Glossary
Instruction Manual: Professional Decoder
Page A-3
ST.TM.TT1220.1
dB (Decibels)
A ratio of one quantity (usually signal power) to another. Common variants are suffixed by an additional letter
signifying that a single power measurement is referenced to a standard value:
dBm - decibels relative to 1 mW
dBW - decibels relative to 1 W.
DCE
Data Communications Equipment.
DCT (Discrete Cosine
Transform)
An invertible, discrete orthogonal transformation. The values associated with blocks of pixel samples are transformed
from the spatial domain into the frequency domain, producing coefficients in which spatially redundant information
can be removed. Can be forward DCT or inverse DCT.
DDS
Direct Digital Synthesiser.
Decoder
The unit containing the electronic circuitry necessary to decode encrypted signals. Some decoders are separate from
the receiver but, in satellite TV broadcasting, the term is often used interchangeably as a name for an Integrated
Receiver Decoder (IRD). (The term IRD, or IRD/Decoder, is usually associated with satellite TV broadcasting while
Cable systems are based on Converters or on Set-Top Boxes/Converters.)
Decoding Time-stamp
A field that may be present in a PES packet header that indicates the time that an access unit is to be decoded in the
system target decoder.
Differential Coding
Method of source coding using the difference between the value of a sample and a predicted value.
DIL
Dual In Line.
DIN
Deutsches Institut für Normung.
Downlink
The part of the communications satellite circuit that extends from the satellite to the Earth.
DPCM (Differential Pulse
Code Modulation)
A process in which a signal is sampled and the difference between each sample of a signal and its predicted value is
derived from the succession of quantised values is converted by coding into a digital signal.
DSNG
Digital Satellite News-Gathering.
DSP
Digital Signal Processor.
DTE/DCE (Data Terminal
Equipment/Data
Communication Equipment)
Components in a packet switching network.
DTH (Direct To Home)
The term used to describe uninterrupted transmission from the satellite directly to the subscriber - that is, no
intermediary cable or terrestrial network utilised.
DVB (Digital Video
Broadcasting)
A European project which has defined transmission standards for digital broadcasting systems using satellite (DVB-
S), cable (DVB-C) and terrestrial (DVB-T) media, created by the EP-DVB group and approved by the ITU. Specifies
modulation, error correction, etc. (see EN 300 421). DVB-PI refers to DVB Professional Interfaces.
DVB SI
Digital Video Broadcasting Service Information.
Earth
Technical Earth: Ensures that all equipment chassis within a rack are at the same potential, usually by connecting a
wire between the Technical earth terminal and a suitable point on the rack. This is sometimes known as a Functional
earth.
Protective Earth: Used for electric shock protection. This is sometimes known as a safety earth.
EBU
European Broadcast Union.
ECM
Entitlement Control Message.
EIA
Electronics Industries Association (USA).
EIT (Event Information
Table)
A component of the Service Information (SI) stream which contains information about events or programmes such as
event name, start time, duration, etc.
Elementary Stream
A generic term for a coded video, coded audio or coded other bit-stream.
EMC
Electromagnetic Compatibility.
EMM
Entitlement Management Message.
Ethernet
A means by which machines are connected and communicate over a network.
ETS
European Telecommunications Standard.
ETSI
European Telecommunications Standards Institute.
FCC
Federal Communications Commission.
FDM (Frequency Division
Multiplex)
A common communication channel for a number of signals, each with its own allotted frequency.