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Glossary of Terms

 
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A

AAC
Advanced Audio Coding (
MPEG-2).

ACATS
FCC Advisory Committee on Advanced Television Service.

Access Unit
A coded representation of a presentation unit. For audio, an access unit is the coded representation of an audio frame; for video, an access unit is the coded representation of a picture.

ACK
Acknowledge signal (type II and type II handshake).

A/D or ADC
Analog-to-Digital Converter. A circuit that converts an analog signal, having a continuously varying amplitude, to a digitally quantized representation using binary output signals.

ADPCM
Adaptive Differential Pulse Code Modulation.

ADSI
Analog Display Services Interface (type III protocol). A subscriber feature than enables transfers and display of larger amounts of data.

ADSL
Asymmetrical Digital Subscriber Line. A twisted-pair-based distribution system providing transmission rates up to 6.3 Mb/s.

ADTV
Advanced Digital Television. An HDTV system proposed by the Advanced Television Research Consortium, consisting (in 1992) of David Sarnoff Research Center, North American Philips, Thomson Consumer Electronics, NBC, and Compression Labs, Inc.

AF
Alternative Frequencies. This list is compiled in memory within the receiver of nearby broadcast stations that carry the same program. This is to allow the motorist who is traveling away from his local station to automatically switch to the next geographically located station for continuation of the same program (such as NPR).

AFC
Automatic Frequency Control.

Aliasing
Image artifacts in captured images caused by significant energy in the scene at frequencies higher than the Nyquist limit of the sensor. In single-chip color cameras, aliasing can produce unexpected color patterns in highly detailed monochrome objects.

ASIC
Application-specific integrated circuit. An IC designed for a custom requirement, frequently implemented in a gate array or field programmable array.

ASK
Amplitude Shift Keying. A digital amplitude modulation method.

ATC
Adaptive Transform Coding.

ATM
1. Asynchronous Time Multiplex.
2. Asynchronous Transfer Mode.

ATRAC
Adaptive Transform Acoustic Coding (Sony).

ATV
Advanced Television. The term is often used interchangeably with HDTV.

Audio Bandwidth
The signal range from 20 Hz to 20 kHz, according to the standard specification, although there is some evidence of acoustic perception outside that bandwidth in exceptional individuals, particularly young children.

AWGN
Additive White Gaussian Noise.

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B

BBC
British Broadcasting Corporation.

BC
Backward Compatibility.

BCH
Bose-Chaudhuri-Hocquenghem.

BD
Block Difference.

BER
Bit Error Rate. A measure of the probability of bit error in a communication system.

Bit Rate
The rate at which the compressed bitstream is delivered from the channel to the input of a decoder.

BMA
Block Matching Algorithm.

bpp
Bits per pixel (picture element or pel).

Brightness
The aspect of perception that changes as the intensity of a patch of light is varied.

BS
Base Station.

Byte Aligned
A bit in a coded bitstream is byte-aligned if its position is a multiple of 8 bits from the first bit in the stream.

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C

C/N
Carrier/Noise ratio.

CA
Conditional Access. A mechanism by which the user access to service components can be restricted.

CAS
CPE alerting signal (type II and type III handshake).

CAT
Conditional Access Table, provides the association between one or more conditional access systems, their entitlement management message streams, and any special parameters associated with them.

CATV
Community Antenna Television.

CBP
Coded Block Pattern.

CBPY
Coded Block Pattern for luminance.

CBR
Constant Bit Rate. An operation in which the bit rate is constant from start to finish of the compressed bitstream.

CCD
Charge-Coupled Device. A type of silicon integrated circuit used to convert light into an electronic signal.

CCDC
Channel Compatible DigiCipher. An HDTV system proposed by the American Television Alliance, consisting of General Instruments and Massachusetts Institute of Technology.

CCETT
Centre Commun D'Etudes de Telecommunications et de Telediffusion.

CCITT
International Telegraph and Telephone Consultative Committee. A standardization body for telecommunications.

CD
Compact Disc.

CDMA
Code-division multiple access, based on spread-spectrum code assignments.

CDS
Correlated Double Sampling, a circuit commonly used to process the output signal from a CCD image sensor in order to reduce low-frequency noise components.

CEBus
Consumer Electronics Bus. A multimedia distribution system in the home.

CELP
Code-Excited Linear Predictive coding.

CFA
Color Filter Array. A mosaic or stripe layer of colored transmissive filters fabricated on top of an imager in order to obtain a color image from a single-image sensor.

CIDCW
Call Identification Delivery on Call Waiting (type II). A subscriber feature that allows for the display of the time, date, number, and other information about the caller to the called party while the called party is off-hook.

CIF
1. Common Intermediate Format.
2. Common Interleaved Frame, the serial digital output from the main service multiplexer, which is contained in the main service channel part of the transmission frame. It is common to all transmission modes and contains 55,296 bits (i.e. 864 Cus).

CISC
Complex Instruction Set Computer. A standard computing approach taken by Intel and MC68000 microprocessors.

CLASS
Custom Local-Area Signaling Service. A set of services and enhancements provided to customers that may include CND, CNAM, message waiting, and other features.

CLID
Calling Line Identification Delivery (type I). A subscriber feature that allows for the on-hook display of the time, date, number, and other information about the caller to the called party.

CMA
Constant Modulus Algorithm for updating tap-weight coefficients in blind equalization.

CMFSK
Coherent Multilevel Frequency Shift Keying.

CNAM
Calling Name delivery. A subscriber feature that allows for the display of the time, date, number, and name of the caller to the called party.

CND
Calling Number Delivery. A subscriber feature that allows for the display of the time, date, number, and other possible information about the caller to the called party.

CNET
Centre National d'Etudes de Telecommunications.

CO
Central Office. A main telephone office, usually within a few miles of a subscriber, that houses switching gear. Commonly capable of handling about 10,000 subscribers.

Coding
Also called compression or bit rate reduction, the process of taking a signal and reducing the number of bits, energy, time, or bandwidth necessary for its transmission. In the context of this chapter, coding refers specifically to bit rate reduction of a digitally captured or encoded signal.

Color Pixel Reconstruction
An algorithm that creates a fully populated color image record from the output of a CFA-type sensor by interpolating values for each color at each pixel location.

Contrast
A measure of the difference in intensity between two adjacent patches of light.

Convolution Coding
The coding procedure that generates redundancy in the transmitted data stream in order to provide ruggedness against transmission distortions.

CPE
Customer Premises Equipment, a term used to define a class of consumer devices found in the hope that connect to a public network. Examples include a set-top box, telephone, satellite receiver, personal computer with a modem, answering machines, and fax machines.

CPM
Continuous-Phase Modulation.

CPT
Call Progress Tones, DTMF tones sent while off-hook to signal-enhanced features.

CRC
Cyclic Redundancy Check, verifies the correctness of data.

CSO
Composite Second Order. A clustering of second-order frequency beats at 1.25 MHz above the visual carriers in cable systems.

CSPS
Constraint System Parameters Stream. An MPEG-2 program stream that conforms to the founds specified in the MPEG-2 system layer specification.

CT
Clock-Time and Date, Coordinated Universal Time (UTC) code can be used to set the clock to the exact time as displayed on the receiver.

CT2
Cordless Telephone-2. A second generation cordless telephone system introduced in Great Britain in 1989.

CTB
Composite Triple Beat. A clustering of third-order frequency beats around the visual carriers in cable systems.

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D

DAA
Data Access Arrangement. A CPE interface to network, complying with title 47, part 68 of the Code of Federal Regulations.

DAB
Digital Audio Broadcasting.

DAT
Digital Audio Tape.

DAVIC
Digital Audio-Visual Council. A nonprofit association whose purpose is to identify, select, augment, develop, and obtain the endorsement of formal standards bodies of specifications of interfaces, protocols, and architectures of digital audiovisual applications and services.

DBD
Displaced Block Difference.

DBS
Direct Broadcast Satellite. A digital system for sending/receiving an MPEG-2 transport stream providing audio/video and data services from a stationary satellite to a small receiving antenna.

DCC
Digital Compact Disc.

DCME
Digital Circuit Multiplex Equipment.

DCS 1800
Digital Communication System-1800, which is an extension of the Global System for Mobile Communications standard in the 1800-MHz band for personal communication networks.

DCT
Discrete Cosine Transform.

DDCR
Decision-Directed Carrier Recovery. A carrier recovery scheme that uses the decisions feedback from the receiver bit or symbol decision detection circuit.

DECT
Digital European Cordless Telephone. A cordless telephone standard developed by the European Telecommunications Standards Institute in 1992.

Depth of Field
The difference between the maximum and minimum distances from a camera to objects in a scene that can be captured in acceptably sharp focus.

DFE
Decision Feedback Equalizer. A nonlinear equalizer consisting of a feed-forward equalization filter and a feedback equalization filter.

Digital Camera
An electronic camera that captures images using a solid-state image sensor, and then outputs a digital signal representing the images or records the images on a digital storage medium.

DMC
Discrete memoryless channel, which is specified by the transition probabilities of input and output symbols.

DMT
Discrete multitone. A multicarrier modulation scheme.

DN
Directory Number.

DPCM
Differential Pulse Code Modulation.

DSC-HDTV
Digital Spectrum-Compatible HDTV. An HDTV system proposed by Zenith Electronics and AT&T in 1992.

DSM
1. Digital Storage Medium. A digital storage or transmission device or system.
2. Direct Sequence Modulation. A spread spectrum modulation scheme that directly modulates the information-bearing data with a spreading code sequence.

DSM CC
Digital Storage Medium Command and Control. A protocol intended to provide the basic control functions and operations specific to managing an MPEG-2 system bitstream on digital storage media.

DSP
Digital Signal Processor. An architecture, based on the Harvard machine, that uses separate data and instruction buses as well as certain instructions optimized for signal processing, such as multiply/accumulate.

DTMF
Dual-tone multifrequency, a tone-dialing system based on outputting two non-harmonic-related frequencies simultaneously to identify the number dialed or signal call progress. Eight frequencies have been assigned to the four rows and four columns of a typical keypad.

DTS
Decoding Time Stamp. A field that may be present in a PES packet header that indicates the time that an access unit is decoded in the system target decoder.

DTTB
Digital Television Terrestrial Broadcasting.

DVB
Digital Video Broadcasting.

DVD
Digital Versatile Disc. A high-density CD-ROM technology that provides capacity for full-length MPEG-2 movies as well as data and audio storage and playback. (Also called Digital Video Disc.)

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E

EBU
European Broadcast Union.

ECM
Entitlement Control Message. Private conditional access information that specifies authorization levels or the services of specific decoders.

Edge Enhancement
A signal-processing operation that accentuates edge details within an image to increase the apparent sharpness. Such operations may also be called aperture correction, sharpening, or peaking.

EIA
Electronic Industries Association. A standard-setting body for consumer electronics.

EIA-NRSC
Electronic Industries Association -- National Radio Systems Committee.

Ensemble
The transmitted signal comprising a set of regularly and closely spaced orthogonal carriers. The ensemble is the entity that is received and processed. In general, it contains program and data services.

EOB
End of Block.

EON
Enhanced Other-Networks Information. This feature can be used to update the information stored in a receiver about program services other than the one being received. Alternative frequencies, the PS name, traffic programs, announcement, identifications, and other information can be used to provide linkage to such other programs.

ES
Elementary Stream. A generic term for one of the coded video, coded audio, and other coded bit data in PES packets.

EWS
Emergency Warning System. This is intended to be used for the coding of audio and digital emergency and alerting messages. Such codes can be coordinated with national emergency and disaster agencies.

Exposure Determination
A method for setting the appropriate lens aperture and exposure time for a scene to be captured.

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F

FDCT
Forward DCT.

FDMA
Frequency-Division Multiple Access, based on frequency assignments.

FEC
Forward Error Correction.

FFT
Fast Fourier Transform.

FhG
Fraunhofer-Gesellschaft.

FHM
Frequency-Hopping Modulation. A spread-spectrum modulation scheme that is used to nonlinearly modulate a train of pulses with a sequence of pseudorandom frequency shifts.

FIB
Fast Information Block. A data burst of 256 bits. The sequence of FIBs is carried by the fast information channel. The structure of the FIB is common to all transmission modes.

FIC
Fast Information Channel. A part of the transmission frame (comprising the fast information blocks) that contains the multiplex configuration information, along with optional service information and data service components.

FIR
Finite Impulse Response. Commonly referring to an implementation structure of a filter.

FLC
Fixed-Length Coding.

FPLL
Frequency- and Phase-Locked Loop.

FSE
Fractionally Spaced Equalizer, whose tap spacing is a fraction of a data symbol duration.

FSK
Frequency-Shift Keying. FSK uses the data stream to modulate a carrier frequency.

Full-Frame Imager
A type of image sensor consisting of a single light-sensitive array of photoelements that also store the image during the sensor readout period.

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G

GA
Grand Alliance. A U.S. HDTV consortium consisting of General Instruments, Zenith Electronics, AT&T, David Sarnoff Research Center, Thomson Consumer Electronics, North Philips Electronics, and Massachusetts Institute of Technology.

Gamma Correction
A signal-processing operation that changes the relative signal levels in order to adjust the image tone reproduction, typically to correct for the nonlinear (nonunity gamma) light output-versus-signal input characteristic of the display. The relationship between the camera light input and the camera output signal level, called the optoelectronic conversion function (OCEF), provides the camera's gamma correction curve shape.

GBSC
GOB Start Code.

GMSK
Gaussian Minimum Shift Keying. A minimum shift keying with Gaussian frequency pulse shaping.

GOB
Group of Blocks.

GPS
Global Positioning System. A satellite ranging system based on direct sequence spread spectrum for mobile users to determine their location.

GSM
Global System for Mobile Communications. A second-generation cellular system standard set by the European Technical Standards Institute in 1990.

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H

HAS
Human Auditory System. The outer, middle, and inner ear along with the parts of the central nervous system that are involved in hearing, speech understanding, spatial localization, and other auditory functions.

HD-DIVINE
A Scandinavian digital terrestrial HDTV project proposed in 1991.

HDSL
High-speed Digital Subscriber Line, providing T1 rate services.

HDTV
High-Definition Television. An advanced digital television providing high resolution.

HFC
Hybrid fiber and coaxial network.

HVS
Human Visual System. The eye, optic nerve, visual cortex, and other parts of the central nervous system involved in seeing and interpreting images.

Hybrid Photography
A type of digital photography system in which original scenes are captured using traditional silver-halide-based photography, and the resulting film or prints are scanned to provide digital images that may be displayed, manipulated, transmitted, etc.

Hyperfocal Distance
The focus distance of a camera lens that offers the greatest depth of field. When a camera is focused at the hyperfocal distance, all objects from half the hyperfocal distance to infinity are within the camera's depth of field.

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I

I
In-phase Component.

ICI
Intercarrier Interference, associated with multicarrier modulation systems.

IDCT
Inverse DCT.

IEEE
Institute of Electrical and Electronics Engineers.

IH
In-House Application. Data used by the station for internal use. For example, IH could be used as a remote switch to turn on/off a remote transmitter site via the studio-to-transmitter link.

IM
Intermodulation, referring to distortions generated by nonlinear devices in a system.

Image Compression
A process that alters the way image data are encoded in order to reduce the average size of an image file.

Image Data Format
A specification for storing image data and related information in a digital file. One example is TIFF, tag image file format, which can be used to store various types of monochrome or color bit-mapped images.

Imaging Chain
A flow diagram that indicates all of the components used to produce a final image in a digital photography system.

Interlaced Scanning
A scanning process in which the distance from center to center of successively scanned lines is two or more times the nominal line width, and in which the adjacent lines belong to different fields.

Interline Sensor
A type of image sensor consisting of a two-dimensional array containing light-sensitive photoelements adjacent to light-shielded vertical storage registers.

Irrelevancy
The part of a signal that is not perceptible to the human user under the normal circumstances of use. In other words, irrelevancy is the part of the signal that may be removed at the encoder, and removed at the decoder, with no loss of content.

IRT
Institut fur Rundfunktechnik, Munchen (FRG).

IS
International Standard.

IS-54
Interim Standard-54. A dual mode standard for U.S. digital cellular system and Advance Mobile Phone Service based on time-division multiple access, set by EIA/TIA in 1990.

IS-95
Interim Standard-95. An air interface standard for U.S. code-division multiple access and Advance Mobile Phone Service dual-mode operation for mobile and cellular users.

ISDN
Integrated Services Digital Network. A communications network intended to carry digitized voice, data, and video services multiplexed onto the public network with rates up to 64 kb/s.

ISI
Intersymbol Interface. The additive contribution (interference) to a received sample from transmitted symbols other than the symbol to be transmitted.

ISM Bands
Industrial, Scientific, and Medical frequency bands 902-928 MHz, 2.4-2.4835 GHz, and 5.725-5.85 GHz.

ISO
International Organization of Standardization.

ITU
International Telecommunication Union. An intergovernmental organization responsible for setting global standards.

ITU-R
International Telecommunications Union-Radio Standardization Sector.

ITU-T
International Telecommunications Union-Telecommunications Standardization Sector.

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J

JDC
Japanese Digital Cellular.

JND
Just Noticeable Difference. The level at which an observer can begin to distinguish between an original signal and a noisy/corrupted/distorted signal. The JND is sometimes referred to as a threshold or perceptible threshold.

JPEG
Joint Photographic Experts Group.

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K

kb/s
Kilobits Per Second.

KLT
Karhunen-Loeve Transform.

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L

LE
Linear Equalizer. A linear filter that is used to reduce intersymbol interference.

LF
Loop Filter.

LFE
Low-Frequency Enhancement.

LMS
Least Mean Square. An algorithm for adaptively adjusting the tap coefficients of an equalizer based on the use of (noise-corrupted) estimates of the gradients.

LN
Location and Navigation. This feature gives the following information on station location: transmitter's state, city, latitude, and longitude (in the form of a computed grid number).

Loop
The loop formed by the two subscriber wires (tip and ring), connected to the telephone at one end and the central office (or PBX) at the other end. Generally, it is a floating system, not referred to ground or AC power.

LPC
Linear Predictive Coding. A particular form of redundancy removal, where a "linear predictor" is created to remove the redundancy due to vocal tract (or other signal generation) effects. LPC is commonly used in a speech coder because this method allows for good tracking of the redundancy introduced by the human vocal tract.

LT
Line Termination, generally CO line card.

LR
Location Register.

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M

M/S Mode
Mono/Stereo Mode.

MAE
Mean Absolute Error.

MAP
Maximum A Posteriori. A detection hypothesis that maximizes the a posteriori probability.

MB
Macroblock.

MBA
Macroblock Address.

Mbps
Megabits Per Second.

MC
Motion Compensation or Model Compliance.

MCBPC
Macroblock type and Coded Block Pattern for Chrominance.

MCI
Multiplex Configuration Information. Information defining the configuration of the multiplex. It contains the current (and in the case of an imminent reconfiguration, the forthcoming) details about the services, service components, subchannels, and the linking between these objects. It is carried in the FIC in order that a receiver may interpret this information in advance of the service components carried in the main service channel. It also includes identification of the ensemble itself and a date and time marker.

MCM
Multicarrier Modulation. A parallel digital modulation scheme that simultaneously modulates a number of carriers.

MDCT
Modified Discrete Cosine Transform.

ME
Motion Estimation.

MELP
Mixed-Excitation Linear Predictive coding.

Memory Card
A small, think, removable memory unit, containing digital integrated circuit memory chips, housed in a rugged package.

MIPS
Millions of Instructions Per Second. A measure of microprocessor throughput.

Mixed Signal
The combination of analog and digital circuits on the same semiconductor die.

MMDS
Multichannel Multipoint Distribution Service. A microwave local distribution system providing multiple television channel programs (up to 33 channels) to subscribers.

MMSE
Minimum Mean-Square Error.

MOD
Magneto-Optical Disk.

MPAC
Multichannel Perceptual Audio Coding (AT&T).

MPEG
Moving Pictures Expert Group.

MS
Mobile Station.

MSC
1. Mobile Switching Center.
2. Main Service Channel. A channel that occupies the major part of the transmission frame and carries all the digital audio service components, along with possible supporting and additional data service components.

MSE
Mean Square Error.

MSK
Minimum Shift Keying. A special case of continuous phase-FSK wherein the peak frequency deviation is equal to half the bit rate, which is the minimum frequency spacing for two frequency-shift keying signals.

MTF
Modulation Transfer Function. A representation of the human visual system's response to visual stimuli at various frequencies.

MV
Motion Vector.

MVD
Motion Vector Data.

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N

NBC
Non-Backward Compatibility.

NCMFSK
Noncoherent Multilevel Frequency Shift Keying.

NMR
Noise-to-Mask Ratio.

Noiseless Coding
Coding methods that do not remove any information present in the signal, i.e., that allow for perfect reconstruction of the original digital input signal. The classic set of noiseless coders are the information-theoretic coders such as Juffman coders. Ziv-Lempel coders, and arithmetic coders. However, other coders -- including subband, transform, and other source coders -- can be used as noiseless coders in some circumstances. A particular example is lossless JPEG.

NT
Network Termination. A connection between terminal equipment (TE) and the network.

NT1
Converts two-wire U-interface to four-wire S/T interface.

NTSC
National Television System Committee. The term also refers to the current U.S. color television system, which was specified and developed in 1950-1953.

NVOD
Near Video-On-Demand.

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O

OBO
Output Back-Off. The output power of a power amplifier in a modulation system that is needed to back off from the saturation point of the amplifier to avoid nonlinear distortion.

OFDM
Orthogonal Frequency Division Modulation or Multiplexing. A multicarrier modulation scheme that involves multiplexing a number of low-speed modulated carriers for transmission.

Off-Hook
The condition in which the telephone is connected to the phone system, permitting loop current to flow. The central office detects the DC current as an indication that the phone is busy.

On-Hook
The condition in which the telephone's DC path is open and no DC loop current flows. The central office regards an on-hook phone as available for ringing.

Optical Prefilter
An optically transmissive device, such as a stack of birefringent quartz plates, that limits the high-frequency content of an image focused on a solid-state image sensor in order to reduce aliasing.

OQPSK
Offset Quadrature Phase-Shift Keying, where on quadrature arm is offset by one bit duration relative to the other arm.

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P

PABX, PAX
Private Automatic Branch Exchange. A customer-owned, switchable telephone system providing internal and/or external station-to-station dialing.

PAC
Perceptual Audio Coding (AT&T).

Packet
1. A group of binary digits that is switched as a composite whole with data, control, and error elements arranged in a specified format.
2. A packet consists of a header followed by a number of contiguous bytes from an elementary data stream.

Packet Mode
The mode of data transmission in which data are carried in addressable blocks called packets. Packets are used to convey MSC data groups within a subchannel.

PACS
Personal Access Communication System. A third-generation personal communications system originally developed and proposed by Bellcore in 1992; it later became a radio interface standard for U.S. Personal Communications Service in the 1920-1930-MHz band.

PAD
Program-Associated Data. Information that is related to the audio data in terms of contents and synchronization. The PAD field is located at the end of the DAB audio frame.

PAL
Phase-Alternating Line.

PAM
Pulse Amplitude Modulation. A digital amplitude-modulation scheme.

PAR
Peak-to-Average power Ratio (usually expressed in decibels [dB] that is used to determine the robustness of a modulated signal against nonlinear distortion.

PASC
Precision Audio Subband Coding (Philips).

PAT
Program Association Table. Provides the association between a program number and the PID value of the transport stream packets, which carry the program definition.

Payload
A generic term referring to the bytes that follow the header bytes in a packet.

PCM
Pulse Code Modulation.

PCMCIA
Personal Computer Memory Card Industry Association. A nonprofit trade association founded in 1989 to define a standard memory card interface for computers.

PCR
Program Clock Reference. A time stamp in the transport stream from which decoder timing is derived.

PCS
Personal Communication Systems or Services.

PDC
Pacific Digital Cellular. A cellular standard that was developed in 1991 to provide for needed capacity in congested cellular bands in Japan.

Perceptual Coding
A lossy form of coding where parts of the signal that are not perceptible to the end user are removed. Perceptual coding is always lossy and is in some sense the dual of source coding, i.e., "destination coding," where information important to the destination (human being) is preserved and information not important is removed.

PES
Packet Elementary Stream. Consists of PES packets, all of whose payloads consist of data from a single elementary stream, and all of which have the same stream identifier.

PFD
Phase and Frequency Detector used for decision-directed carrier recovery.

Photo CD Disc
A compact disc-recordable (CD-R) optical write-once disc that stores scanned photographic images using the Image Pac image data format.

PHS
Personal Handy Phone System. A Japanese air interface standard set by the Research and Development Center for Radio Systems; its network interface was specified by the Telecommunications Technical Committee of Japan in 1993.

PI
Program Identification. This information consists of a code that enables a receiver to identify the program. The code is not intended for direct display to the user, rather it is sort of a program ID to allow distinction from all other programs. This is valuable for "scanning" and "learning" receivers (with or without memory), which are equipped to switch over to an alternate transmitter with the same program (NPR radio affiliates, for example, often broadcast the same program at the same time).

PID
Packet Identifier. A unique integer value used to associate elementary streams of a program in a single or multiple program MPEG-2 transport stream.

PIN
Program Item Number. A number that can be used by a "smart radio" to tune a specific program at a particular time when the program has come on the air. It allows for consumer convenience in receiving special programs.

Pixel, Pel, Picture Element
The smallest area of a television picture capable of being delineated by an electric signal passed through the system or part of it.

PMT
Program Map Table. Provides the mappings between program numbers and the elementary streams that make up the program.

POTS
Plain Old Telephone Service.

PRA
Pel Recursive Algorithm.

Program
A collection of elementary streams with a common time base.

PS
Program Service. This is a text of not more than eight alphanumeric characters coded in conformity with the standard and used to display the service name of the broadcasters. Examples of PS names are "WABC," "WXYZ," "G-100," "HOT93," or "COOL99".

PTY
Program Type. This is an identification number to be transmitted with each program; it will identify the "type" or "category" of the program content. There are 31 codes allowed and in the RBDS U.S. standard, 22 categories plus emergency alert have been decided on. 15 is for classical music, and the display will show "CLASSICL" -- lacking the "A" because only eight characters are allowed.

PTYN
Program-Type Name. An alternate name to be displayed after the PTY search if the broadcaster wants to give a more specific music format.

Progressive (Sequential) Scanning
A rectilinear scanning process in which the distance from center to center of successively scanned lines is equal to the nominal line width.

PS
Program Stream. Consists of contiguous PES packets that comprise one or more video or audio elementary streams.

PSI
Program-Specific Information. Consists of normative data necessary for the demultiplexing of transport streams and the successful regeneration of programs.

PSI-CELP
Pitch-Synchronous Innovation Code Excited Linear Predictive coding.

PSK
Phase-shift keying. A digital phase-modulation scheme.

PSNR
Peak Signal-to-Noise Ratio.

PSTN
Public Switched Telephone Network.

PTS
Presentation Time Stamp. A field that may be present in a PES packet header that indicates the time that a presentation unit is presented in the system target decoder.

PU
Presentation Unit. A decoded audio frame or a decoded picture.

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Q

Q
Quadrature component.

QAM
Quadrature-Amplitude Modulation. A combined phase- and amplitude-modulation scheme that is used to modulate the carrier signal in phase quadrature.

QCELP
Qualcomm Code Excited Linear Predictive coding.

QCIF
Quarter CIF.

QPSK
Quadrature or Quaternary Phase-Shift Keying. A digital phase-modulation scheme that is used to modulate the carrier signal in phase quadrature.

Quantization
A process by which information, redundancy, and irrelevancy are removed from a signal. A quantizer is a construct that takes an amplitude-continuous signal and converts it to discrete values that can be reconstructed by a decoder.

Quantize
To subdivide the range of values of a variable into a finite number of nonoverlapping subranges or intervals, each of which is represented by an assigned value within the subrange.

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R

Random Access
The process of beginning to read and decode the coded bitstream at an arbitrary point.

Redundancy
Parts of a signal that are, because of the process(es) that generated it, predictable or in some way related to other parts of the same signal. In a strict sense, redundancy in a signal is not part of the information content of that signal as it may be removed at the encoder, and restored at the decoder, with no loss of content.

RF
Radio frequency that is above the audio and below infrared frequencies. The frequency range is 10 kHz to 10 GHz, allocated for radio use.

Ring
One of the two wires connecting the central office to CPE. The name derives from the ring portion of the plugs used by operators in older equipment to make the connection. Ring is traditionally negative with respect to tip.

RISC
Reduced Instruction Set Computer. A CPU architecture that optimizes processing speed by using a smaller number of basic machine instructions.

RJ-11
Standard four-wire analog phone connector.

RJ-45
Standard eight-wire ISDN connector.

RP
Radio Paging. The RP feature is intended to provide for numeric and alphanumeric paging via the FM radio transmitter. Already, several international paging operations are in progress. RDS paging receivers are not unlike those already in the marketplace; they are merely operating at a different frequency and from an already installed transmitter.

RPE-LTP
Regular Pulse Excited linear predictive coding with Long-Term Prediction.

RT
Radiotext. For receivers suitably equipped with a display, messages could be sent to the listener giving information about the program being broadcast or advertiser-supported messages. A voice synthesizer could be controlled by the radiotext code, for example, to enunciate a certain message in the absence of a display.

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S

S/T Interface
Four-wire interface between terminal equipment (TE) and network termination (NT).

SCM
Single-carrier modulation, in which information data is modulated on one carrier for transmission.

SCR
System Clock Reference. A time stamp in the program stream from which decoder timing is derived.

Scrambling
The alteration of the characteristics of a video, audio, or coded data stream in order to prevent unauthorized reception of the information in a clear form.

SCTE
Society of Cable Telecommunications Engineers.

SCWID
Spontaneous Call-Wire Identification Delivery (type II) -- see CIDCW.

SECAM
Sequentiel Couleur Avec Memoire.

SER
Symbol Error Rate. A measure of probability of symbol errors in a communication system.

SFN
Single-Frequency Network. A network of DAB transmitters sharing the same radio frequency to achieve a large-area coverage.

Signaling
The transmission of control or status information in the form of dedicated bits or channels of information inserted on lines with voice data.

Simultaneous Contrast
A measure of the perceived difference between two adjacent patches of light.

SLM
Signal Level Meter.

SMPTE
Society of Motion Picture and Television Engineers.

SMR
Signal-to-Mask Ratio.

SNR
Signal-to-Noise Ratio. The measure of the energy in the signal (usually expressed in decibels [dB]), within a certain bandwidth and/or time, versus the energy of the noise that was added to the signal by some process. In this context, noise refers not only to added random noise but to any other difference, other than simple scaling, present in the reconstructed signal. In video, a variant of SNR called PSNR (peak signal-to-noise ratio) is often used; this corresponding to the energy of the noise versus the maximum possible signal energy.

SONET
Synchronous Optical Network, which specifies data transmission over optical fiber with rates ranging from 51.84 Mb/s to 9.95 Gb/s.

Source Coding
Techniques that use the redundancy in a signal to reduce the bit rate. Some source coders (noiseless coders) remove only redundancy and provide perfect reconstruction of the decoded signal. Tohers remove redundancy and some information as well and provide a noisy decided signal, but usually with unobjectionable noise characteristics. Typical kinds of source coding are LPC, ADPCM, CELP, subband, and transform.

SPA
Significant pel area.

Splicing
The concatenation, performed on the system level, of two different elementary streams. The resulting system stream conforms totally to the MPEG-2 system standard. The process may result in discontinuities in time base and decoding.

SSM
Spread-spectrum modulation. A digital modulation scheme that spreads the system bandwidth far greater than the minimum required bandwidth.

Start Code
A 32-bit code word embedded in the coded bitstream that is unique. The start codes are used for several purposes, including identifying some of the layers in the coding syntax, and they consist of a 24-bit prefix (0x000001) and an 8-bit stream ID.

STD
System Target Decoder. A hypothetical reference model of a decoding process used to describe the semantics of the MPEG-multiplexed bitstream.

Stream ID
Stream Identifier. An 8-bit unique word used to define a video, an audio, or other PES packet.

Stream Mode
The mode of data transmission within the Main Service Channel, in which data are carried transparently from source to destination. Data are carried in logical frames.

Subband
A subdivision of the audio frequency range. In the audio coding system, 32 subbands of equal bandwidth are used.

Subchannel
A part of the main service channel that is individually convolutionally encoded and comprises an integral number of capacity units per common interleaved frame.

SVF
Still Video Floppy. A standardized recording medium for analog electronic still cameras developed in the early 1980s. SVF cameras use a 2-inch-diameter floppy disk capable of storing either 50 field images or 25 frame images.

Synchronization Channel
A part of the transmission frame provided to ensure proper time, frequency, and phase synchronization in the receiver.

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T

TA
1. Terminal Adapter. Takes a non-ISDN data stream and converts it to the ISDN data format; used to provide S/T or U-interface connection to type 2 terminal equipment (non-ISDN-compliant).
2. Traffic-Announcement Identification. This is an indicator to show when the actual traffic announcement is in progress. It can be used by the receiver to switch from its current mode over to the traffic announcement on the main audio channel, and then back to the previous setting after the traffic announcement concludes.

TCE
Thomson Consumer Electronics.

TCM
Trellis-Code Modulation. A combined coding and modulation technique.

TDC
Transparent Data Channel. These channels could be used to send alphanumeric characters, or other text, or for transmission of computer program data or similar information not intended to display on the user's set.

TDMA
Time-Division Multiple Access. A time-slot-based multiuser access scheme.

TE
Terminal Equipment. Type 1 (TE1) is ISDN-compliant. Type 2 (TE2) requires a terminal adapter to connect to the network.

Telephone Bandwidth
Usually 200 Hz to 3200 Hz, although some algorithms and transmission facilities provide signals from 50 Hz to 3600 Hz, depending on the situation and equipment involved.

THM
Time-Hopping Modulation. A spread-spectrum technique using pseudorandom time-hop patterns as the spreading sequence code; it is analogous to pulse-position modulation.

TIA
Telecommunication Industry Association. A trade organization that provides services such as government relations, market activities, educational programs, and standards-setting activities.

Time Stamp
Indicates the time of an event such as the arrival of a byte or the presentation of a presentation unit.

Tip
One of the two wires connecting the central office to SPE. The name derives from the tip of the plugs used by operators in older equipment to make the connection. Tip is traditionally positive with respect to ring.

TMN
Test Model for Near-term solution (H.263).

TOV
Threshold of Visibility. A bit-error-rate HDTV threshold of 3 x 10-6, at which value the impairment effect first becomes visible in the picture.

TP
Traffic-Program Identification. This is a digital flag sent by the broadcaster to turn on the lamp or other signal within the receiver to indicate to the user that the broadcaster is giving traffic announcements (when the lamp does not light, it means that the station is not giving traffic announcements at the time).

TR
Timing Recovery for symbol synchronization.

Transmission Frame
The actual transmitted frame -- specific to the three transmission modes -- conveying the synchronization channel, the fast information channel, and the main service channel.

Transmission Mode
A specific set of transmission parameters (e.g., number of carrier, OFDM symbol duration). Three transmission modes (i.e., I, II, III) are defined to allow the system to be used for different network configurations and a range of operating frequencies.

TS
Transport Stream. Contiguous packets, each of which is 188-bytes in length, consisting of one or more PES packets.

TTIB
Transparent Tone In Band. A pilot-aided carrier recovery technique.

U

UEP
Unequal Error Protection.

U-Interface
A two-wire interface between network termination (NT) and line termination (LT).

U-TA
U-interface Terminal Adapter. Converts non-ISDN data stream to ISDN data format; used to provide U-interface connection to type 2 terminal equipment in North America.

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V

VAR
Variance.

VBR
Variable Bit Rate. An operation in which bit rate varies with time during the decoding of a compressed bitstream.

VCR
Videocassette Recorder.

VLC(D)
Variable Length Coding (Decoding).

VLIW
Variable-Length Instruction Word. A new CPU architecture that relies on a variable-length word size and small parallel processors to provide throughput in terms of billions of operations per second.

VOD
Video On Demand.

VSB
Vestigial Sideband. The transmitted portion of one sideband; the sideband is suppressed in a transmitter having a gradual cut-off in the neighborhood of the carrier frequency. Meanwhile, the other sideband is transmitted without suppression.

VSELP
Vector-Sum Excited Linear Predictive coding.

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W

WACS
Wireless Access Communication System. Developed to provide wireless connections for local exchange carriers.

White Balance
A process for adjusting the relative signal levels of the red, green, and blue channels from a camera to correct for the color of the light source illuminating a scene, so that objects that appear to be white in the scene are reproduced as white on the soft-display or hard-copy print.

Wideband Speech
Speech having a bandwidth of 60 Hz to 7 kHz, also referred to as commentary grade or remote contribution quality.

WLAN
Wireless Local-Area Network.

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