Digital Televison Glossary

Analog TV: Analog technology has been in use for the past 50 years to transmit conventional TV signals to consumers. "Standard" television broadcasts in analog TV. Analog signals vary continuously, creating fluctuations in color and brightness.

Aspect Ratio: 4:3 is the aspect ratio of analog television, while 16:9 is known as widescreen and closely approximates how most films are shown in a movie theater. The numbers represent units wide by units high. A 16:9 widescreen is 16 units wide by 9 units high. Watching movies in the widescreen when your TV is set for 16:9 nearly eliminates the black bars at the top and bottom of the picture. However, programs broadcast in analog will show up in the 4:3 ratio, even if your HDTV is set at 16:9, leaving black sidebars on each side of the picture. These can be eliminated by stretching the 4:3 picture so that it fits the 16:9 screen.

ATSC: An acronym for advanced television systems committee, and the name of the DTV system used by broadcasters in the U.S.

Barn Doors: A term used in television production to describe the effect that occurs when a 4:3 image is viewed on a 16:9 screen. When this happens, viewers see black bars on the sides of the screen or "barn doors."

Codec: This term is short for "Coder-decoder." A codec is a device that converts analog video and audio signals into a digital format for transmission. It also converts received digital signals back into an analog format.

Compression: Compression refers to the reduction of the size of digital data files by removing redundant and/or non-critical information. Compression allows a vast amount of data-to be transmitted in a relatively small amount of spectrum. A high-definition television signal requires 1.5 gigabits of data. In the United States, the DTV signal is reduced to 194 million bits per second! To put this into perspective, the phone line to a home handles 28,000 bits per second.

Computer Input: Some HDTV sets have an input like SVGA or VGA that allows the TV sets to be connected to computers.

Datacasting: Also known as "enhanced TV." Datacasting is the act of providing enhanced options offered with some digital programming to provide additional program material or non-program related resources. This allows viewers the ability to download data (video, audio, text, graphics, maps, services, etc.) to specially equipped computers, cache boxes, set-top boxes, or DTV receivers.

Decoder: See "codec." A device or program that translates encoded data into its original format (i.e., it decodes the data.)

Digital: Digital refers to the circuitry in which data-carrying signals are restricted to one of two voltage levels, corresponding to logic 1 or 0.

Digital Cable: A service provided by many cable providers, digital cable offers viewers more channels. Contrary to many consumers' beliefs, digital cable is not the same as High-Definition Television or digital television; rather digital cable simply offers cable subscribers the options of paying for more services. Digital Monitor: DTV monitors are televisions that can display a digital signal but lack an integrated tuner (unlike an integrated digital set), and thus cannot receive a digital broadcast signal without an additional set-top box.

Digital Monitor: DTV monitors are televisions that can display a digital signal but lack an integrated tuner (unlike an integrated digital set), and thus cannot receive a digital broadcast signal without an additional set-top box.

Digital Television (DTV): Digital TV is the umbrella term encompassing High-definition Television and several other applications, including Standard Definition Televison, datacasting, multicasting and interactivity.

Digital Tuner: A digital tuner serves as the decoder required to receive and display digital broadcasts. It can be included inside TV sets or via a set-top box.

Direct View CRT: The least expensive option when considering purchasing a high-definition television. They utilize traditional cathode-ray (CRT) technology that powers standard analog TV sets, and as a result, are quite big and bulky-some units weigh 300 pounds or more. Their relatively low prices make direct view displays popular with consumers, but they will fall out of favor as the prices of the more sleek plasma and LCD displays continue to decline.

Dolby Digital: This is a digital surround sound technology used in movie theaters and upscale home theater systems that enhances audio. Home theater components with this technology work in conjunction with a "5.1-speaker" system (five speakers plus a low-frequency subwoofer) to produce true-to-life audio that draws the listener into the onscreen action.

Down Converting: Process by which a high-definition signal is converted to a standard definition picture.

Enhanced TV: Also known as "datacasting." This term is used for certain digital on-air programming that includes additional resources downloaded to viewers. Some forms of enhanced TV allow live interaction; other forms are not visible on-screen until later recalled by viewers. Producers add these options to some digital programming to enhance program material -- allowing viewers the ability to download related program resources to specially equipped computers, cache boxes, set-top boxes, or DTV receivers.

Enhanced definition TV (EDTV): Enhanced definiton TV cans receive any digital signal, but can only output signals at 480p, which is better quality than analog, but not nearly as high quality as high-definition, which is broadcast in either 1080i or 720p.

Generation Loss: This refers to video degradation caused by successive recordings (dubs of other dubs) from the master source. This is overcome by digital recording.

HDTV: "High-definition Television." This is the most superior video picture available in Digital TV. In the U.S., the 1080i and 720p formats in a 16:9 aspect ratio are the two acceptable HDTV formats. HDTV is a component of DTV.

HDTV Ready TV: Term used by some advertising to indicate an analog tv with display capability to become an hdtv with the addition of an hdtv tuner.

HDTV Monitor: Any monitor (display) with the inputs and capability to become an hdtv with the addition of an hdtv tuner.

HDTV Tuner: (also decoder, receiver, set-top box): A standalone device capable of receiving and outputting hdtv signals.

Interactive Television: This is when TV programming features interactive content and enhancements, blending traditional TV viewing with the interactivity of a personal computer.

Interoperability: This refers to the ability of a system or a product to work with other systems or products without special effort on the part of the customer. For example, interoperability would be required for a digital television set to be plugged into a VCR that is plugged into cable with all the components working together.

Interlaced Scanning: This process divides and presents each video frame as two fields. Imagine a video frame being divided by the odd and even horizontal lines that make up the picture. The first field presents the odd lines; the second field represents the even lines. The fields are aligned and timed so that, with a still image, the human eye blends the two fields together and sees them as one. Motion in the image makes the fields noticeable. Interlace scanning allows only half the lines to be transmitted and presented at any given moment.

Letterbox: Letterbox refers to the image of a wide-screen picture on a standard 4:3 aspect ratio television screen, typically with black bars above and below. It is used to maintain the original aspect ratio of the original source (usually a theatrical motion picture of 16:9 aspect ratio or wider).

Liquid Crystal Display (LCD): LCD flat panels use the same technology behind many computer monitors in which light is projected through a layer of liquid crystals and then colorized, producing the on-screen image. Until the last few months, LCD TVs were only available in relatively small sizes compared to plasma and rear-projection sets. Some major LCD manufacturers have recently introduced larger screen sizes.

Multicasting: The option to multicast was made possible by digital technology to allow each digital broadcast station to split its bit stream into 2, 3, 4 or more individual channels of programming and/or data services. (For example, on channel 7, you could watch 7-1, 7-2, 7-3 or 7-4.)

Must-carry: This refers to the legal obligation of cable companies to carry analog or digital signals of over-the-air local broadcasters.

NTSC: NTSC is the acronym that stands for National Television Systems Committee"and the name of the current analog transmission standard used in the U.S., which the committee created in 1953.

Pixel: Pixel is actually two words jammed together ? picture and element. A pixel is a tiny sample of video information, the "little squares" that make up an overall picture.

Pixels Per Inch: Pixels per inch (PPI) is a measure of the sharpness (that is, the density of illuminated points) on a television display screen.

Plasma Screen: Plasma displays get their name from the gas that is trapped inside each of the roughly two million pixels that are contained in an HDTV unit. Plasmas are popular due to their elegance and flatness, as they can be as small as three inches thick. However, they are also quite expensive, ranging in price from $2,500 up to $15,000 or more.

Plug-and-Play or Digital Cable Ready: A DTV or other device that plugs directly into the cable jack and does not require a separate set-top box. Plug and Play TV owners must obtain a cable card from their cable company in order to view scrambled programming services.

Progressive Scanning: A system of video scanning where lines of a picture are displayed consecutively (unlike interlaced).

Rear Projection Set: Rear-projection HDTVs are produced by a variety of technologies, including cathode-ray tube (CRT), digital light processing (DLP), liquid crystal display (LCD) and liquid crystal on silicon (LcoS).

Rear Projection CRT: Their displays are available in large sizes (up to 70 inches) and are popular due to their relatively low prices as compared with plasma or LCD. However, they are quite bulky?with some units being nearly 3 feet deep?and can be difficult to view when sitting angled from the TV.

Rear Projection DLP: Digital light processing displays are based on microchip technology from Texas Instruments. DLPs have better picture quality than rear projection CRT, not as expensive as plasma or LCD flat panel, essentially immune to burn-in, excellent brightness levels, great picture quality. They are more expensive that rear-projection CRT and can suffer from a ?rainbow effect.?

Rear Projection LCD: Liquid crystal display sets are based on the same LCD technology that powers the more expensive LCD flat panel models, but with the size and costs advantages of rear-projection. They have better picture quality than rear-projection CRT, not as expensive as plasma or LCD flat panel, much less bulky than rear-projection CRT and essentially immune to burn-in.

Rear Projection LcoS: Rear Projection LcoS (liquid crystal on silicon) is a new technology that is poised for growth due in large measure to chipmaking giant Intel's announcement that it is entering the market for production of LcoS chips. Several manufacturers are in production on 1080p versions of rear-projection LcoS that will be the first to display the full capability of HDTV. The rear projection LcoS sets have much higher resolution and picture quality than rear-projection CRT. They are less bulky than rear-projection CRT and not as expensive as plasma or LCD flat panel. They are much more expensive than rear-projection CRT.

Resolution: The level of resolution directly affects picture quality. The higher the resolution, the more picture detail there is. Many things affect picture quality, including number of bits, pixel count, format, receiver quality, cameras, lenses and lighting used for live or taped programming. Resolution is measured by the number of pixels displayed. One of the high-definition picture formats is composed of 1080 active lines, and each line is composed of 1920 active pixels. Therefore, each frame has over 2 million (1080x1920=2,073,600) color pixels creating the image. By way of contrast, today's typical analog television is roughly equivalent to 480 active lines, with each line holding about 440 pixels. So, each frame has a little over 200,000 color pixels in use creating the image.

Sampling: This is the digital process by which analog information is measured, often millions of times per second, in order to convert analog to digital.

Standard Definition TV Format (SDTV): There are two main digital formats - HDTV and SDTV. SDTV typically does produce better quality images than that of traditional analog TV and pictures somewhat akin to digital cable. However, its images are not nearly as sharp as the images from the ultimate form of digital television ? High-definition TV (HDTV).

Set-top Converter Box: This unit sits on top of the viewer's analog TV, receives the Digital TV signal, converts it to an analog signal, and then sends that signal on to the analog TV.

SVGA: This acronym is short for the "Super Video Graphics Array" display mode. SVGA resolution is 800 x 600 pixels.

Terrestrial Broadcasting: This is a broadcast signal transmitted "over-the-air" to an antenna.

Thick-film dielectric electroluminescent technology (TDEL): A flat panel TV technology that consists of a series of flat layers that includes a phosphor layer and a dielectric film sandwiched between two layers of electrodes.

Upconverting: Process by which a standard definition picture is changed to a simulated high-definition picture.

VGA: This acronym is short for the "Video Graphics Array" display mode. VGA resolution is 640 x 480 pixels.

Wide screen: A term given to picture displays with a wider aspect ratio than NTSC 4:3. Digital HDTV or SDTV is referred to as "16:9 wide screen." Most motion pictures also have a 16:9 wide screen aspect ratio. Most Digital TVs have a screen that is wider than it is tall (if a Digital TV screen is nine inches high, it's 16 inches wide.) When watching a show recorded in the wide screen format on a Digital TV, viewers see more of the movie, while when viewing wide screen format on an analog TV, cropped edges are evident.