| Back Channel: |
A means of communication from users to content providers. Today, a simple type of back channel is an Internet connection using a modem.
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| Cable Modem: |
A data modem that uses the bandwidth of a given cable system. Because cable modems provide Internet access over cable, they are much faster than modems that use typical phone lines.
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| Cache: |
Storage of digital data (video, audio, text, etc.).
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Clone: |
An exact digital copy, indistinguishable from the original.
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Codec (Coder-decoder): |
A device that converts analog video and audio signals into a digital format for transmission. Also converts received digital signals back into analog format.
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| Data-casting:
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Enhanced options offered with some digital programming to provide additional program material or non-program related resources, allowing viewers the ability to download data (video, audio, text, graphics, maps, services) to specially equipped computers, cache boxes, set-top boxes or DTV receivers.
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Data Compression: |
A technique that provides for the transmission or storage, without noticeable information loss, of fewer data bits than were originally used when the data was created.
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| DDS: |
Digital Data Service. |
| DS: |
A tape format that is non-compressed component digital video which has provision for HDTV recording by use of about 4:1 compression (HD DS).
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Digital Disk Recorder (DDR): |
A video recording device that uses a hard disk drive or optical disk drive mechanism. Disk recorders offer nearly instantaneous access to recorded material.
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DING (Digital News Gathering): |
Electronic news gathering (ENG) using digital equipment.
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| DTV (Digital Television): |
This comprises all the components of digital television, including HDTV, SIDTV, data-casting and multicasting.
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| DVD (Digital Versatile Disk -- Formerly Digital Video Disk):
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Same size as a CD but stores seven times CD capacity on a single side. DVDs can also be double-sided or dual layer. Today most DVDs are used to display full-length commercial motion pictures, plus additional material such as outtakes, director's notes, movie trailers, etc.
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| DVTR: |
Digital videotape recorder. |
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Enhanced TV: |
Term 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. Also known as data-casting.
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| Enhancements: |
Producers add these options to some digital programming to enhance program material--enabling viewers to download related program resources to specially equipped computers, cache boxes, set-top boxes or DTV receivers.
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| 4:3: |
Aspect ratio of the NTSC TV screen, with "4" unit width corresponding to "3" unit height, proportionally, regardless of the actual size of the screen.
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| Grand Alliance: |
U.S. consortium, formed in 1993, to produce "the best of the best" DTV transmission system from among the initially proposed separate systems. Participants were: AT&T, General Instrument Corp., MIT, Philips Consumer Electronics, David Sarnoff Research Center, Thomson Consumer Electronics and Zenith Electronics Corp. The group eventually proposed the current ATSC digital standard.
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Interactive Television: |
TV programming with interactive content and enhancements, blending traditional TV viewing with the interactivity of a personal computer. |
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Letterbox: |
Image of a wide screen picture on a standard 4:3 aspect ratio television screen typically with black bars above and below. Used to maintain the original aspect ratio of the original source (usually a theatrical motion picture of 16:9 aspect ratio or wider).
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| Live-Streaming:
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Feeding (streaming) video/audio or other data to end-users at a specific time (that is, live). Today the term is most often used for online services.
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| NTSC: |
National Television Systems Committee and the name of the current analog transmission standard used in the U.S., which the committee created many decades ago.
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On-Demand Streaming: |
Sending video/audio or other data that is transmitted to the end-user upon request (widely used on news and sports-oriented Web sites, for example).
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| Sampling: |
Digital process by which analog information is measured, often millions of times per second, in order to convert analog to digital. |
| Simulcast: |
The broadcast of the same program simultaneously over two or more different systems or channels. An accelerated amount of simulcasting of both analog and digital programming will be required by FCC rules, during the DTV transition period.
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Terrestrial: |
A broadcast signal transmitted "over the air" to an antenna.
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| Widescreen: |
Term given to picture displays with a wider aspect ratio than NTSC 4:1 Digital HDTV is 16:9 widescreen. Most motion pictures also have a wide-screen aspect ratio, some even wider than 16:9. |
| Source: TV Trends, National Association of Television Program Executives |
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