HomeHome
- Afterdown Glossary (powerful)
- Home Theater Glossary
- Chi Mei Technical terms
- SAMPO support glossary
- Audio sound.com - HDTV Glossaries A-D / E-K / L-Z
- Projector/LCD-TV glossary
- DVD Glossary
- Technik-Lexikon - in German language
- EMI/EMC Glossary * http://www.dare.nl/engels/glossary.htm
- Video Compression Glossary * http://www.bmrc.berkeley.edu/projects/mpeg/faq/mpeggloss.html
- ILC Glossary of Internet Terms * http://www.matisse.net/files/glossary.html
DVB glossary API Application Programming Interface ATM Asynchronous Transfer Mode BPSK Binary Phase Shift Keying CA Condition Access CATV Community Antenna TeleVision CSA Common Scrambling Algorithm DAVIC Digital Audio VIsual Council DECT Digital Enhanced Cordless Telecommunications DSM-CC Digital Storage Media Command Control D-SNG Digital Satellite News Gathering DVB Digital Video Broadcasting DVD Digital Video (or Versatile) Disk DVC Digital Video Cassette D-VHS Digital - Video Home System SFDMA Synchronous Frequency Division Multiple Access GSM Global System for Mobile communication HDTV High Definition TeleVision HFC Hybrid Fibre Coax IEC International Electrotechnical Commission IRD Integrated Receiver Decoder ISO International Organization for Standardization IS Interactive Service ISDN Integrated Services Digital Network LMDS Local Multipoint Distribution System LNB Low Noise Block (down converter) MMDS Microwave Multipoint Distribution System MPEG Moving Picture Experts Group MultiCrypt Is used to describe the simultaneous operation of several CA systems. MVDS Multipoint Video Distribution System OSI Open Systems Interconnection PCM/CIA Personal Computer Memory / Card International Association PDH Plesiochronous Digital Hierarchy PSTN Public Switched Telephone Network SDH Synchronous Digital Hierarchy SAS Subscriber Authorization System SFN Single Frequency Network SI Service Information SMATV Satellite Master Antenna TeleVision SMS Subscriber Management System SimulCrypt A process that facilitates using several Conditional Access (CA) systems in parallel, in conjunction with the DVB common scrambling algorithm, to control access to pay-TV services. SimulCrypt involves the inter-operation o two or more CA streams in a DVB environment. DVB SimulCrypt addresses specifically the requirements for interoperability between to or more CA systems at a head-end (see TR 101 197 [38]). TS Transport Stream TV TeleVision PES Programme Elementary Stream VSAT Very Small Aperture (satellite) Terminal VHS Video Home System
Glossary of Networking and Telecommunication Terms
ABR (Available Bit Rate) A lower priority ATM traffic class of service negotiates for whatever bandwidth is available. ATM (Asynchronous Transfer Mode) An international packet switching standard using a cell-switched approach, in which each packet of information features a uniform size of 53 bytes (digital words of eight bits each). Of the total cell, 48 bytes is the "payload," or information to be transmitted. Five bytes are used as a "header," providing all the addressing information for that particular packet. ATM could switch and route information of all types, including video, voice and data. Asynchronous A method of sending data over a communications line by Transmission placing a block of transmitted bits in an "envelope." The envelope begins with a "start" bit that tells a computer a character is beginning. The "stop" bit sends a message that a character has ended. Asynchronous transmission also has the advantage of not needing precise clocking mechanisms that maintain a time relationship between transmitter and receiver. Baud Frequently confused with "bits per second (BPS)," baud is the number of times a state change occurs on a communications channel per second. A 2400-baud modem changes its signals 2400 times a second. The baud rate equals BPS only when a state change represents a single bit of data. BER (Bit Error Rate)A measure of transmission accuracy. It is the ratio of bits received in error to bits sent. BISDN (Broadband Integrated Services Digital Network)A high speed ISDN service intended to support full motion video and image applications, as well as data, at speeds of approximately 150 Mbps. Bit/Byte A bit is the most basic element of digital information. One bit-represented by either a 0 or 1, the absence or presence of electricity or light-is combined with other bits to form an eight-bit word or Byte. Bytes are the words of our digital language. Depending on how the bits within them are ordered, these bytes can be translated into numbers, words or commands. Bit Rate The speed at which digital signals are transmitted, expressed in bits per second. BRI (Basic Rate Interface) This ISDN scheme is identified as 2B+D, and permits two "bearer" channels, each operating at 64 Kbps, and one "data" channel, operating at 16 Kbps, to be carried over a single twisted pair copper wire. Broadband Any communications system able to deliver multiple channels or services of video, voice, or data to its users or subscribers over a broad band of RF spectrum. CAP (Competitive Access Provider) An Alternative carrier that competes with telephone companies in carrying traffic. CBR (Continuous Bit Rate) A higher priority ATM traffic type that guarantees that a sustained traffic rate is guaranteed across the network CCITT (Comitre Consultatif Internationale de Telegraphique et Telephonique) An international group operating under the auspices of the International Telecommunications Union (ITU) and charged with establishing telecommunications standards. Name recently changed to ITU-TSS (International Telecommunications Union-Telecommunications Standards Sector). CDMA (Code Division Multiple Access) A transmission scheme used by some cellular carriers. Derived from spread spectrum techniques used by the military. Claimed to be more efficient than other systems and to offer up to 20 times more call handling capacity than analog cellular systems. Cell Relay A packet switching technique that uses cells of uniform length. Cell relay is well suited to video transmissions, where the predictable arrival of packets in proper order is important. Central Office The telephone company facility housing the switches and other equipment that provide telephone service for customers in an immediate geographical area. Circuit Switching The type of signal switching traditionally used by telephone companies to create a physical connection between a caller and a called party. Client-Server A distributed computing architecture in which numerous dispersed terminals, each of which has its own central processor and memory, communicate with centralized processing, storage and output resources. In a client-server network, the client is a front end resource for a user, while the server represents the back end set of resources. Servers include devices such as mainframe computers, mini-computers, personal computers, hard disk and other types of memory devices. Clients typically are personal computers. Client-server also is a concept used by software programs running on distributed computing platforms. In a cable TV context, a client is a set-top terminal or other intelligent device at a customer premises. CPE (Customer Premises Equipment) The telecommunications equipment located on a customer's premises. Usually refers to key systems, private branch exchanges (PBXs), telephones, etc. DLC (Digital Loop Carrier) A digital transmission system designed for subscribers loop plant. Multiplexes a plurality of circuits onto very few wires or onto a single fiber pair. Ethernet A data communications protocol operating at up to 10Mbps. ESP (Enhanced Service Provider) The FCC defines enhanced services as "services offered over common carriers transmission facilities....which employ computer processing applications that act on the format, content, code, protocol...." Therefore an enhanced service provider operates, in one way or another, on the information being transmitted. FDDI (Fiber Distributed Data Interface) A standard designed to allow traffic of up to 100Mbps to be transmitted in a local area network. FITL (Fiber In The Loop) Used generally to refer to the deployment of fiber between the central office and the subscriber. Fiber Optic The rapid transmission of light pulses in a coded digital format through the fiber cable. In a fiber optic transmitter, a light source such as a laser or light-emitting diode (LED) is connected to the fiber cable. This light source converts an electronic input signal into a series of light pulses (representing bits) by blinking on and off millions of times per second. This stream of light pulses is the combination of many lower rate bit streams formed using digital multiplexing techniques. At the other end of the fiber, fiber optics receivers capture the light pulses for conversion to electrical signals. Frame Relay A data transmission technique similar to the X.25 protocol that features the use of a "flag" as a start bit, an address to indicate intended destination of the message, the actual payload to be delivered, an error detection sequence and a flag indicating end of the packet. Gbps (Giga Bits Per Second) Giga is the prefix representing 109 or one billion. For example, 10Gbps means 10 billion bits per second. Headend Control center of a cable TV systems. HFC (Hybrid Fiber Coax) The telephone industry term for a broadband network using standard cable TV transmission components such as optical transmitters and receivers, coaxial cable, amplifiers and power supplies. A cable TV technologist might refer to the same network as a "fiber-to-the-feeder" (FTTF) or "fiber-to-the-serving area" (FSA) network of "fiber-to-the-neighborhood". A common definition for a network featuring optical fiber from a central office/headend location to a neighborhood of 500 homes. In some cases, the neighborhood serving area can range from 48 to several hundred homes. HFC has the ability to replace the existing twisted-pair telephone network, offering all services over a single physical infrastructure. ISDN (Integrated Services Digital Network) In its simplest form, called Basic rate ISDN, it provides a means of transmitting two voice channels (each operating at 64 Kbps) and one data channel (operating at 16 Kbps) over a single pair of twisted copper conductors. The two voice channels are called bearer, or" B" channels; the single data channel is the "D" channel. A more complex form of ISDN is called Primary rate ISDN; in this system there are 23 "B" channels operating at 64 Kbps and one "D" channel operating at 64 Kbps. Thus the transmission capability of Basic rate is 144 Kbps, and that of Primary rate ISDN at 1.5 Mbps. IDLC (Integrated Digital Loop Carrier) A Digital Loop Carrier System that connects directly to a central office switch. Kbps (Kilo Bits Per Second) Kilo is the prefix representing 10, or one thousand. For Example, 384Kbps means 384,000 bits per second. LAN (Local Area Network) A limited distance network connecting a defined set of terminals. It could connect workstations within an office, offices in a building or buildings within a campus, etc. LATA (Local Access Transport Area) The geographic area that is the domain of the local exchange and carrier. Bell operating companies are generally precluded from carrying traffic across LATA boundaries; this traffic must be handed off to an interexchange carrier. Local Loop The portion of the telecommunications network that connects a subscriber's phone or business' PBX to the local central office. Also known as " the last mile". Mbps (Mega Bits Per Second) Mega is the prefix representing 106 or one million. For example, 10Mbps means 10 million bits per second. MPEG (Motion Picture Experts Group) An international standards-setting group working under the supervision of the International Standards Organization (ISO) and the International Electrotechnical Commission, MPEG's mission is to develop standards for compressed full-motion video, still image, audio and other associated information. The MPEG effort primarily is concerned with requirements for coding and decoding the video and audio, storing and transporting the video. Multimedia Multimedia is the integration of at least two of five information types for presentation on a television, desktop computer screen, personal information manager or other computer-driven device with a screen interface. Multimedia information can include text, still graphics, animation, audio, full-motion video or still photos. Multiplexer Equipment that permits simultaneous transmission of multiple signals over one circuit. NGDLC (Next Generation Digital Loop Carrier) Commonly used acronym for Integrated Digital Loop Carrier (See IDLC) Packet A bundle of data packaged for transmission over a network. Packets can be various lengths, ranging from about 40 bytes up to 32,000 bytes on the Internet, but typically about 1,500 bytes in length. The Asynchronous Transfer Mode, a new standard for switching data of various types over private and public networks, specifies a packet of uniform 53 byte length. Protocol A set of rules about how computers are to act when talking to each other. The protocols, such as Ethernet, IEEE 802.5 token ring, X Modem or Kermit. QOS (Quality of Service) A contracted data rate that is negotiated between two ATM end points that guarantees throughput and data delivery. Synchronous A method of sending information over a transmission Transmission line and separating discrete characters and symbols by a precise separation in time. Synchronous transmission offers higher throughput because it does not require the start-stop bits used by asynchronous methods. Synchronous transmission is more expensive, however. VBR (Variable Bit Rate) An ATM traffic class of service that is typically of secondary priority. In VBR, the peak and sustained cell rates can be reduced through negotiation. WAN (Wide Area Network) An integrated data network linking metropolitan or local networks over common carrier facilities
16x9 Anamorphic. Used to differentiate a 16x9 widescreen picture which fills the whole frame, from a 16x9 letterbox with blank lines at the top and bottom of the frame. The Americans don't understand anemorphic in the context of television - their equivalent term is 16x9 full frame.
API. Application Programme Interface is the definition of the form of computer software and data (an Application) which provides the EPG and interactive functions in the digital receiver.
Applets - Programs written using the Java language and linked to document much like images.
ATM stands for Asynchronous Transfer Mode and is a method that is taking the telecom industry by storm for splitting digital audio, video or data signals into little data packets, which can all be fed together into ginormous bitstreams and, with luck, reach their right addresses and can be put back together in the right order.
Bouquet Association Table - an optional element of SI which provides a means of pointing to associated services on other multiplexes
CA Conditional Access. A means of allowing system usrs to access only those services which are authorised to them.
Centre Cutout - One of the ways of viewing with an existing 4x3 television and a set-top box. The 4x3 patch is taken from the middle of the 16x9 image, unless the broadcaster has programmed pan-vectors, and there is considerable cropping of the image at the sides. The alternative is to switch the set-top box to a 16x9 letterbox display.
Common Interface Connection for plug-in computer card in the receiver, designed to carry the conditional access subsystem. Its proposed use also includes plug-ins for audio description and much, much more.
Control Word The secret key used for a scrambling algorithm.
Copy Protection A system which allows live viewing of movies and other programmes but prohibits back-to-back copying. Particularly important in the new digital era since the quality of recordings is indistinguishable from the original. The system to be used is called Macrovision.
Digital Audio Video Council - is a worldwide association of bodies concerned to promote interoperability in audio visual equipment of all kinds concentrating on standardised interfaces. A major focus of their work has been an API for the set-top box and the DAVIC 1.3 API consists of an MHEG5 content decoder with an additional cut down Java virtual machine.
DCT Stands for Discrete Cosine Transform and is the technique for getting at the redundancy which is in television images in order to reduce the datarate.
DigiTAG - is the European equivalent of DTG in the UK, being a consortium of broadcasters and manufacturers working on common standards within the DVB framework with the objective of achieving a European wide market for receiver designs. Digitag operates under the auspices of the EBU. More information from their website, http://www.digitag.org/
DMux Group - the name given to meetings of the four terrestrial multiplex operators, BBC, Digital3&4, SDN and BDB. They have recently tried to rebrand themselves as The Digital Network but, in industry circles at least, old habits are proving hard to break!
DSM-CC Digital Storage Media, Command and Control. The DVB defined method adopted for UK DTT for transmitting object carousel messages.
DTG The Digital Television Group. THE association of interested parties committed to launching digital services in the UK who's website you are now enjoying!
DVD Digital Video Disk - the new CD standard recording 4.7GBytes giving 140 minutes at an average of around 3Mb/sec, but with a peak capability of 8Mb/sec. It is this that we will be compared to.
Dynamic Multiplexing. Variation of datarate programme by programme so as to allow simultaneous transmission of other services. Involves a calculated risk that shots within the programme will not exceed the allowed datarate (See also Statistical Multiplexing)
ECM - Entitlement Control Message is a component of the electronic key system (sometimes called the Multisession Key) and is transmitted encrypted to control the descrambling process. Its use has been perverted(?) by some satellite operators to carry specific programme pricing information. Jokingly said also to stand for Electronic Counter Measures
EMM - Entitlement Management Message or Unit Secret Key it authorises specific decoders to decrypt the broadcast service, programme-by-programme if required.
EPG. Electronic Programme Guide. The new flashy name for that part of what teletext currently does. In digital, it is possible to make the images a lot smarter than teletext.
ESG Electronic Service Guide. The ESG is a basic navigation system resident in the receiver or set-top unit which uses programme schedule supplied by broadcasters in open SI. As such it is non-proprietry.
ETSI. The European Telecommunications Standards Institute, the body responsible for technical standards in television in Europe, which stands below the world standards authority ITU.
Event Information Table - part of the SI which is used to transmit information about events (programmes) in the MPEG transport stream. The DVB mandate the transmission of details about the present and following events for the multiplex concerned; the ITC mandate the transmission of present-and-following for the other five terrestrial multiplexes; beyond that it is optional whether to use the EIT to provide comprehensive listings (ESG) or to transmit an EPG as privately defined data.
FireWire. Serial digital bus connector for interconnecting domestic units, ultimately likely to replace the function of the SCART socket in analogue. The proper name for FireWire is IEE P1394 High Performance Serial Bus. P1394 has been chosen by the DVB Multimedia Home Platform Committee for interconnection of digital equipments in the future home-area network. P1394 defines the physical layer - the transport layer is likely to be ATM
Hotspot. a box or other object on the screen that the viewer can interact with.
HTML. Hypertext Mark-up Language (HTML) is the language of the web. It consists of blocks of text and images with embedded instructions on how it is to be presented by the browser. What makes it exciting is the ability to embed hypertext links to other HTML files, either on the same site or anywhere on the web. These URLs take the form of http://www .... The standards for HTML are under the control of the Wordwide Web Consortium (W3C), an open standards making body representing all companies with interests in web development. What makes HTML of interest to digital television is the amount of content which is being created in HTML. Creating content costs money and costs can be amortised by reusing or reversioning content for Internet use, for CD-ROMs and for digital television. HTML based information could permit truly local news on digital television, could allow advertisers to link adverts to more information for use by interested viewers, etc.
Impulse Purchase. Method allowing viewer to make spur-of-the-moment decision to purchase pay-per-view programmes, download services and home shopping on credit, which is subsequently signalled back to the SMS for invoicing.
IRD. Integrated Receiver Decoder Beware terms - integrated does not mean that the box is part of the display unit! Usually the term is now reserved for professional equipments used at cable head-ends etc.
Java - is an object oriented programming language developed by Sun Microsystems which is designed to be small, simple and portable across platforms and operating systems. It has come to prominance as an extention to HTML coding for the Internet. A cut-down version, dubbed personal Java, has great attractions as the virtual machine for the digital set-top box. and forms part of nearly all developments by API suppliers.
Joint Stereo. A coding option in MPEG for exploiting the redundancy between left and right audio channels and transmitting at 192kb/sec. However, research suggest that this is not adequate when Dolby encoded surround sound is transmitted. As broadcasters don't alwaysreliably know when feature films are Dolby encoded, it may be safer to transmit everything as separate stereo at 256kb/sec.
JPEG stands for Joint Picture Expert Group, which preceded MPEG. It dealt only with still pictures but the standard was adapted and adopted widely for moving images - so called Motion JPEG. The snag is that one manufacturers Motion JPEG decoder probably wont read anothers signal correctly.
Letterbox - a television picure with blank lines at the top and bottom giving a wider aspect ratio.
MHEG-5 - In the argument over APIs, it is often said we should adopt HTML as so much content is mastered in HTML. However, HTML is designed for a different purpose and fundamentally does not allow the placement of text and objects on the screen in a predictable way. MHEG-5, the core of the DAVIC API, does the job properly (and can take HTML as its source). DAVIC V1.3 (though not the Java virtual machine) has been adopted by the terrestrial multiplex operators as the UK "Content Decoder."
MPEG-2 Stands for Motion Picture Expert Group, which designed the family of standards that all digital broadcasting, CDi and CD-ROM moving images employ.
Multiplex A uhf channel used to carry digital signals. By means of compression, several services can be carried in the same channel. How many is the hot question.
Navigation The process by which the viewer is able to find wanted programmes in the multi-channel situation
Near Video on Demand Technique used in digital Satellite and Cable services using several channels to transmit a feature film with staggered start times.
Network Information Table - one of the four mandatory Service Information tables transmitted with every digital broadcast to identify itself.
Now-and-Next. Slang for the present and following events in an EIT.
OFDM Orthogonal Frequency Division Multiplex, is the method of taking thousands of tiny carriers to convey digital signals in a spectrum that is already full of analogue ones. The equivalent method of modulation for satellite broadcasting is QPSK and for cable is 64QAM.
OSD On Screen Display. OSD memory is the RAM which produces it.
Pause Point - a natural break in presentation where the aspect ratio can be switched without serious breakup or digital artifact. Black is best but it may be possible to switch on a still frame when the MPEG decoder buffer will be relatively empty.
PPV Pay-Per-View. Alternative to subscription regarded by many to be the new source of income of the future, but essentially requires a return path. Unfortunately, the number of "big" events is limited and may be more applicable to small charges for early viewing of soaps, repeats etc. In this situation, rather than entitle individual IRDs, it may be better to download credit to the smartcard and deduct from that as a local transaction, which is subsequently signalled to the SMS overnight. (Also see Impulse Purchase)
PCMCIA is the connector which is proposed for the common interface CA module.
Running Status Table - there is no requirement that the now-and-next EIT is synchronised with programme junctions. The RST is an optional element of SI which can be used, for example, to start a vcr.
Safe Area - a reduced area of the picture which should contain important action and graphics may be placed without fear of cutoff. With mixed 4x3 and 16x9 viewing, what is safe is a debatable point!
Scrambling. The process of making a signal unintelligible such that it can only be received if an authorised descrambling system is available in the receiver.
Service Description Table - one of the four mandatory SI tables which lists the names and parameters of each service referred to.
Service ID - a unique identifier of a service within a transport stream and part of the SDT
Signing. There are 70,000 deaf people in the UK who use sign language. The Broadcasting Act 1996 requires the signing of 1% of all programmes (15 mins per day) within 1 year of launch. This must increase to 5% within 10 years. Signing is defined in British Sign Language (BSL) but there are variations which can cause confusion. Amongst recognised authorities is Ben Steiner, Lecturer for Deaf Studies at Wolverhampton University.
SFN. Single Frequency Network - a way of broadcasting from a grid of transmitters using only one frequency. Restrictions on transmitter spacing make it inappropriate for the UK.
Shoot and Protect - the buzz-word which describes framing pictures for display at more than one aspect ratio. Hollywood has been doing it for years - producing 4x3 tv versions from CinemaScope masters; protecting 4x3 viewers from 16x9 originals has to be a darn sight easier!
SI. Service Information, the basic overhead in a multiplex transmission which tells the IRD what services it has and what programmes are available
Simulcrypt The DVB has given its backing to two approaches to CA, simulcrypt and multicrypt. Simulcrypt is intended to permit different CA operators in different geographic areas. The service carries entitlement messages for each CA provider within an agreed common framework, but the viewer does not have a choice of SMS. In technical simulcrypt, the system is designed to allow two competing CA systems within an agreed framework. Multicrypt is an open system which makes use of the common interface to allow competing CA systems, subject only that the service provider must transmit entitlement messages for each CA provider.
SMC Subscriber Management Centre
StatMux. Statistical Multiplexing. for varying the datarate shot by shot according to the needs of the picture. (See also Dynamic Multiplexing)
STB Set-top Box. More properly referred to as an STU - Set-top Unit!
Time and Date Table - mandatory data transmitted within SI to synchronise the receiver's internal clock.
Viewer Preference - during installation routines, the television set or set-top box allows the viewer to set the preferred mode for viewing non-compatible aspect ratios on the display.
Virtual Machine - A virtual machine is a software concept whereby applets and programmes can be written which are independent of the microprocessor they are run on, so called "platform independence". The virtual machine takes the unified "bytecode" and interprets it for the particular hardware it is running on. This is particularly important for digital terrestrial television, where there will be a plurality of hardware from different manufacturers as techniques rapidly evolve.
WebTV - the name of a Microsoft company specialising in putting Internet content onto viewer's television sets via a set-top box. It is becoming a general term. Traditional broadcasters had better watch out - if they don't embrace it, Microsoft and others will surely "steal" the television set!
gloss.html - © 1996-04 Wolfgang Hahn - last updated: 01.03.04