width on a standard square 4:3 TV. The film is shown with black bars above and below the picture area to create the wider, theatrical image. Often used to indicate a non anamorphic DVD.

line-doubler/tripler/multiplier - Technology used in televisions to create a higher-quality picture by increasing the number of lines of resolution displayed; it can be a separate device or a feature built-in TVs, primarily DTVs. A poor-quality line-doubler can actually degrade the image from lower-resolution analog or digital signals.

Lumens - The unit of measure for the light output of a projector. Different manufacturers may rate their projectors' light output differently, and these numbers are usually inflated. "Peak lumens" is measured by illuminating an area of about 10 percent 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. See also ANSI lumens

Luminance - Portion of a television transmission that controls brightness of the red, green, and blue proportions in a television picture. The standard luminance setting in a picture is 30 percent red, 60 percent green, and 10 percent blue. These numbers are adjusted to produce varying colors, grays, whites, and blacks.

Mbps - Megabits per second. The standard unit of bit rate measurements, it represents 1,024 kilobits or 1,048,576 bits per second, although in practice this number is often rounded to 1,000,000 bits.

Microdisplay - Type of fixed-pixel projection television that uses a chip illuminated by a lamp to produce the image--as opposed to projection technologies that use CRTs. Examples include DLP, LCD, and LCoS rear-projection HDTVs.

MPAA - Motion Picture Association of America. Industry association for producers of motion pictures.

MPEG - Moving Pictures Experts Group. Pronounced EM-peg, this group establishes standards in computerized digital video compression and reproduction.

MPEG-2 - Moving Picture Experts Group-2. Video-compression scheme used to condense digital video content for broadcast over thin TV bandwidths or via the Internet, and to squeeze full-length digital films onto a DVD.

MPEG-4 - Advanced compression scheme finalized October 1998, designed to enable transmission and reception of high-quality audio and video over the Internet and next-generation mobile telephones; potentially enables mobile video phones, video e-mail, and cordless video cameras. Two major versions are MPEG-4 Simple Profile for low-resolution digital video content, usually for distribution over the Internet, and MPEG-4 AVC (Advanced Video Coding), which offers faster and higher-quality compression than MPEG-2 for HDTV content.

Native resolution - The resolution at which a TV or monitor is designed to display images. Image signals higher or lower than a specified native resolution must be converted to be displayed accurately. For example, a TV with a native resolution of 1080i can display 1080i images but may upconvert 480p images to 1080i. In contrast, a TV with a native resolution of 480p must downconvert a 1080i signal to 480p for display. CRT-based projection TVs can have more than one native resolution, but fixed-pixel displays such as LCD and DLP are limited to display one resolution and convert all others.

NTSC - National Television Standards Committee, the FCC engineering group formed in 1940 to develop technical standards for black-and-white television (NTSC broadcasting began July 1, 1941) and color television (1953). NTSC is also the video-transmission standard used in the western hemisphere, Japan, and other Asian countries. NTSC standards are 525 lines of resolution transmitted within a 6MHz channel at 30fps.

Overscan - Geek box term. The amount of picture area that gets cropped off along the edges of a television screen. Zero percent overscan means the television does not crop off any of the incoming picture. Overscan is often set intentionally at the factory to be 5 percent, or even higher along the edges, to ensure the screen is full at all times regardless of fluctuations in brightness (which can change the overall picture size) or nonstandard signals, such as those from camcorders or video games.

PAL - Phase Alternating Line. This video-transmission standard was introduced in the early 1960s and is used in most European countries except France and the former Soviet Union. PAL standards specify 625 lines of resolution at 50fps.

Pan-and-scan - Process of transferring a movie or other source material to videocassette, DVD, or broadcast so that it fits the 4:3 aspect ratio of most current TVs. This results in a significant amount of lost picture information, particularly in the width of the image, and sometimes involves panning unnaturally across the frame. At the beginning of a movie, there is often a disclaimer about the movie having been "...formatted to fit your TV." That means it's been converted to pan-and-scan. See also anamorphic.

Pixel - Dots of color, sometimes composed of separate red, green, and blue subpixels, that combine to create an image; from the words picture element.

PLUGE - Picture Line-Up Generation Equipment. Test pattern for video equipment to set black level.

Plasma - Display technology used in large-screen, flat-panel TVs. Each plasma panel contains thousands of tiny tubes that are like miniature fluorescent lights, filled by ionized gas in a plasma state. When excited by electricity, the tubes--which are backed by red, green, or blue phosphors--glow in different colors and intensities to create an image.

Progressive scanning - Also called sequential scanning, this is the antithesis of interlaced scanning used in broadcast television, the process by which all odd and even scanning lines are "painted" by an electron beam every 1/60 of a second. This method reduces flicker and increases stability.

PVP - Personal video player. Portable device designed to play back video files from a hard drive; may or may not include a small LCD screen.

PVR - Personal video recorder. See DVR.

QAM - Quadrature Amplitude Modulation. Type of digital cable tuner.

Rainbow effects - A potential problem with DLP-based displays characterized by brief streaks of color, especially in fast-moving scenes. The occurrence of these rainbows can be significantly reduced with newer and faster color wheels.

Raster - On a CRT television, the overall area scanned by the electron guns.

Rear projection - TV system where the picture is projected onto the rear of a translucent screen via a series of mirrors and viewed as you would an average television.

Red push - Tendency of the color decoder in many TVs to accentuate the color of red compared to blue and green. Red push is typically introduced intentionally to compensate for an overly blue color temperature.

Resolution - The sharpness of a video image, signal or display, generally described either in terms of lines of resolution, or pixels. Visible resolution depends on both the resolution of the display and the resolution of the video signal. Since video images are always rectangle-shaped, they are described with both horizontal and vertical resolution.

RF jack - Radio frequency jack. Audio/video connection commonly used to bring signals from antennas, cable systems, and satellite dishes to components with some type of tuner, such as cable boxes, cable modems, HDTV set-top boxes, VCRs, satellite receivers, TVs, and so on. It can carry video and stereo-audio information simultaneously. When used to connect two components, such as a VCR and a TV, RF provides the lowest video quality of any connection. RF cable connectors usually screw or push onto the jack. Also called F-type, 75-ohm, or coaxial connections.

S to Z

Scaler - Circuitry or device 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 progressive- and interlaced-scan formats. A scaler can be built into a TV, an HDTV set-top box, a DVD player, or another video source, or it may be a standalone component.

Scan velocity modulation - TV feature; a circuit that increases the speed of electrons to their respective phosphor dots. Often produces an artificial "hard edge," which is why it should be switched off for sources such as DVD and HDTV. Used in professional projectors as a form of dithering to reduce the visibility of scan lines. Also called velocity scan modulation or, generically, edge enhancement.

SDTV - Standard-definition television. Digital television format that includes 480-line resolution in both interlaced (480i) and progressively scanned (480p) formats; offers discernible improvement over conventional analog NTSC picture resolution, with less noise; similar to DVD or satellite TV quality but not considered high-definition television (HDTV).

SECAM - Système Électronique Couleur Avec Memoire, or sequential color with memory. Analog color television broadcast standard developed in the mid-1960s and used in France, its former possessions, and some eastern European countries, including former members of the Soviet Union; offers 819 lines of horizontal resolution.

Selectable aspect ratios - TV feature, especially on a wide-screen and/or digital model, that allows the adjustment of screen proportions for the material being viewed; an image can be adjusted to fill the screen or to have blank bands placed at the top and bottom of a wide-screen image, or the left and right for a 4:3 image on a wide-screen set.

Selectable color temperature - Large-screen TV feature, especially a high-end set, that allows the adjustment of the color temperature.

Service menu - Menu in televisions and some other electronics gear that's normally accessible only by inputting a special code. The service menu controls many parameters that, if changed, could permanently damage the product, and damage of this kind is usually not covered by the manufacturers' warranty.

Set-top box (STB) - External receiver that converts broadcasts (such as analog cable, digital cable, or DTV) for display on a television. HDTV-ready TVs must be connected to a compatible HDTV tuner set-top box in order to receive digital television programs.

Sidebars - See windowbox bars.

SMPTE - Society of Motion Picture and Television Engineers, a professional engineering organization that reviews technological advancements and sets professional video standards.

Solarization - See false contouring.

Spatial artifact - A compression-induced DTV image imperfection that occurs in a single field or frame when an image on screen is not translated accurately; often results in fuzzy or slanted edges, often on text. Similar to temporal artifacts, both often referred to as mosquito noise.

S-Video -Common video connection that provides better picture than composite by transmitting the luminance and chrominance portions of a video signal separately.

SVM - See scan velocity modulation.

Temporal artifact - In a digital video image, a picture imperfection that occurs over several frames, often in smooth-textured areas and around high-contrast edges of moving video objects. Similar to spatial artifacts, both often referred to as mosquito noise.

Temporal resolution - One of two possible ways to measure resolution in a video image; the other is spatial. Describes the amount of picture detail in a moving image, measured by the number of lines of resolution delivered over a given period of time. When an image moves rapidly, a 720p HDTV display will provide more picture information than a 1080i HDTV display because progressive scan produces twice as many frames in the same period of time as 1080i.

Terrestrial broadcast - Standard over-the-air broadcasts, as opposed to satellite or cable transmission.

Upconvert - In DTV, the conversion from a lower-resolution input signal to a TV capable of displaying higher resolutions, such as from an SDTV 480p signal to an HDTV 1080i native display.

Velocity scan modulation - See scan velocity modulation.

Vertical compression - Feature found on 4:3 TVs designed to take advantage of the extra resolution in anamorphic DVDs and other wide-screen content. Pioneered by Sony, this feature squeezes the TV raster so that the electron beam scans in a smaller area. It requires setting the DVD player to 16:9 mode, eliminates anamorphic downconversion artifacts, and ideally provides a 33 percent increase in resolution in the letterboxed image.

Vertical frequency - In television, the number of vertical fields per second measured in hertz. NTSC has a vertical frequency of 60Hz, whereas PAL has 50Hz.

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. Some lines are used to carry other data such as closed-captioning text, test signals, and so on, so we end up with about 480 lines in the final image. All of the typical NTSC sources, including VHS VCRs, cable, and over-the-air broadcast TV (analog), non-HD digital satellite TV, DVD players, camcorders, and so forth, have a vertical resolution of 480 lines. DTV signals have vertical resolution that ranges from 480 lines for SDTV, to 720 or 1,080 lines for HDTV.

VSB - Vestigial sideband. A type of digital television transmission technology; the U.S. DTV standard uses 8VSB.

White-field uniformity - The evenness of a field of white across a television screen.

Wide-screen - Image with an aspect ratio greater than 1.33:1 or a picture wider and narrower than a standard television image. Typically refers to TVs in the 16:9 aspect ratio.

Windowbox bars - The blank bars on the left and right of a 4:3 image when displayed on a wide-screen 16:9 display. They can often be adjusted in intensity from black to gray; gray bars help exercise CRT and plasma displays more evenly across the screen.

Y Pb Pr - Luminance, two chrominance channels of blue minus luminance, red minus luminance. Technical shorthand for component video.

Y Cb Cr - Luminance, two chrominance channels of blue minus luminance, red minus luminance. Technical shorthand for component video.

Y R-Y B-Y - Luminance, two chrominance channels of red minus luminance, blue minus luminance. Technical shorthand for component video.