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Digital TV Glossary

Select the first letter of a glossary term to jump to the section of the list starting with that letter:


1394 The standard for a digital connection or bus used to transfer data between two independent systems. The 1394a standard provides 400-Mbps bandwidth and the reach is limited to 3 or 4 meters. The 1394b standard extends the bandwidth to 800 Mbps and the reach to a whole-house environment.   1080i Type of high-definition television (HDTV) image that is 1,080 vertical lines by 1,920 horizontal pixels wide, displayed in an interlaced format. (It has a 16:9 aspect ratio, 29.97 Hz frame rate, as defined by the Advanced Television Systems Committee (ATSC) standard.)

720p Type of high-definition television (HDTV) image that is 720 vertical lines by 1,280 horizontal pixels wide, displayed in progressive format. (It has a 16:9 aspect ratio, 59.94 Hz, 29.97 Hz, and 23.98 Hz frame rates, as defined by the ATSC standard.)   480p High-definition television (HDTV) image that is 480 vertical lines by 720 horizontal pixels displayed in progressive format (It has a 4:3 or 16:9 aspect ratio, 59.94 Hz, 29.97 Hz, and 23.98 Hz frame rates, as defined by the ATSC standard.)

480i Type of standard digital television (SDTV) image that is 480 lines by 720 pixels wide, displayed in interlaced format. (It has a 4:3 or 16:9 aspect ratio, 29.97-Hz frame rate, as defined by the ATSC standard.)      


Analog A type of waveform signal that contains information such as image, voice, and data. Analog signals have unpredictable height (amplitude) and width (frequency) and can vary infinitely over a given range.   Aspect ratio

Ratio between the width and height of the video image. Standard National Television System Committee (NTSC), phase-alternation line (PAL), Advanced Television Systems Committee (ATSC) (standard definition) and digital video broadcasting (DVB) (standard definition) use a 4:3 ratio; ATSC and DVB high-definition formats use a 16:9 format.

Asynchronous serial interface (ASI) Transmission standard defined by the digital video broadcast (DVB) used to connect video delivery equipment within a cable, satellite, or terrestrial plant.   Advanced Television Systems Committee (ATSC)

Committee established by the FCC to define new standards for publicly regulated broadcast television in the United States.

Advanced Television Enhancement Forum (ATVEF) A standard for combining intellectual property (IP) data with television video.    


B frame An MPEG-2 compressed video frame derived by extrapolation between previous and future frames.   Bandwidth A measure of the capacity of a circuit or channel -- the amount of information transferred between points within a specified time period.

Broadband Term that generally refers to high-bandwith capacity. Broadband has a multi-channel capacity that is greater than or equal to 45 Mbps (US standard) or 34 Mbps (European/international standard).      
Conditional access (CA) A cryptographic technique for controlling which receivers are able to access a particular signal.   Coded orthogonal frequency division multiplexing (COFDM) The modulation scheme selected by the DVB committee for digital terrestrial broadcast television. (See Modulation.)

Compression A mathematical method of reducing the amount of digital information needed to re-create a television picture or frame.   Content protection (CP) Cryptographic and design techniques used to limit how data flows within a receiving device and between devices. This is generally used to restrict copying of copyright-protected material.
Datacasting Jargon referring to the propagation of information from one source to another source.   Demodulation A method for extracting digital information stored in a specific pattern on a radio frequency (RF) signal.

Digital Information sent as a series of high (1) and low (0) signals separated by a fixed period of time.   Discrete Cosine Transform (DCT) A step used in the MPEG coding process to convert data from spatial to temporal domain.

Digital light projection (DLP) A technique developed by Texas Instruments that creates a video image on a piece of silicon and uses mirrors and light to project the image onto a viewable screen.   Digital satellite service (DSS) MPEG-2-based digital transmission format (e.g., DirectTV).

Digital set-top-box (DSTB) A device that receives and decodes digital video broadcasts for consumer viewing.   Digital television (DTV) A device that receives, decodes, and displays digital video broadcasts (in both high-definition and standard-definition formats) for consumer viewing.

Digital video broadcast (DVB) MPEG-2-based digital television standard that defines formats for cable, satellite, and terrestrial broadcast.      
Encryption A mathematical technique for scrambling information such that only those with a key piece of information can unscramble the information to recreate the original message.   Enhanced television Any of several techniques for providing a viewer with additional information associated with a television program or advertisement.
Federal Communications Commission (FCC) The U.S. government body responsible for setting and enforcing regulations of transmissions over publicly accessible airwaves.   Frame The lines and columns of pixels that make up the displayed image. Video speed, expressed as frames per second (FPS), gives the rate at which the video image is updated.
High-definition television (HDTV) High-definition video formats that have 16:9 aspect ratio. Generally refers to 1080i or 720p images.   Hypertext markup language (HTML) Standard text format used for Internet documents.
I frame An MPEG-2-compressed video frame containing most of the original information. Used as a reference to build subsequent B and P frames.   Inverse discrete cosine transform (IDCT) A step in the MPEG decoding process to convert data from temporal back to spatial domain.

Interactive television A capability in DTV or DSTB that allows a user to control the action of the television and view the results of his/her action on the television.   Interlaced A scanning technique in a video system where odd and even horizontal lines of a video frame are displayed during alternating update cycles. Lines 1, 3, 5, etc., are displayed during the first cycle, creating one field. Lines 2, 4, 6, etc., are displayed on the second cycle, creating the next field. Two fields combine to make one frame.
Macrovision A copy-protection scheme that inhibits illegal copying of analog television programs. Macrovision Corporation developed and licenses the technology.   Modulation A technique for embedding digital information in a radio carrier wave for broadcast.

Motion compensation (MC) A step in the MPEG-2 video decompression (decoding) process.   MPEG-2 A digital video and audio compression (encoding) technique defined by the Moving Pictures Expert Group (MPEG).

Multicasting Generally, multicasting refers to propagation from one source to only a subset of potential destinations. It also means a technique for simultaneously sending multiple DTV programs on a single channel. The frequency used to carry a single analog television program can be used to carry up to six digital programs.      
National Television System Committee (NTSC) The committee that decided on the compatible color television system for the US. The FCC adopted it in 1953.    
Phase-alternating line (PAL) The analog color video composite system developed in Europe and used by countries around the world. It is similar to the NTSC standard, but it uses a sub-carrier phase alternation technique that makes certain kinds of transmission errors appear to cancel.   P frame An MPEG-2 compressed video frame containing original information and information derived from previous frames.

Pixel The smallest unit of color in a display. Frames are made up of lines and columns of pixels. The number of pixel lines in each frame expresses video resolution.   Plasma display panel (PDP) Flat panel display using plasma electronic technology.

Pay-per-view (PPV) A technique of controlling television access whereby the customer is charged on the basis of what programs he/she watches.   Progressive A picture-scanning process where all the lines of the image are scanned by every vertical scan.
Quadrature amplitude modulation (QAM) A modulation method used by cable DTV that combines changes in phase and amplitude to send four bits with each baud.   Quadrature phase shift keying (QPSK) A modulation method used by satellite DTV that transmits information by varying the phase of a sine wave.
Radio frequency (RF) Refers to the use of radio carrier waves to transmit a broadcast signal. (See "Modulation".)   Red, green, blue (RGB) The basic color signals used to drive a display.

Redundant array of independent disks (RAID) Used to store video programming in video production and delivery environments.      
Serial data transport interface (SDTI) Transmission standard defined by the Society of Motion Picture and Television Engineers (SMPTE) to transmit compressed digital video using serial digital video interface (SDI) connections.   Serial digital video interface (SDI) Transmission standard defined by SMPTE which is used to connect video production equipment to transfer SD video at 270, 360, or 540 Mbps and HD video at 1.485 Gbps.

Society of Motion Picture and Television Engineers (SMPTE) Forum that defines standards for television and film production.   Standard definition television (SDTV) Standard definition video format that has 4:3 aspect ratio. Generally refers to 480i.
Terrestrial television Television signals broadcast from local radio towers. Homes with antennas capable of picking up the broadcast signals are able to receive the television program.   Transport Stream (TS) Data stream that includes ancillary data, compressed video, and compressed audio.
Universal serial bus (USB) A digital connection between two separate electronic devices which provides "plug-and-play" capability.      
Video on demand (VOD) The viewer pays a small fee to the television service provider in order to watch particular movies listed on the on-screen television menu. Similar to pay-per-view.   Vestigial sideband (VSB) Modulation scheme selected by the US Advanced Television Systems Committee (ATSC) for digital terrestrial broadcast television.



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