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19’’ (19-inch) construction method
Rack mountable standardized chassis/cabinet for multiple equipment modules widely used to house professional entertainment, telecommunications and computing equipment.
The instruments are prepared with a front panel that is 19 inches wide (482,6mm) including perforated extensions to be fastened to a rack/frame with screws (some hardware producers simply use mounting brackets instead of an entire front panel).
2wcom makes the effort to define the installation height to 1U (rack unit) as possible. 1U is also standardized as multiples of 1,75 inches (44,45mm). The depth of the chassis varies as required.
AAC (HE v1&v2) Advanced Audio Coding
Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format (25 percent efficiency improvement), AAC generally achieves better sound quality than MP3 at similar bit rates. However this performance has more recently been considerably enhanced with aacPlus, also known as High Efficiency AAC (HE-AAC v2), and included in MPEG-4 and delivers CD quality stereo at 48 kb/s and 5.1 surround sound at 128 kb/s. HE-AAC v2, as version of AAC, is used for both DAB+ and DMB.
The digital audio standard officially known as AES3 and frequently called AES/EBU and also published as part of IEC 60958, is used for carrying digital audio signals between devices.
AF Alternative Frequencies (RDS Data)
Data subset of RDS data. This allows a receiver to re-tune to a different frequency providing the same station when the first signal becomes too weak (e.g. when moving out of range). This is often utilized in car stereo systems.
CSR's world renowned aptX™ audio compression solutions retain the full integrity of original digital audio and are optimised for instant real-time audio streaming. The suite of algorithms has earned a reputation for some of the highest audio quality, extremely low latency and strong resilience to bit errors, and has been proven in wireless, broadcast and professional live performance applications.
ASI Asynchronous Serial Interface
ASI is an interface for streaming data, which usually carries an MPEG Transport Stream (MPEG-TS).
An ASI signal can carry one or multiple SD, HD or audio programs that are already compressed, not like an uncompressed SD-SDI (270 Mbit/s) or HD-SDI (1.45 Gbit/s). An ASI signal can be at varying transmission speeds and is completely dependent on the user's setup requirements. As ASI employs 8B/10B channel encoding, the transmission rate of user data is limited to around 213 Mbit/s (coding and synchronisation).
This allows you to adjust an delay, an audio effect which records an input signal to an audio storage medium, and then plays it back after a period of time.
Audio over IP
Streaming audio over IP (AoIP) networks is being increasingly used by broadcasting companies, among others, to provide high-quality audio feeds over distance across an IP network such as the Internet. The application is also known as audio contribution over IP in reference to the programming contributions made by field reporters and remote events. Audio quality and delay (on duplex transmissions) are key issues for contribution links.
In the past these links have made widespread use of ISDN services but these are becoming increasingly difficult or expensive to obtain in some parts of Europe and are being phased out in others. At the same time prices for bandwidth have been fallen consequently over the last years. Many proprietary systems came into existence for transporting high quality audio over IP based on TCP, UDP or RTP. An interoperable standard for audio over IP using RTP now exists.
Frequency band between 174 and 230 MHz of the VHF range, used for DAB services (formerly used for analogue television).
BER Bit Error Rate
The bit error rate or bit error ratio (BER) is the number of bit errors
divided by the total number of transferred bits during a studied time
interval. BER is a unitless performance measure, often expressed
as a percentage number.
CA Conditional Access
Mechanism by which the users access to service components can be restricted.
A GSM Cell ID (CID) is a generally unique number used to identify each Base transceiver station (BTS) or sector of a BTS within a Location area code (LAC) if not within a GSM network.
CENELEC European Committee for Electrotechnical Standardization
CENELEC is responsible for European Standardization in the area of electrical engineering. Together with ETSI (telecommunication) and CEN (other technical areas) CENELEC form the European system for technical standardization.
Standards harmonised by these agencies are regularly adopted in many countries outside Europe which follow European technical standards.
A codec is a device or computer program capable of encoding and decoding a digital data stream or signal. The word codec is an abbreviation for 'coder-decoder'. A codec (the program) should not be confused with a coding or compression format or standard – a format is a document (the standard), a way of storing data, while a codec is a program (an implementation) which can read or write such files. In practice "codec" is sometimes used loosely to refer to formats, however.
A codec encodes a data stream or signal for transmission, storage or encryption, or decodes it for playback or editing. An analog-to-digital converter (ADC) converts its analog signals into digital signals, which are then passed through an encoder for digital transmission or storage. A receiving device then runs the signal through an decoder, then a digital-to-analog converter (DAC) restores the orginal signal.
COFDM Coded Orthogonal Frequency Division Multiplex
Modulation method (division into small units, chronological nesting, transmission on various carrier frequencies). COFDM is used in DAB, DAB+ and DMB.
CRC Cyclic Redundancy Check
A type of function that takes as input a data stream of any length and produces as output a value of a certain fixed size. Can be used as a checksum to detect accidental alteration of data during transmission or storage.
CT Clock Time (RDS Data)
CT is a subset of RDS data. Can synchronize a clock in the receiver or the main clock in a car. Due to transmission vagaries, CT can only be accurate to within 100 ms of UTC.
DAB Digital Audio Broadcasting, DAB+, DMB Digital Multimedia Broadcasting and Eureka 147
DAB (Digital Audio Broadcasting) is a method for transmission of digital radio signals especially suited, but not limited to mobile reception.
DAB has been under development since 1981 at the "Institut für Rundfunktechnik" (IRT). In 1985 the first DAB demonstrations were held at the WARC-ORB (World Administrative Radio Conference) in Geneva and in 1988 the first DAB transmissions were made in Germany. Later DAB was developed as a research project for the European Union (EUREKA), which started in 1987 on initiative by a consortium formed in 1986. The MPEG-1 Audio Layer II ("MP2") codec was created as part of the EU147 project. DAB was the first standard based on orthogonal frequency division multiplexing (OFDM) modulation technique, which since then has become one of the most popular transmission schemes for modern wideband digital communication systems.
DAB+ and DMB
The term DAB most commonly refers both to a specific DAB-standard using the MP2 audio codec, but can sometimes refer to a whole family of DAB related standards, such as DAB+, DMB and DAB-IP. DAB+ is an additional audio codec for 'Digital Audio Broadcasting', based on the new audio coding technology HE-AAC v2.
A decoder is a device which does the reverse of an encoder, undoing the encoding so that the original information can be retrieved. The same method used to encode is usually just reversed in order to decode.
Demodulation is the act of extracting the original information-bearing signal from a modulated carrier wave. A demodulator is an electronic circuit (or computer program in a software defined radio) that is used to recover the information content from the modulated carrier wave.
These terms are traditionally used in connection with radio receivers, but many other systems use many kinds of demodulators. Another common one is in a modem, which is a contraction of the terms modulator (transmitter)/demodulator (receiver).
DMB Digital Multimedia Broadcasting
Digital Multimedia Broadcasting (DMB) is a - now obsolete - digital transmission system for television, radio and datacasting to mobile devices/phone and can operate ovr stallite (S-DMB) or terrestrially (T-DMB). DMB is based on the Eureka 147 Digital Audio Broadcasting (DAB) standard, and has similarities with DVB-H, a competing mobile TV standard. T-DMB (ETSI standard TS 102 427 and TS 102 428) uses MPEG-4 H.264 for video and HE-AAC V2 for the audio, together encapsulated in an MPEG-2 transport stream (TS). The encoded TS is broadcast on DAB in data stream mode. Application devices include mobile phones, portable TV, and PDAs as well as data/radio for cars.
A downlink (DL) is the link from a satellite to a ground station. An uplink is the inverse of a downlink.
DQPSK Differential Quadrature Phase-Shift Keying
Digital phase modulation scheme that conveys data by changing or modulating the phase of the carrier wave. DQPSK is used in DAB, DAB+ and DMB.
DRM Digital Radio Mondiale
Method for the transmission of digital VHF radio signals (AM), deleloped by the DRM consortium.
DSNG Digital Satellite News Gathering
Digital Satellite News Gathering (DSNG) is the digital form of analog Satellite News Gathering (SNG).
Electronic news-gathering (ENG) became a catch-all term for various elements of the electronic news gathering process, including the use of point-to-point terrestrial microwave signals to backhaul the remote signal to the studio. In modern news operations, however, it also includes SNG (satellite news gathering) and DSNG (digital satellite news gathering). ENG field operations are usually done with a specially modified truck or van. Terrestrial microwave vehicles can usually be identified by their masts which can be extended up to 50 feet (15 m) in the air (to allow line-of-sight with the station's receiver antennas), while satellite trucks normally use a dish that points skywards towards one of the geostationary communications satellites. New phased array satellite antennas are, as of 2010, being adapted from military and aircraft applications for news gathering by networks and local stations. These systems will allow for live broadcasts out of moving vehicles.
DTV Digital Television
DTV is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV. Countries all over the world are replacing over-the-air broadcast analog television with digital television to allow other uses of the radio spectrum formerly used for analog TV broadcast.
DVB Digital Video Broadcasting
The DVB consortium, with over 200 memebers in 25 countries, which developed the preferred scheme for digital broadcasting in Europe. They set of standards that define digital broadcasting using existing satellite (DVB-S/S2), cable (DVB-C/C2), and terrestrial (DVB-T) infrastructures. (You can find lists and maps of countries and territories using DVB-T on Wikipedia.org)
Digital Video Broadcasting Asynchronous Serial Interface. With this interface, a fully produced MPEG-2 transport stream can be transmitted via a BNC cable or fibre optics at a data rate of 270MBit/s. The transport stream includes video and audio data as well as additional information. ASI is specified in EN50083-9.
DVB-C Digital Video Broadcasting via Cable
DVB-C stands for Digital Video Broadcasting - Cable and it is the DVB European consortium's standard for the broadcast transmission of digital television over cable. This system transmits an MPEG-2 or MPEG-4 family digital audio/video stream, using a QAM modulation with channel coding.
DVB-S Digital Video Broadcasting via Satellite
DVB-S is an abbreviation for Digital Video Broadcasting — Satellite; is the original Digital Video Broadcasting forward error coding and emodulation standard for satellite television and dates from 1994, in its first release, while development lasted from 1993 to 1997. The first application was commercially available in France via Canal+, enabling digitally broadcast, satellite-delivered television to the public.
It is used via satellites serving every continent of the world. DVB-S is used in both multiple channel per carrier (MCPC) and SCPC modes for broadcast network feeds, as well as for direct broadcast satellite services like Sky Digital (UK) via Astra in Europe, Dish Network and Globecast in the U.S. and Bell TV in Canada.
While the actual DVB-S standard only specifies physical link characteristics and framing, the overlaid transport stream delivered by DVB-S is mandated as MPEG-2, known as MPEG transport stream (MPEG-TS).
DVB-S2 Digital Video Broadcasting via Satellite - Second Generation
Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) is designed as a successor for the popular DVB-S digital television broadcast standard, and was developed in 2003 and ratified by ETSI (EN 302307) in March 2005. It is based on DVB-S and the electronic news-gathering (or Digital Satellite News Gathering) standard, used by mobile units for sending sounds and images from remote locations world-wide back to their home television stations.
DVB-S2 is envisaged for broadcast services including standard and HDTV, interactive services including Internet access, and (professional) data content distribution. The development of DVB-S2 coincided with the introduction of HDTV and H.264 (MPEG-4 AVC) video codecs.
Two new key features that were added compared to the DVB-S standard are:
- A powerful coding scheme based on a modern LDPC code.
- VCM (Variable Coding and Modulation) and ACM (Adaptive Coding and Modulation) modes, which allow optimizing bandwidth utilization by dynamically changing transmission parameters.
Other features include enhanced modulation schemes up to 32APSK, additional code rates, and the introduction of a generic transport mechanism for IP packet data including MPEG-4 audio–video streams, while supporting backward compatibility with existing MPEG-2 TS based transmission.
The standard document claims that the DVB-S2 performance gain over DVB-S is around 30% at the same satellite transponder bandwidth and emitted signal power. When the contribution of improvements in video compression is added, an (MPEG-4 AVC) HDTV service can now be delivered in the same capacity that supported an early DVB-S based MPEG-2 SDTV service only a decade before.
DVB-T and DVB-T2 Digital Video Broadcasting Terrestrial
DVB over IP
Refers to delivery of digital television services (DVB) to homes over broadband IP networks. This could be supplied via cable or, possibly over copper telephone lines using high-speed DSL and the supplier could then achieve 'triple play' - bundling voice (over-IP) telephone as well as Internet with the television service. This has great potential for interactive television as it includes a built-in fast return link to the service provider.
or E1 carrier. E-carrier is a European telecommunications standard. The level 1 is a wire technology used by telecommunication operators with 2 Mbit/s data rate.
EDI Encapsulation for DAB Distribution Interfaces
EDI is an adaption of the Ensemble Transport Interface (ETI) for IP networks. EDI is standardized at ETSI: TS 102 693. EDI is the structured transmission of data between organizations by electronic means. In case of data transmission via satellite EDI means E1 data transmission via IP. The main advantage is that compared to ETI there is no need of a dedicated line.
DAB Ensemble data stream via EDI means ETI via IP.
In computer networking, encapsulation is a method of designing modular communication protocols in which logically separate functions in the network are abstracted from their underlying structures by inclusion or information hiding within higher level objects.
The physical layer is responsible for physical transmission of the data. Link encapsulation allows local area networking and IP provides global addressing of individual computers; UDP adds application or process selection, i.e., the port specifies the service such as a Web or TFTP server.
Encapsulation is a characteristic feature of most networking models, including the OSI Model and TCP/IP Suite of protocols.
Encoder / Encoding
An encoder is a device that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.
An audio encoder may be capable of capturing, compressing and converting audio.
A video encoder may be capable of capturing, compressing and converting audio/video.
A multiplexer combines multiple inputs into one output.
In cryptography, is the process of transforming information (referred to as plaintext) using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. In conditional access broadcasts this is used to make transmissions secure and is often found on satellite or cable systems. The result of the process is information. In many contexts, the word also implicitly refers to the reverse process, to make the encrypted information readable again. Encryption and content security are vital to the growth of digital media markets.
Entity of programme and data services (usually about 9 to 12 programmes DAB or about 18 to 32 programmes DAB+) with a fixed total capacity which is processed and transmitted.
The DAB multiplex data stream has a maximum capacity of 2.25 Mbit/s, normally shared by a number of services (radio / data). The term "multiplex" relates to the fact that the individual data streams are multiplexed (that is, they are transmitted alternately in chunks). A multiplex needs a bandwidth of about 1.5 MHz on the frequency band.
EON Enhanced Other Networks (RDS Data)
EON is a subset of RDS data. It allows the receiver to monitor other networks or stations for traffic programmes, and automatically temporarily tune into that station.
EPG Electronic Program Guide
DTV allows broadcasters to transmit electronic program guides. For many, this service is considered essential to keep viewers up to date with, and enable them to navigate between the increased number of channels DTV brings. The program guide database allows a receiver to build an on-screen grid of program information, contains control information to ease navigation and makes it possible for the viewer/listener to navigate, select, discover and record content by time, title, channel, genre, etc.
ES Elementary Stream
Consecutive flow of (compressed) mono-media data, i.e. one of the coded audio, coded video or other coded bitstreams.
Ethernet is a family of frame-based computer networking technologies for local area networks (LAN). It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model as well as a common addressing format and Media Access Control at the Data Link Layer.
ETI Ensemble Transport Interface
Ensemble Transport Interface, a communications standard used in Digital Audio Broadcasting (DAB). The ETI is a standardised output stream from a DAB/DAB+/T-DMB multiplexer. It consists of a 2Mbit/s synchronous stream. Network adaption is defined for G.703 lines (E1) that is the typical physical interface used between the multiplexer and DAB OFDM modulator. The ETI stream can also be recorded to a file for capture and replay. ETI is standardized at ETSI: EN 30 799
ETSI European Telecommunications Standards Institute
The European Telecommunications Standards Institute. Its mission is to produce lasting telecommunications standards for Europe and beyond. ETSI has 655 members from 59 countries inside and outside europe, and represents administrations, network operators, manufacturers, service providers, research bodies and users.
A compression techniqe, based on DCT. Unlike MPEG, which is asymmetrical having complex coders and simpler decoders and is designed for broadcast, this is symmetrical with the same processing power at the coder and decoder.
FEC Forward Error Correction
Forward Error Correction, in the form of Reed-Solomon (RS) outer error protection and outer interleaving, can be applied to sub-channels carrying service components in packet mode in order to further increase the error robustness of DAB data delivery. RS is also used in DVB-S/S2.
FIB Fast Information Block
The FIB contains 256 bits and comprises an FIB data field and a CRC. The FIB data field consists of one or more Fast Information Group (FIG).
FIC Fast Information Channel
The FIC is a non-time-interleaved data channel with fixed equal error protection. In particular it is used to send the DAB Multiplex Configuration Information (MCI) and optionally Service Information and data services.
FIG Fast Information Group
The FIG carries the following parts: Multiplex Configuration Information (MCI), Service Information (SI), FIC Data Channel (FIDC) and Conditional Access (CA).
FM Frequency Modulation
In telecommunications and signal processing, frequency modulation (FM) conveys information over a carrier wave by varying its instantaneous frequency. This is in contrast with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant. In analog applications, the difference between the instantaneous and the base frequency of the carrier is directly proportional to the instantaneous value of the input signal amplitude. Digital data can be sent by shifting the carrier's frequency among a set of discrete values, a technique known as frequency-shift keying.
FM is widely used for broadcasting of music and speech, and in two-way radio systems, in magnetic tape recording systems, and certain video transmission systems. In radio systems, frequency modulation with sufficient bandwidth provides an advantage in cancelling naturally-occurring noise. Frequency-shift keying (digital FM) is widely used in data and fax modems.
FTP File Transfer Protocol
The high level Internet standard protocol for transferring files from one machine to another. FTP is usually implemented at the application level.
Gigabit Ethernet (GbE or 1 GigE) is a term describing various technologies for transmitting Ethernet frames at a rate of one gigabit per second, as defined by the IEEE 802.3-2008 standard.
Ethernet is a family of frame-based computer networking technologies for local area networks (LAN). It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model as well as a common addressing format and Media Access Control at the Data Link Layer.
Ethernet is standardized as IEEE 802.3. The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology.
GPI General Purpose Interface
This is a simple form of control interface typically used for cueing equipment - usually by a contact closure (relais). It is simple, can be frame accurate and therefore can easily be applied over a wide range of equipment.
General Purpose Input/Output (a.k.a. GPIO) is a generic pin on a chip whose behavior (including whether it is an input or output pin) can be controlled (programmed) through software.
GPIO pins have no special purposes on themselves, and go unused by default. The idea is that sometimes the system integrator building a full system that uses the chip might find useful to have a handful of additional digital control lines, and having these available from the chip can save the hassle of having to arrange additional circuitry to provide them. For example, audio codecs have 4 GPIO pins, which go unused by default.
The Global Positioning System (GPS) is a space-based global navigation satellite system (GNSS) that provides reliable location and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS satellites. It is maintained by the United States government and is freely accessible by anyone with a GPS receiver.
IP Internet Protocol
The Internet Protocol (IP) is the principal communications protocol used for relaying datagrams (packets) across an internetwork using the Internet Protocol Suite. Responsible for routing packets across network boundaries, it is the primary protocol that establishes the Internet.
IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering datagrams from the source host to the destination host solely based on their addresses. For this purpose, IP defines addressing methods and structures for datagram encapsulation.
IP over DVB
The delivery of IP data and services over DVB broadcast networks. Also referred to as datacasting, this takes advantage of the very wideband data delivery systems designed for the broadcast of digital television, to deliver IP-based data services - such as file transfers, multimedia, Internet and carousels, which may complement, or be instead of, TV. One way to transmit IP data in a MPEG2-TS is by implementing multiprotocol encapsulation (MPE).
Internet Protocol Television is the use of the IP packetized data transport mechanism for delivery of streamed realtime television signals across a network. Data distribution usually uses IP multicast in IP TV.
IRD Integrated Receiver Decoder
A device that has both a demodulator and a decoder (e.g. for MPEG 2) built in. This could be a digital television set or a digital set-top box.
Frequency band between 1 and 2,6 GHz of the UHF range, used for local DAB/DMB services.
MCPC Multiple Channel per Carrier
On communications satellites which carry broadcast television networks and radio networks, this is known as multiple channel per carrier or MCPC. Where multiplexing is not practical (such as where there are different sources using a single transponder), single channel per carrier mode is used.
With multiple channels per carrier (MCPC), several subcarriers are combined into a single bitstream before being modulated onto a carrier transmitted from a single location to one or more remote sites. This uses time-division multiplexing (TDM). It is a retronym of sorts, as it was the only way radio networks were transmitted ("piggybacked" on television networks) until SCPC.
In digital radio and digital television, an ensemble or other multiplex or multichannel stations can be considered MCPC, though the term is generally only applied to satellites.
The major disadvantage of MCPC is that all of the signals must be sent to a single place first, then combined for retransmission — a major reason for using SCPC instead.
The modulation error ratio or MER is a measure used to quantify the performance of a digital radio transmitter or receiver in a communications system using digital modulation (such as QAM). A signal sent by an ideal transmitter or received by a receiver would have all constellation points precisely at the ideal locations, however various imperfections in the implementation (such as noise, low image rejection ratio, phase noise, carrier suppression, distortion, etc.) or signal path cause the actual constellation points to deviate from the ideal locations.
Transmitter MER can be measured by specialised equipment, which demodulates the received signal in a similar way to how a real radio demodulator does it. Demodulated and detected signal can be used as a reasonably reliable estimate for the ideal transmitted signal in MER calculation.
MIP Mega-frame Initialization Packet
In a Single Frequency Network, the transmitters and receivers are usually synchronized with the others, using GPS or a signal from the main station or network as a reference clock. For example, the DVB forum specifies the use of a special marker, the Mega-frame Initialization Packet (MIP) that is inserted in the bit stream at a central distribution point, and signals the SFN transmitters the absolute time (as read from a GPS receiver) at which this point in the data stream is to be broadcast.
MPEG-1 or MPEG-2 Audio Layer 3 (or III), more commonly referred to as MP3, is a patented high-performance digital audio encoding format using a form of lossy data compression. It is a common audio format for consumer audio storage, as well as a de facto standard of digital audio compression for the transfer and playback of music on digital audio players. (MP3 is claimed to achieve 'CD quality')
The 'Moving Picture Experts Group' (MPEG) is a working group of experts that was formed by ISO and IEC to set standards for audio and video compression and transmission.
MPEG-1 and MPEG-2
MPEG-1 is the standard on which such products as Video CD and MP3 are based. MPEG Audio Layer II (Synonyms: MP2, MPEG-1 Layer II, MUSICAM) is an audio codec defined by ISO/IEC 11172-3. It is a dominant encoding standard for audio broadcasting as part of the DAB digital radio and DVB digital television standards, and it is the core of the better known MP3 standard.
MPEG-2 is the standard on which such products as Digital Television set top boxes and DVD are based.
MPEG encoding is the process of capturing (digitizing) or converting (re-encoding) video and/or audio to one of several MPEG video and/or audio standards for distribution (Internet, LAN, Satellite, Cable, Terrestrial...).
Not only used as a synonym for HE-AAC v2. The standard for multimedia for the fixed and mobile web. MPEG-4 absorbs many o f the features of MPEG-1 and 2 and other related standards, adding new features. It is a collection of methods defining compression of audio and visual (AV) digital data. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications.
MPE Multiprotocol Encapsulation
MPE is a Data link layer protocol defined by DVB which has been published as part of ETSI EN 301 192. It provides means to carry packet oriented protocols (like for instance IP) within of MPEG transport stream (TS).
MSC Main Service Channel
The MSC is a time-interleaved data channel divided into a number of sub-channels which are individually convolutionally coded, with equal or unequal error protection. Each sub-channel may carry one or more service components. Used to carry audio and data service components.
Generally describes a collection of communications channels bundled into one transport system. For example, voice and data co-exist on a phone line carrying conversation and Internet access. In digital television 'a multiplex' describes a group of compressed digital video and audio channels multiplexed into single transmission stream occupying the space of one analog TV channel.
The multiplex in FM transmission (usually called MPX) is comprised of audio (mono and/or stereo), pilot tone, RDS (or RDBS) data and sometimes additional digital data.
Multiplex also names the output of a multiplexer (often used as a synonym for ensemble).
MUSICAM Masking Pattern Adapted Universal Subband Integrated Coding And Multiplexing
Used as a synonym for MPEG Audio Layer II
OFDM Orthogonal Frequency-Division Multiplexing
Used as a synonym for COFDM
PER Packed Encoding Rules
Packed encoding rules (PER) are ASN.1 encoding rules for producing a compact transfer syntax for data structures described in ASN.1, defined in 1994.
PER provides a much more compact encoding than BER. It uses additional information, such as the lower and upper limits for numeric values, from the ASN.1 specification to represent the data units using the minimum number of bits. The compactness requires that the decoder knows the complete abstract syntax of the data structure to be decoded, however.
PES Packetized Elementary Stream
Packetized audio, video or data elementary stream (ES) to be fed into the transport stream (TS) multiplexer.
PI Programme Identification (RDS Data)
PI is a subset of RDS data. This is the unique code that identifies the station. Every station receives a specific code with a country prefix. In the US, PI is determined by applying a formula to the station's call sign.
PID Packet Identifier
Each table or elementary stream in a transport stream is identified by a 13-bit packet ID (PID). A demultiplexer extracts elementary streams from the transport stream in part by looking for packets identified by the same PID. In most applications, Time-division multiplexing will be used to decide how often a particular PID appears in the transport stream.
PS Programme Service (RDS Data)
This is simply an eight-character static display that represents the call letters or station identity name. Most RDS capable receivers display this information and, if the station is stored in the receiver's presets, will cache this information with the frequency and other details associated with that preset.
It is also possible to use names longer than eight characters with the so called "Scrolling PS". In this case the word is shifted through the display by dynamically changing the PS.
PSI Program Specific Information
Program Specific Information (PSI) is metadata about a program (channel) and part of a MPEG transport stream.
The PSI data contains five tables:
- PAT (Program Association Table)
- CAT (Conditional Access Table)
- PMT (Program Map Table)
- NIT (Network Information Table)
- TDT (Time and Date Table)
PSI is carried in the form of a table structure. The table structure can span multiple transport stream packets. Adaptation field also occurs in TS packets carrying PSI data. The PSI data will never be scrambled so that the decoder at the receiving end can easily identify the properties of the stream.
The PAT, CAT and TDT tables are associated with predefined PID as explained in the respective sections. There may be multiple independent PMT tables in a stream; these are given user-defined PID numbers (as are PES packets). PMT table PIDs are defined in the PAT, and are the only PIDs defined there (PES PIDs are defined in the PMT). Each table has predefined structure.
PTY Programme Type (RDS Data)
PTY is a subset of RDS data. This coding of up to 31 pre-defined programme types – e.g. (in Europe): PTY1 News, PTY6 Drama, PTY11 Rock music, – allows users to find similar programming by genre. PTY31 seems to be reserved for emergency announcements in the event of natural disasters or other major calamities.
RBDS Radio Broadcast Data System
Radio Broadcast Data System (RBDS) is the official name used for the U.S. version of RDS. The two standards are only slightly different.
RDS Radio Data System
Radio Data System, or RDS, is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. The RDS system standardises several types of information transmitted, including time, station identification and programme information.
A broadcast relay station, relay transmitter, broadcast translator (U.S.), rebroadcaster (Canada), or repeater (two-way radio) is a broadcast transmitter which relays, repeats, or reflects the signal of another radio station or television station, usually to an area not covered by the signal of the originating station. They may serve, for example, to expand the broadcast range of a television or radio station beyond the primary signal's coverage area, or to improve service in a part of the main coverage area which receives a poor signal due to geographic constraints. They may be (but are not usually) used to create a single-frequency network.
REG Regional (RDS Data)
REG is a subset of RDS data. This is mainly used in countries where national broadcasters run "region-specific" programming such as regional opt-outs on some of their transmitters. This functionality allows the user to "lock-down" the set to their current region or let the radio tune into other region-specific programming as they move into the other region.
Error-correcting code that works by oversampling a polynomial constructed from the data. The polynomial is evaluated at several points, and these values are sent or recorded. By sampling the polynomial more often than is necessary, the polynomial is over-determined. As long as "many" of the points are received correctly, the receiver can recover the original polynomial even in the presence of a "few" bad points. Reed-Solomon error correction is used in DAB+, DMB and DVB-S/S2.
RT or RT+ (Radio Text or Radio Text Plus) (RDS Data)
RTP Real-time Transport Protocol
The Real-time Transport Protocol (RTP) defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications and web-based push-to-talk features.
RTP is used in conjunction with the RTP Control Protocol (RTCP). While RTP carries the media streams (e.g., audio and video), RTCP is used to monitor transmission statistics and quality of service (QoS) and aids synchronization of multiple streams. When both protocols are used in conjunction, RTP is originated and received on even port numbers and the associated RTCP communication uses the next higher odd port number.
SCPC Single Channel per Carrier
Single channel per carrier (SCPC) refers to using a single signal at a given frequency and bandwidth. Most often, this is used on broadcast satellites to indicate that radio stations are not multiplexed as subcarriers onto a single video carrier, but instead independently share a transponder. It may also be used on other communications satellites, or occasionally on non-satellite transmissions.
In an SCPC system, satellite bandwidth is dedicated to a single source. This makes sense if it is being used for something like satellite radio, which broadcasts continuously. Another very common application is voice, where a small amount of fixed bandwidth is required. However, it does not make sense for burst transmissions like satellite internet access or telemetry, since a customer would have to pay for the satellite bandwidth even when they were not using it.
Where multiple access is concerned, SCPC is essentially FDMA. Some applications use SCPC instead of TDMA, because they require guaranteed, unrestricted bandwidth. As satellite TDMA technology improves however, the applications for SCPC are becoming more limited.
- simple and reliable technology
- low-cost equipment
- any bandwidth (up to a full transponder)
- usually 64 kbit/s to 50 Mbit/s
- easy to add additional receive sites (earth stations)
- inefficient use of satellite bandwidth for burst transmissions, typically encountered with packet data transmission
- usually requires on-site control
- When used in remote locations, the transmitting dish must be protected.
- A dish which is moved out of alignment can result in fines as high as $1,100 per minute (as of 2003) from the satellite operator.
SDT Service Description Table
The Service Description Table (SDT) is one of the DVB Service Information tables. The SDT describes services which are part on an MPEG transport stream.
There is one SDT per transport stream. The SDT may include name of the service, service identifier, service status, and whether or not the service is scrambled.
SFN Single Frequency Network
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel - all are sharing the same radio frequency to achieve a large area coverage.
Analogue FM and AM radio broadcast networks as well as digital broadcast networks can operate in this manner. SFNs are not generally compatible with analogue television transmission, since the SFN results in ghosting due to echoes of the same signal.
A simplified form of SFN can be achieved by a low power co-channel repeater, booster or broadcast translator, which is utilized as gap filler transmitter.
The aim of SFNs is efficient utilization of the radio spectrum, allowing a higher number of radio and TV programs in comparison to traditional multi-frequency network (MFN) transmission. An SFN may also increase the coverage area and decrease the outage probability in comparison to an MFN, since the total received signal strength may increase to positions midway between the transmitters.
SI Service Information (MPEG2-TS)
The SI provides supplementary information about audio and data services, which is not included in the Multiplex Configuration Information (MCI). The Service Information (SI) features which may be carried in the FIC include the following: service component language, service linking, date and time, Programme Number, Programme Type (PTy), announcements, regional identification, other ensembles, FM and AM services information, frequency information, transmitter identification information, ensemble, service and service component labels, etc.
DVB defined tables:
- NIT (Network Information Table)
- SDT (Service Descriptor Table)
- BAT (Bouquet Association Table)
- EIT (Event Information Table)
- RST (Running Status Table)
- TDT (Time & Date Table)
- TOT (Time Offset Table)
- ST (Stuffing Table)
SNG Satellite News Gathering
SNMP Simple Network Management Protocol
SNMP is the Internet standard protocol developed to manage nodes (servers, workstations, routers, switches, hubs, etc.) on IP networks. It enables network administrators to manage network performance, find and solve network problems, and plan for network growth. SNMP works by sending Protocol Data Units (PDUs) messages to different parts of a network. Agents, SNMP-compliant devices, store data about themselves in Management Information Bases (MIPs) and return this data to the SNMP requesters.
SNR Signal-to-Noise Ratio (S/N or SNR)
Signal-to-noise ratio (often abbreviated SNR or S/N) is a measure used in science and engineering to quantify how much a signal has been corrupted by noise. It is defined as the ratio of signal power to the noise power corrupting the signal. A ratio higher than 1:1 indicates more signal than noise.
SNR = P (Signal) / P (Noise) P = average Power
Noise can make pictures look grainy or adding hiss to sound. Digitally generated images or sounds are theoretically capable of being pure - noise-free - having an infinite signal to noise ratio.
Stream Mode (DAB/DAB+)
Mode of data transmission allowing one service component per sub-channel to be transmitted transparently at a fixed bit rate.
Streaming (video and/or audio)
Refers to suppliying a constant service, often realtime, of a medium. Although broadcast TV has done this from the beginning, the term is one more usually associated with delivery by networks, including the Internet. The transmission comprises a stream of data packets which can be viewed/heard as they arrive though are often buffered, stored slightly in advance of viewing, to compensate for any short interruptions of delivery.
Connecting network users via a switch means that each can be sending or receiving data at the same time with the full wire-speed of the network available. This is made possible by the aggregate capacity of the switch. So, for example, an eight-port Gigabit Ethernet switch will have an aggregate capacity of 8 Gb/s. This means many simultaneous high-speed transactions taking place without interruption from other users.
TA, TP Traffic Announcement, Traffic Programme (RDS Data)
Those data are a subset of RDS data. The receiver can often be set to pay special attention to this flag and e.g. stop the tape/pause the CD or retune to receive a Traffic bulletin. The TP flag is used to allow the user to find only those stations that regularly broadcast traffic bulletins whereas the TA flag is used to stop the tape or raise the volume during a traffic bulletin.
TCP/IP Transfer Control Protocol/Internet Protocol
A set of standards that enables the transfer of data between computers. Besides its application directly to the Internet it is also widely used throughout the computer industry. It was designed for transferring data files rather than large files of television or film pictures. Thus, althought TCP/IP has the advantage of being widely compatible it is a relatively inefficient way of moving picture files. For streaming applications the user data protocol (UDP) or a combination of UDP and real-time protocol (RTP) are used instead.
T-DMB Terrestrial Digital Multimedia Broadcasting
Used as a synonym for DMB (terrestrial).
TMC Traffic Message Channel (RDS Data)
TMC is a subset of RDS data. Digitally encoded traffic information. Not all RDS equipment supports this. Often available for Automotive navigation systems. In many countries only encrypted data is broadcast, and so a subscription and appropriate decoder is required to use.
TS Transport Stream
Communications protocol for audio, video, and data. Allows multiplexing of digital video and audio and synchronisation of the output, and offers features for error correction for transportation over unreliable media.
UECP Universal Encoder Communication Protocol
UECP-protocol (Universal Encoder Communication Protocol) serves for the digital communication and control between a broadcasting studio of a radio transmitter and the claimant VHF/FM transmitters.
UHF Ultra high frequency
Range of electromagnetic waves whose frequency is between 300 MHz and 3 GHz (3,000 MHz). Also known as the decimeter band or decimeter wave as the wavelengths range from ten to one decimeters.
An uplink (UL or U/L) is the portion of a communications link used for example for the transmission of signals from an Earth terminal to a satellite or to an airborne platform. An uplink is the inverse of a downlink.
UDP User Datagram Protocol
The User Datagram Protocol (UDP) is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths.
UDP uses a simple transmission model without implicit hand-shaking dialogues for providing reliability, ordering, or data integrity. Thus, UDP provides an unreliable service and datagrams may arrive out of order, appear duplicated, or go missing without notice. UDP assumes that error checking and correction is either not necessary or performed in the application, avoiding the overhead of such processing at the network interface level. Time-sensitive applications often use UDP because dropping packets is preferable to waiting for delayed packets, which may not be an option in a real-time system. If error correction facilities are needed at the network interface level, an application may use the Transmission Control Protocol (TCP) or Stream Control Transmission Protocol (SCTP) which are designed for this purpose.
VHF Very High Frequency
Radio frequency range from 30 MHz to 300 MHz, also known as the meter band or meter wave as the wavelengths range from ten to one meters. Popular members are FM radio or digital TV like DVB-T.
WorldDMB or WorldDAB or World DMB Forum
The WorldDMB Forum is an international non-governmental organisation whose objective is to promote, harmonise and co-ordinate the implementation of DAB Digital services based on the Eureka 147 DAB system. It is dedicated to encouraging international co-operation and co-ordination between sound and data broadcasters, network providers, manufacturers, governments and official bodies, thus gaining consensus for the smooth introduction of DAB based services.
X.21 (sometimes referred to as X21) is an interface specification for differential communications introduced in the mid 1970s by the ITU-T. X.21 was first introduced as a means to provide a digital signaling interface for telecommunications between carriers and customers' equipment. This includes specifications for DTE/DCE physical interface elements, alignment of call control characters and error checking, elements of the call control phase for circuit switching services, and test loops.
When X.21 is used with V.11, it provides synchronous data transmission at rates from 100 kbit/s to 10 Mbit/s. There is also a variant of X.21 that is only used in select legacy applications, “circuit switched X.21”. X.21 normally is found on a 15-pin D-Sub connector and is capable of running full-duplex data transmissions.
The Signal Element Timing, or clock, is provided by the carrier (your telephone company), and is responsible for correct clocking of the data. X.21 is primarily used in Europe and Japan, for example in the Scandinavian DATEX and German DATEX-L circuit switched networks during the 1980s.
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