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ATSC Advanced Television Systems Committee

An international, non-profit organization developing voluntary standards for digital television. The ATSC member organizations represent the broadcast, broadcast equipment, motion picture, consumer electronics, computer, cable, satellite, and semiconductor industries.

BAT Bouquet Association Table

Provides information regarding bouquets (collections of services marketed as a single entity)

CAT Conditional Access Table

Used with EMM data to control conditional access to programs. This is used for pay television and similar services. DVB uses two types called multicrypt, which currently uses a PCMCIA card.

CBR Constant Bit Rate

Refers to video or audio encoding where the bitrate used doesn't fluctuate

CM Component Missing

Audio PID signaled incorrectly; Loss of audio or EPG on one program

DSM Digital Storage Medium

These commands provide control of a local digital storage medium, such as CD-ROM or hard disk

DTS Decoder Time Stamp

Is used in audio / video streams at the receiving end, where it is used to synchronize a set of elementary streams and control the rate at which they are replayed by the receiver

DVB Digital Video Broadcast

Name given to a world-wide imitative to replace the current analog based television systems with a digital service.

DVB-SI Tables Digital Video Broadcast-Service Information

ECM Entitlement Control Message

Coupled with the EMM, provides the communication channels for the controlled access to programs either through smart cards or through the use of PIN numbers. For example, a subscriber can ring a supplier, give a credit card number to access a particular program or service and the access code or encryption key can be sent to the decoder via one of these messages.

EIT Event Information Table

Describes the network events associated with each channel listed in the VCT. Provides a description, start time and duration. Used to create EPG

EPG Electronic Program Guide

An interactive, electronic equivalent of a printed television program guide and is used with digital set top boxes and television sets to list scheduled programs

ES Elementary Stream

The output of an audio or video encoder. ES contains only one kind of data, e.g. audio, video or closed caption. An elementary stream is often referred to as "elementary", "data", "audio", or "video" bitstreams or streams. The format of the elementary stream depends upon the codec or data carried in the stream, but will often carry a common header when packetized into a packetized elementary stream.

ETM Embedded Trace Macrocell

A hardware macrocell that, when connected to a processor, outputs trace information on a trace port. The ETM provides processor driven trace through a trace port compliant to the ATB protocol. An ETM always supports instruction trace, and might support data trace.

ETT Extended Text Table

Carries messages describing channels or events that provide more detailed information than the EIT. The messages appear as additional information in the EPG

MGT Master Guide Table

Acts as an index for all other tables (table sites, version numbers & PID value)

MPEG Motion Picture Experts Group

Since 1988 MPEG has been a working committee that defines and develops industry standards for coding audio visual information. These standards specify the data compression and transmission format and how they are delivered on digital broadcast systems

MUX Multiplexer

A multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line.

Null Packet

When carrying MPEG-2 or MPEG-4 video via MPEG-2 Transport Streams, something called Null Packets are regularly inserted by encoders and distribution systems. These Null Packets are inserted for many reasons and sometimes for no reason at all. One reason they are inserted is to pad-up variable bit rate content so as to produce a constant bit rate transport stream.

What is an MPEG Null Packet? It is a regular sized MPEG transport stream packet of 188 bytes in length with a few header bits set so to indicate that the contents of the remaining 184 bytes is meaningless. Null packets are not permitted to contain the PCR timing fields used for synchronization.

NIT Network Information Table

Shows the physical organization and characteristics of the network

PAT Program Association Table

The entry point for Program Specific Information (PSI); Moving Pictures Experts Group 2 (MPEG-2) data that identifies what parts of a stream belong to a particular program. The PAT is always carried in packets with a packet ID (PID) that equals 0. Packets in the same elementary stream all have the same PID and the decoder can select the elementary stream or streams it wants and reject the remainder. Each entry in the PAT points to a Program Map Table (PMT) that lists the elementary streams making up each program. Also carried in the metadata is the information that some programs will be open and some may be subject to encryption.

PCI Peripheral Component Interconnect

Defines the electrical characteristics and signal protocol used for two devices to communicate over a computer's central bus. PCI network adapters and other devices exist in several different shapes and sizes called "form factors."

PCR Program Clock Reference

Decoders use the re-generated system time clock to ensure that the decoding process is synchronized with the encoding process

PCR Jitter

Term used to name some aspects of frequency instability. The difference between the actual value of the PCR time stamped by the encoder and the expected value of the PCR, calculated by the decoder based on the clock rate and the time at which the PCR value is received.

PCR_AC Accuracy

Errors in the PCR values relative to its position in the transport stream; Independent of transmission method (explicitly not a real time measurement

PCR_DR Drift Rate

The speed of the slow variations (wander)

PCR_FO Frequency Offset

To determine the frequency offset, the frequency is measured and compared with the theoretical 27 MHz system frequency

PCR_OJ Overall Jitter

Systematic jitter arises primarily because of the repetition rate of the transport stream packets on the PID containing PCR

PEC Packet Error Code

A server responds to a request that has problems by sending the packet back and including an error packet. Each error has a code, type, error …

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

PMT Program Map Table

Maintans the links between the program number and the packet identifiers so that the packetized information can be identified and linked to the other packets to create programs. Without this information, the decoder cannot cope with multiple programs.

POA Program Off Air

PMT Incorrect; Loss of one program in the Multiplex

PSI Program Specific Information

Metadata about a program (channel) and part of an 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)

PSIP Program and System Information Protocol

Defines virtual channels and content ratings, as well as electronic program guides with titles and (optionally) descriptions to be decoded and displayed by the ATSC tuner.

PTS Presentation Time Stamp

A metadata field in an MPEG transport stream or MPEG program stream that is used to achieve synchronization of programs' separate elementary streams (for example Video, Audio, Subtitles) when presented to the viewer.

QoS Quality of Service

PAT timing exceeds limits; Slow channel change time

RRT Rating Region Table

Content ratings for each country (region) covered by the station, save the U.S., as that region is loaded into TV sets already

RST Running Status Table

Gives the status of an event (running or not running)


SCTE-142 classifies errors in five distinct levels. By identifying five levels of error severity, as opposed to just three priorities used by the TR 101-290 standard, SCTE-142 enables practical filtering and display only of errors that require immediate attention

SDT Service Description Table

Contains information about the services, such as the names of service providers, etc.

SIT Selection Information Table

The SIT is used only in "partial" (i.e. recorded) bitstreams. It carries a summary of the SI

information required to describe the streams in the partial bitstream.

TDMA Time Division Multiple Access

A digital wireless transmission technology TDMA is used by the digital system Global System for Mobile Communications (GSM) as a cellular phone technology to fit more cellular users in sequence on a single radio without interference from other callers. This form of technology is called multiplexing. A call is placed and sounds are digitized and then the information is broken into data packets which given a unique time assignment.

TDT Time and Date Table

Provides current UTC time

TNC Technically Non-Conformant

Does not comply with standards; Little or no subscriber impact

TOA Transport Stream Off-Air

Sync Loss; Loss of all programs in the Multiplex

TOT Timing Offset Table

Contains the UTC time and local time office

TR101 290 Test Standards that ensure viewer experience

TS Transport Stream

Provides mechanism to transmit multiple video PES; multiple audio PES, Scheduling Information, closed caption/subtitles, private data; and carousal multiplexed data onto a single data stream

VCT Virtual Channel Table

Uses all channels in the Transport Stream. Includes channel name, stream components and navigation identifiers. Carries the source ID for each program which is then used by the EIT to create the EPG