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AC3 AC-3
Audio compression standard adopted by ATSC and owned by Dolby.
American National Standards Institute
Application Program Interface. Typically command based
Address Resolution Protocol. A standard method for finding hardware addresses from network layer addresses such as the Internet Protocol (IP).
American Standard Code for Information Interchange
Asynchronous Serial Interface. A standard DVB interface for a transport stream.
Asynchronous Transfer Mode
Advanced Television Systems Committee. Digital broadcasting standard developed in North America.
Time space provided to cable operators by cable programming services during a program for use by the CATV operator; the time is usually sold to local advertisers or used for channel self promotion.
B Frames
Bi-directionally predicted pictures, or pictures created from references to past and future pictures
The rate at which a bit stream arrives at the input of a decoder
Someone who provides a sequence of scheduled events or programs to the viewer.
Conditional Access. This system allows service providers to control subscriber access to programs and services via encryption.
Conditional Access Table. This table identifies EMM streams with a unique PID value. The CAT is always found on PID 0x0001
Community Access Television, otherwise known as Cable TV
Constant Encoded Bit Rate
CC Data, Closed Captioning Data. Data that can be displayed as text on a television or video screen to provide additional or interpretive information to viewers who wish to access it
A Channel is a synonym for a “Service” in DVB terminology, or a “Program” in MPEG terminology
Command-Line Interface. A mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks. This is text only.
Reduction of the number of bits needed to represent an item of data
Cyclic Redundancy Check. This 32-bit field is used to verify the correctness of table data before decoding
Cable Virtual Channel Table. This ATSC table describes a set of one or more channels using a number or name within a cable network. Information in the table includes major and minor numbers, carrier frequency, short channel name, and information for navigation and tuning. This table is located on PID=0x1FFB
Transforming encoded information into information that is readable to a program or a user.
Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network
Domain Name System. A hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participants. Most importantly, it translates domain names meaningful to humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide
Digital Television. A general term used to describe television that has been digitized. It can refer to Standard-definition TV or High-definition TV
Digital Video Broadcasting. The DVB Project is a European consortium that has standardized digital TV broadcasting in Europe and in other countries.
Digital Video Broadcasting-Cable. The DVB standard for broadcasting digital TV signals by cable. The RF spectrum in digital cable TV networks has a frequency range of (approx) 46MHz to 850MHz.
Digital Video Broadcasting-Satellite. The DVB standard for broadcasting digital TV signals via satellite.
Digital Video Broadcasting-Terrestrial. The DVB standard for broadcasting digital terrestrial TV signals.
Entitlement Control Message. ECMs carry private conditional access information that allows receivers to decode encrypted information.
Event Information Table. This table is part of the ATSC PSIP. It carries the TV guide information including titles and start times for events on all the virtual channels within the transport stream. ATSC requires that each system contain at least 4 EIT tables, each representing a different 3-hour time block. The PIDs for these tables are identified in the MGT.
EIT Actual (DVB)
Event Information Table. This table is part of the DVB SI. It supplies the list of events corresponding to each service and identifies the characteristics of each of these events. Four types of EITs are defined by DVB : 1) The EIT Actual Present/Following supplies information for the present event and the next or following event of the transport stream currently being accessed. This table is mandatory and can be found on PID=0x0012. 2) The EIT Other Present/Following defines the present event and the next or following events of other transport streams in the system that are not currently being accessed by the viewer. This table is optional. 3) The EIT Actual Event Schedule supplies the detailed list of events in the form of a schedule that goes beyond what is currently or next available. This table supplies a schedule of events for the transport stream currently being accessed by the viewer. 4) The EIT Other Event Schedule supplies the detailed schedule of events that goes beyond what is currently or next available. This table supplies a schedule of events for other transport streams in the system that is not currently being accessed by the viewer. The EIT Schedule tables are optional.
Entitlement Management Message. EMMs specify authorization levels or services of specific decoders. They are used to update the subscription options or pay-per-view rights for an individual subscriber or for a group of subscribers.
The process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key
Electronic Program Guide. This guide represents a broadcasting data structure that describes all programs and events available to the viewer. It functions like an interactive TV guide that allows users to view a schedule of available programming and select what they want to watch.
Elementary Stream. A bit stream that includes video, audio or data. It represents the preliminary stage to the Packetized Elementary Stream (PES)
A popular standard (or protocol) for linking computers into a local area network. Popular speeds can range between 10 Mbps and 100 Mpbs
Forward Error Correction. This method adds error control bits before RF modulation. With these bits, errors in the transport stream may be detected and corrected prior to decoding
A part of a computer system or network that is designed to block unauthorized access while permitting authorized communications
A term often used to denote the fixed, usually rather small, programs and data structures that internally control various electronic devices. Usually resides directly on the device.
Lines of spatial information for a video signal
File Transfer Protocol. A standard network protocol used to exchange and manipulate files over a TCP/IP based network, such as the Internet
See Group Of Pictures
Group of Pictures
a set of pictures usually 12-15 frames long used for temporal encoding of MPEG-2 video.
Graphical User Interface. A type of user interface item that allows people to interact with programs in more ways than typing. Offers graphical icons, and visual indicators, as opposed to text-based interfaces, typed command labels or text navigation to fully represent the information and actions available to a user
High Definition
High Definition Television. HDTV’s resolution is approximately twice as high as that of Standard Definition Television (SDTV) for both horizontal and vertical dimensions. HDTV has an aspect ratio of 16x9 as compared to the 4x3 aspect ratio of SDTV.
I Frame
Intra-coded frame, or a picture encoded without reference to any other picture. I-frames provide a reference for Predicted and Bi-directionally predicted frames in a compressed video stream.
International Electrotechnical Commission
Institute of Electrical and Electronics Engineers.
Internet Group Management Protocol (IGMP) is a communications protocol used to manage the membership of Internet Protocol multicast groups. IGMP is used by IP hosts and adjacent multicast routers to establish multicast group memberships
Integrated Receiver Decoder. This is a receiver with an MPEG-2 decoder, also known as a set-top box.
International Standardization Organization
Internet service provider (also called Internet access provider, or IAP) A company that offers its customers access to the Internet
Local Area Network. A computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport
MAC Address
Media Access Control Address. A unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification, and used in the Media Access Control protocol sublayer
Macro Block
A group of 16x16 pixels used for motion estimation in temporal encoding of MPEG-2 video
Mega Bits Per Second
Master Guide Table. This table is part of the ATSC PSIP. It defines sizes, types, PIDs, and version numbers for all of the relevant tables within the transport stream. The PID value for this table is 0x1FFB.
Hidden Adtec API command. *.sysd mohj .
Main Profile at High Level. MPEG-2 specifies different degrees of compression vs. quality. Of these, Main Profile at High Level is the most commonly used for HDTV
Main Profile at Main Level. MPEG-2 specifies different degrees of compression vs. quality. Of these, Main Profile at Main Level is the most commonly used
Moving Picture Experts Group, also called Motion Picture Experts Group
Multi-Protocol Label Switching. An operating scheme that is used to speed up the flow of traffic on a network by making better use of available network paths
Multiple Program Transport Stream. An MPEG-2 transport stream containing several programs that have been multiplexed.
(n ) — A digital stream including one or more services in a single physical channel. (v)—To sequentially incorporate several data streams into a single data stream in such a manner that each may later be recovered intact.
Network Address Translation. The process of modifying network address information in datagram packet headers while in transit across a traffic routing device for the purpose of remapping a given address space into another
National Cable Television Association
Net Sets
Network Settings. Cue definitions for insertion
Network Interface Controller. A hardware device that handles an interface to a computer network and allows a network-capable device to access that network
The standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7.
Network Time Protocol
National TV Standard Committee Color TV System (USA and 60 Hz countries)
Opersting System. An interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine.
P Frame
Predicted frame, or a picture coded using references to the nearest previous I- or P- picture
See Transport Packet.
Phase Alternating Line.
Program Association Table. This MPEG-2 table lists all the programs contained in the transport stream and shows the PID value for the PMT associated with each program. The PAT is always found on PID 0x0000.
All the bytes in a packet that follow the packet header
Pulse-code modulation
Program Clock Reference. A time stamp in the transport stream that sets the timing in the decoder. The PCR is transmitted at least every 0.1 seconds
PES Packet
The structure used to carry elementary stream data (audio and video). It consists of a header and a payload.
PES Packet Header
The leading bytes of a PES packet, which contain ancillary data for the elementary stream.
Packet Identifier. This unique integer value identifies elements in the transport stream such as tables, data, or the audio for a specific program
Program Map Table. This MPEG-2 table specifies PID values for components of programs. It also references the packets that contain the PCR.
See Service
Program Specific Information. PSI refers to MPEG-2 table data necessary for the demultiplexing of a transport stream and the regeneration of programs within the stream. PSI tables include PAT, CAT, PMT and NIT.
Program and System Information Protocol. The ATSC protocol for transmission of data tables in the transport stream. Mandatory PSIP tables include MGT, STT, RRT, VCT and EIT
Quadrature Amplitude Modulation. This is a type of modulation for digital signals used in CATV transmission (DVB-C). Amplitude and phase of a carrier are modulated in order to carry information.
Quality Control
Removable Screw Terminal Also known as a Phoenix Connector
Real-Time Transport Protocol. Provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not address resource reservation and does not guarantee quality-of-service for real-time services
Real Time Streaming Protocol. A network control protocol for use in entertainment and communications systems to control streaming media servers. The protocol is used to establish and control media sessions between end points
Sampling Frequency
See Sampling Rate / Sample Rate
Sampling Rate / Sample Rate
The number of samples per second (or per other unit) taken from a continuous signal to make a discrete signal. For time-domain signals, it can be measured in samples per second (S/s), or hertz (Hz).
Schedule Break
Avail or an actual insertion in progress
Society of Cable Telecommunication Engineers
Standard Definition
Serial digital interface
Service Description Table. This DVB SI table describes the characteristics of available services. It is located on PID 0x0011. Two types of SDTs are specified by DVB, the SDT Actual and the SDT Other. The SDT Actual is a mandatory table that describes the services within the transport stream currently being accessed. The SDT Other describes the services contained in other transport streams in the system.
A syntactic structure used for mapping PSI/SI/PSIP tables into transport packets of 188 bytes.
A collection of one or more events under the control of a single broadcaster. Also known as a Program.
Society of Motion Picture and Television Engineers.
Satellite News Gathering. This refers to the retransmission of events using mobile equipment and satellite transmission.
Simple Network Management Protocol. This is the standard protocol for system and network administration
Splice Point
A point in a PID stream that is either an Out Point or an In Point
Single Program Transports Stream. An MPEG-2 transport stream that contains one unique program.
Secure Shell. A network protocol that allows data to be exchanged using a secure channel between two networked devices. Used primarily on Linux and Unix based systems to access shell accounts
Set-top box. A digital TV receiver (IRD).
System Time Table. An ATSC PSIP table that carries time information needed for any application requiring schedule synchronization. It provides the current date and time of day and is located on PID 0x1FFB.
Service Information is transmitted in the form of tables, which are further divided into subtables, then into sections, before being transmitted. Several types of tables are specified by MPEG, DVB and ATSC. Refer to the Pocket Guide for more information on the different types of Service Information tables and their functions.
Transmission Control Protocol. A connection-oriented protocol that is widely used in Internet communications
TOT - Time Offset Table. This optional DVB SI table supplies the UTC time and date and shows the difference between UTC time and the local time for various geographical regions. The PID for this table is 0x0014.
Trans(mitter) and (res)ponder. This refers to the equipment inside a satellite that receives and re-sends information.
Transport Packet
188-byte packet of information in a transport stream. Each packet contains a header and a payload
Transport Stream
A stream of 188-byte transport packets that contains audio, video and data belonging to one (SPTS) or several (MPTS) programs.
Time to live. A limit on the period of time or number of iterations or transmissions in computer and computer network technology that a unit of data (e.g. a packet) can experience before it should be discarded
Terrestrial Virtual Channel Table. This ATSC table describes a s4t of one or more channels or services using a number or name within a terrestrial broadcast. Information in the table includes major and minor numbers, short channel name, and information for navigation and tuning. This table is located on PID=0x1FFB.
Communication link from earth to a satellite.
Universal Time, Co-ordinated.
Variable Encoding Bit Rate
Virtual Channel Table. This ATSC table describes a set of one or more channels of services. The formation in the table includes major and minor numbers, short channel name, and information for navigation and tuning. There are two types of VCTs, the TVCT for terrestrial systems and the CVCT for cable systems.
Video on Demand.
Vestigial Sideband Modulation. This is the terrestrial modulation method used in ATSC. It can have either 8 (8VSB) or 16 (16 VSB) discrete amplitude levels.


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