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Glossary for Interactive TV

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Advanced Application Platform specified by ATSC. ACAP is based on the GEM and DASE standards and includes some additional functionality from OCAP.

Ad Avails
Advertising spots available to a cable operator to insert local advertising on a cable network.

Application Information Table. Provides information about the activation state of bound OCAP applications.

ATSC Link-layer Protocol, as defined in A/330. ALP provides link layer signaling consisting of a header, links, and payloads. The link layer protocol isolates various transport types from the Physical (Transmission) Layer. ALP allows broadcasters to perform IP and TS packet encapsulation, segmentation and reassembly, concatenation, and header compression within this layer. The Link Mapping Table (LMT) is included in the ALP layer. The LMT provides a list of multicasts carried in a PLP. The LMT also provides additional information for processing the ALP packets carrying the multicasts in the link layer.

Amplitude Modulation
A process of transmitting radio frequency signals by varying the amplitude. This process is used for radio, television and fax.

American National Standards Institute - a standards body of the United States.

Application Protocol Data Unit. A common structure to send application data between CableCARD and the Host.

Application Programming Interface.

Association of Radio Industries and Businesses. Japanese iTV middleware standard.

ATCaster is an ATSC 3.0 broadcast stream generator written by S&T and sold by UniSoft. ATCaster is offered either individually or as part of UniSoft's ATSC 3.0 delivery system.

Automatic Testing Environment. This is a server and software architecture used by CableLabs and other organisations for the delivery of conformance tests to receivers under test ("RUTs").

Advanced Television Systems Committee formed to establish a set of technical standards for broadcasting in High Definition (HDTV). UniSoft is currently a member of ATSC.

The ATSC Signature File Generator. A UniSoft provided product that will sign ATSC 3.0 signaling and applications as required by the A/360 specification. ATSC SFG is integrated with S&T's ATCaster broadcast stream generator.


Bandwidth: The data rate of a digital signal which is commonly stated in units of bits-per-second (bps).

Bound Application
Applications (OCAP and MHP usually) which are associated with a particular TV channel (service). When the viewer changes channel, the application bound to the previous channel is terminated.

Broadcast Tunnel
A stream of packets sent from a CMTS to a cable modem embedded in a set-top-box or receiver.


Removable security card for digital cable terminals, as defined by the OpenCable project.

Certification Data Table. The A/360 specification defines a new LLS table that carries X.509 Certificates and OCSP responses that are used to verify signed ATSC 3.0 Signaling Messages. The Certification Data LLS table has the LLS_table_id 0x06.

Certificate File
A digitally signed file containing the public key used in digital signature verification and details of the owner and issuer of that public key.

Certificate files have a variety of filename extensions, including .crt, .cer, .pem, or .der. These extensions generally map to two major encoding schemes for X.509 certificates and keys: PEM (Base64 ASCII), and DER (binary).

Campaign Information Package Interface. The CIP is a component of SaFI which is used to inform all MSO systems that have a direct role in the preparation, delivery, execution, or reporting of the interactive campaign elements.

Cryptographic Message Syntax. This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content.

The Ryarc Campaign Manager CM Player (CMPlayer) is “business end” of the Campaign Manager system. The CMPlayer is responsible for playing back media and managing playlists, media downloads as well as monitoring system health.

Cable Modem Termination System. A router which interfaces between Ethernet networks and RF network connections to cable modems.

OpenCable Content Definition Format. This CableLabs' specification defines a standard format in which ETV and OCAP applications may be distributed amongst application authors, application playout systems and a variety of content delivery systems.
CoDF files are written in XML and describe the various components that may comprise a simple to complex application. Components can be application resources, data, or signaling. The CoDF syntax includes instructions for how to integrate an application, data and signals into a stream, with or without a video/audio component.

Common Download
A protocol for OpenCable-certified hosts for the purpose of updating any of the firmware objects used in the host device.

Code Verification Certificate. This is a X509 certificate issued by a Cablelabs' approved Certificate Authority (typically the CableLabs CVC CA) and used for signature of code images or CVTs.

Code Version Table. A message used to indicate the availability of a code image download when signaled to the eSTB component of a Host device.


Digital Access Controller. Cable headend control system from Motorola used by many of the US MSOs and cable operators.

Downstream Channel Descriptor. A DSG address table used within the DOCSIS MAC Management Message to manage the DSG Tunnel. DCDs sent out by a CMTS can be detected by an OCAP receiver and provide the receiver with sufficient information to receive data from the DSG tunnel. XAITs can be transmitted down DSG broadcast tunnels.

Digital Consumer Terminal. Digtial cable set-top-boxes manfactured by Motorola and used by many US cable companies. Some DCT models, such as the DCT2000, can support both analog and digital signals. Digital transmission can be either QAM 64 or QAM 256 modulated.

A data structure used in MPEG encoding which consists of tag, length and value (TLV) fields. Private descriptors may also be defined where the data portion (value) of these descriptors is privately defined.

A message digest is a one way function that generates a statistically unique sample for a set of input data.

DigiCipher II
DigiCipher II, DigiCipher 2, or DCII, is a proprietary standard format of digital signal transmission and encryption with MPEG-2 video compression. The DCII standard was originally developed in 1997 by General Instrument, which is now the Home and Network Mobility division of Motorola. The use of DCII is most prevalent in North American digital cable television set top boxes.

Designated Market Area. With respects to TV advertising, DMAs provide a way of designating particular geographic markets and are often ranked by the size of population.

Digital Network Control System, a product of Cisco (formerly Scientific-Atlanta, Inc.). The Digital Broadband Delivery System (DBDS) receives analog and digital services from a variety of sources including satelitte and securely transports the services to the subscribers home. Services supported by the DBDS are controlled by the DNCS.

DOCSIS Set-Top Gateway.

DSG Address Table
The collection of DSG Rules and DSG Classifiers contained within the DCD message.

Digital Storage Media Command and Control. A format for transmission of data and control information in an MPEG-2 Private Section, defined by Part 6 of the ISO/IEC 13818 MPEG-2 standard. Applications of which include data and object carousels. These data structures are used to transmit EBIF and OCAP applications respectively.

Digital Transport Adapter, a unit which converts digital standard definition TV signals to analogue NTSC allowing cable operators to transition to all-digital broadcasting - the DTA provides a solution for the analogue subscribers. Transistion to all digital allows the operator to reallocate analogue bandwidth for the deployment of many High Definition digital channels.

Digital Video Broadcasting program within the European Broadcasting Union (EBU). DVB specified the MHP middleware standard.


Emergency Alert Signaling method for cable TV. This is a standard which defines an Emergency Alert signaling method for use by cable TV systems to signal emergencies to digital set-top-boxes.

ETV Binary Interchange Format. The binary format used to encode ETV applications.

ETV Integrated Signaling Stream - an MPEG elementary stream which carries media timeline messages, stream events and EISS tables for an ETV application.

Enhanced Television, a specification by CableLabs which allows deployment of interactive content on "thin-clients" such as the Motorola DCT 2000 (with over 15M platforms deployed) and Scientific Atlanta Explorer 2000 as well as OpenCable (OCAP) host devices.

The European Telecommunications Standards Institute, a recognized standards body located in Southern France.


File Delivery over Unidirectional Transport. Used for file delivery of ATSC NRT content. FLUTE is a protocol for delivery of arbitrary types of files over a unidirectional IP link. It uses the IETF ALC (Asynchronous Layered Coding) protocol, which in turn uses the IETF LCT (Layered Coding Transport) protocol.

Forward Channel
The direction of radio frequency (RF) signal flow away from the headend toward the end user; equivalent to downstream.


Globally Executable MHP. A terminal specification based on MHP that enables applications to interoperate across OCAP, MHP and other GEM based platforms.


The control centre of a cable television system, where incoming signals are amplified, converted, processed, and combined into a common cable, along with any origination cable-casting, for transmission to the home.
HTML Entry pages Location Description. A fragment of ATSC 3.0 Service Layer Signaling which provides application-related metadata that enables the loading and unloading of an ATSC 3.0 interactive application.

Host Device
Set-top-box or receiver containing and executing the OpenCable Application Platform implementation. It is also host to the CableCARD device.


Interactive Application Fulfillment Summary Interface is a component of the CableLabs' SaFI specification. The IAF provides a means for messaging generated by an interactive application to be exposed to an external entity. Whilst individual messages may flow over this interface, more typically a summary of messages is transmitted, e.g., the aggregated results of a voting application.

Interactive Application Messaging (IAM) is a component of the CableLabs' SaFI specifications. IAM defines the format and content of of messages generated by interactive (EBIF) applications on a cable receiver and transported to a network component within an MSO system.

Internet Media Subtitles and Captions Version 1. How subtitles are carried in ATSC 3.0 as per the ATSC standard "Captions and Subtitles (A/343)".

Interactive TV usually means the viewer using the remote control to "interact" with the TV to change the available video, audio and any graphics in some way. These changes are typically made by an interactive software application running in the set-top-box or TV.


Java Virtual Machine.


Key Pair
A public and private key pair. Information is encrypted using a private key and others can use the corresponding public key to decrypt. If decryption is successful, you have a high degree of confidence the transmitted information originated from the registered holder of the private key.

Kit Files
With respects to SoftOC, Kit Files consist of transport packets and DSM-CC modules plus an XML kit-control file. The control file describes how to multiplex these parts at the section level in order to achieve user defined MPEG /DVB/DSM-CC/OCAP table repetition rates.


Layer Division Multiplexing. As defined in the physical layer specification, A/322, LDM is a constellation superposition technology that combines multiple PLPs at different power levels, often with different modulation and channel coding schemes, prior to transmission in one RF channel. Currently only two-layer LDM is used, a Core (or upper layer) and an Enhanced (or lower layer). Generally use of LDM allows broadcasters to squeeze some additional bandwidth into their 6MHz channel.

Line 2238 Club
A delightful piece of UNIX folklore. A notion created by John Loins in Chapter 8 of his publication in 1976 "A Commentary On The UNIX Operating System". The commentary included the entire UNIX Version 6 source code and line 2238 is equivalent to line 325 of ken/slp.c; a comment in the C code which reads "You are not expected to understand this.". Those that understand how V6 process swapping works fully on a PDP 11 architecture are members of this club.

Link-local Addresses
A link-local address is a network address that is valid only for communications within a network segment (a single network link, or often: one broadcast domain) that a host is connected to. Usually, link-local addresses are not guaranteed to be unique beyond a single network segment. Routers therefore do not forward packets with link-local addresses.

Link-local addresses for IPv4 are defined in the address block In IPv6, they are assigned with the fe80::/64 prefix.

Multi-user operating system used by many OCAP receiver manufacturers to execute their OCAP middleware implementations.

ATSC 3.0 Low Level Signaling. Delivered via multicast to port 4937. The LLS carries a number of table types including the Service List Table (SLT), Rating Region Table (RRT), System Time Table (STT). Advanced Emergency Alert Table (AEAT) and the On Screen Message Notication (OSMN) table.

S&T's broadcast stream generator, ATCaster , will generate LLS for ATSC 3.0.

Link Mapping Table. ATSC 3.0 signaling, LMT provides a list of multicasts carried in a PLP. The LMT also provides additional information for processing the ALP packets carrying the multicasts in the link layer.


Multimedia Home Platform specification produced by DVB.

In the context of interactive TV, the software which runs on a TV receiver which is layer between the operating system and the applications. Most middleware which are open standards are based on Java.

Multiple Input Multiple Output. One of three ATSC 3.0 frame types (SISO, MISO, MIMO). MIMO improves system robustness via additional spatial diversity (two transmit, two receive antennas) which is often combined with polarization diversity (H-pol and V-pol).

Multiple Input Single Output. One of three frame types (SISO, MISO, MIMO). MISO is a pre-distortion technique that artificially de-correlates signals from multiple transmitters in a Single Frequency Network in order to minimize potential destructive interference.

Multicast Listener Discovery Protocol. MLD is used by IPv6 routers for discovering multicast listeners on a directly attached link, much like IGMP is used in IPv4. The protocol is embedded in ICMPv6 instead of using a separate protocol. MLDv1 is similar to IGMPv2 and MLDv2 similar to IGMPv3.

Man Machine Interface is another term for User Interface. With respect to OCAP, MMI specifies the protocol used over the CableCARD/host interface to enable the CableCARD device to display messages on the television display.

MMT – MPEG Media Transport, ISO/IEC 23008-1. This an alternative to ROUTE for transmission of ATSC 3.0 broadcast services over IP, where MMT protocol (MMTP) is used to deliver Media Processing Units (MPU).

With respects to TSBroadcaster systems, a model means a snapshot capture of a current TSBroadcaster configuration which is placed in a ZIP file. The model includes all applications which have been registered with TSBroadcaster, play-out schedules and configuration data. Models can be uploaded to, and download from, a running TSBroadcaster system.

Modulation is the process of conveying a message signal, for example a digital bit stream, inside another signal that can be physically transmitted. For cable a plant, modulation is often to QAM for transmission over RF. Modulation Mode in the context of the SCTE-65 service information standard relates to a field of the Longfrom Virtual Channel Table (LVCT) where the type of modulation used is defined.

Moving Picture Experts Group. A group which develops standards for digital, compressed moving pictures and associated audio. MPEG-2 is a video compression standard commonly used by cable television operators.

Multiple System Operator. A term for US cable companies that operate multiple cable systems. Time Warner Cable and Comcast are MSOs.

MHP Test Consortium.


N+1 Redundancy
A mechanism for failure recovery in computer architectures which consist of multiple server systems. An additional server, known as a "hot spare", is included which can act as a replacement if any one of N systems fail.

Network Address Translation. NAT is the process of modifying IP address information in IP packet headers whilst in transit across a traffic routing device.

The simplest type of NAT provides a one-to-one translation of IP addresses and is known as "basic NAT" or "one-to-one NAT". NAT is often used for IP address conservation. In this case it is common to hide an entire IP address space, usually consisting of private IP addresses, behind a single IP address (or in some cases a small group of IP addresses). To avoid ambiguity in the handling of returned packets a one-to-many NAT must alter higher level information such as TCP/UDP ports in outgoing communications and must maintain a translation table so that return packets can be correctly translated back. The terms NAPT (network address and port translation), PAT (port address translation), IP masquerading, NAT Overload and many-to-one NAT are used to describe this use case.

Native Application
Typically an application which is written for the operating system of a receiver (set-top-box) rather than the middleware standard that may also be running on the receiver. ETV User Agents are implemented as native applications.

Network Information Table. The NIT is a Service Information table carried in PID 0x1FFC and present in SCTE-65. The NIT has a table_ID of 0xC2. This table delivers sections of non-textual tables. The table types included in the NIT are the Carrier Definition Subtable (CDS) and the Modulation Mode Subtable (MMS).

Non-Real-Time. An ATSC standard defined in A/103 which refers to content that is delivered in advance of its use and stored in the receiving device. May refer to content that is delivered faster than real-time, such that buffering is required in the receiving device.

Network Text Table. The NTT is a SCTE-65 Service Information table carried in PID 0x1FFC. Each instance of NTT is associated with a language, as such the textual information may be provided multi-lingually. The NTT may include a Source Name Subtable (SNS).


Object Carousel
A format for the transmission of data and events to the terminal. These formats are defined in ISO/13818-6 standard. Their usage is defined in a profile contained in DVB-MHP Specification Annex B. Essentially these definitions provide a way of transmitting a Unix-like file system down a broadcast channel. TSBroadcaster is capable of generating object carousel.

OpenCable Application Platform, the US cable industry's middleware standard specified by CableLabs. Also known as "tru2way". OCAP is Java based.

OCAP Automatic Test Environment. This is the OCAP version of the ATE (see "ATE" above) which is used by CableLabs to deliver the OCAP conformance tests to receivers under test.

Host server system for the OCAP Automatic Test Environment (ATE).

OCAP Socks
Fabulously stylish socks made available by UniSoft at a variety of tradeshows at the height of the popularity of OCAP. These classic giveaways were followed by many fantastic items including OCAP/EBIF shot glasses, beer openers and more recently ATSC 3.0 socks, rubber ducks and spatulas.

OCSP is Online Certificate Status Protocol which allows us to check the validity status of a certificate in real-time. It is an alternative to CRL or Certificate Revocation Lists.

OCSP Stapling
OCSP Stapling, and speicifically in the context of ATSC 3.0, is the process of including a digitally-signed and time-stamped version of an OCSP response in the LLS. This stapled OCSP response is then refreshed at predefined intervals set by the CA. This aproach is essential for 3.0 receivers that do not have an internet connection. In a web server context, OCSP Stabling improves performance of web browers which do not need to access an OCSP Responder each time the user visits an encrypted page.

A project established by CableLabs, to standardize a cable network interface and to build a retail market for digital cable terminals.

Out-of-Band (OOB)
An out-of-band is a channel which is the combination of the forward and reverse OOB channels. The OOB channel provides an IP-based communication channel between a cable network and the set-top-box.

Out-Of-Band-Forward-Data-Channel (OOB-FDC).
The portion of the cable RF range that is used to deliver system or service information to a receiver. Its frequency range is generally 70-130 Mz.

Out-Of-Band-Reverse-Data-Channel (OOB-RDC).
The portion of the cable RF range that is used to deliver data from the home receiver to the headend. Its frequency range is 5-40 Mz.


Profile, Demongraphics and Interest. An ATSC 2.0 term for data about a specific TV viewer.

Packet Identifier. A unique integer value used to identify elementary streams of a program in an MPEG-2 transport stream.

This standard describes a general syntax for data that may have cryptography applied to it, such as digital signatures and digital envelopes. The standard allows recursion, so that, one envelope can be nested inside another, or one party can sign some previously enveloped digital data.

A file format commonly used to directly store a private key along with its X.509 certificate. A PKCS #12 file, and subparts thereof, may optionally be encrypted and signed. These files can be created, parsed and read out with the OCAPSFG or OpenSSL pkcs12 commands.

Physical Layer Pipe – a portion of an ATSC 3.0 RF channel which has certain modulation and coding parameters. One 6MHz channel may contain several different PLPs.

Program Map Table. An MPEG-2 table which provides data and location on all TV services in the transport stream.

Private Section
A type of MPEG Section. Specifically a private_section must be used when private data is sent in Transport Stream packets with a PID value designated as a Program Map Table PID referenced by the Program Association Table.


Quadrature Amplitude Modulation. A type of modulation typically used by US cable plants for in-band distribution. Most common varieties of QAM used are 64-QAM and 256-QAM.

Quadature Phase-Shift Keying - A digital modulation technique which changes the phase of the reference signal or carrier wave using four phases. US cable headends often use QPSK modulation for the out-of-band channel.


Root Certificate Authority.

Return Channel
A data path that goes from the subscriber to the cable headend. Also known as Upstream, Reverse Path or Return Path.

RF - Radio Frequency
Analog electrical signals sent over the cable. Television signals are modulated onto RF signals and are then demodulated by the television's tuner or set-top-box.

Radio Frequency Radiation. A type of low-energy radiation, emitted from a variety of devices including TV transmitters. RFR is a type of non-ionizing electromagnetic radiation. Although there have been health concerns, most types of RZR have not been found to cause harmful health effects. RZR is regulated by the FCC.

Real-Time Object Delivery over Unidirectional Transport. A protocol used by ATSC 3.0 to deliver service signaling and MPEG DASH segments. ROUTE is a derivative of the FLUTE protocol mentioned above.

RSA - Rivest, Shamir and Adleman
Commonly used to describe a key which is asymmetric. Asymmetric keys have separate private and public components based on prime numbers such that data encrypted using one component can only be decrypted using the other component.

RSSi - Received Signal Strength indicator
RSSi is a measurement of the power present in a received RF signal.

Receiver, or terminal, Under Test, a term used often with respect to the MHP and/or OCAP ATE.


Service-based Transport Session Instance Description. An ATSC 3.0 SLS XML fragment which provides the overall session description information for transport session(s) which carry the content components of an ATSC 3.0 service.

Stewardship and Fulfillment Interfaces. A collection of interfaces defined by CableLabs to support advanced services on multiple cable systems.

The Society of Cable Television Engineers, a non-profit professional association responsible for development of standards, their certification and provision of related information.

SCTE specification, set out in multipled parts, which describes a framework for dynamically selecting and splicing advertisements. Such ads, may vary in length, and subject matter. The splice may be into linear, stored, or switched video content. Essentially SCTE-130 enables personalized and targeted advertising.

SCTE standard which defines an Emergency Alert signaling method for use by cable TV systems. SCTE-18 defines a cable_emergency_alert() message in the form of an MPEG-2 private_section(). MPEG-2 table_ID for this message is 0xD8.

SCTE standard which supports the splicing of MPEG-2 streams for the purpose of Digital Program Insertion. This includes insertion of advertisements and other content types. SCTE-35 defines how ad insertion control messages (cue messages) may be inserted and used in TV broadcast systems.

Standard for Service Information delivered Out-of-Band for digital cable television. OCAP set-top-boxes may receive channel maps delivered in SCTE-65 format if delivered via DSG broadcast tunnels type 1.

A section is a syntactic structure that is be used for mapping all MPEG-2 (ISO/IEC 13818-1) defined PSI tables into Transport Stream packets.

Service Information. Information that describes the TV services available on the network. OCAP service information is defined by the SCTE 65 standard.

Signature File
A file containing a unique code generated by applying a private key against a known, reproducible, set of data. The converse operation of applying the corresponding public key against the unique code will reconstruct the original data.

ATSC 3.0 Service Layer Signaling. Signaling information which provides sufficient details for the discover and acquistion of ATSC 3.0 services. Often SLS data is multicast to the address 239.255.M.N where M is the major channel number and N is the minor channel number.

ATSC 3.0 Service List Table, provides the information for an ATSC 3.0 receiver to build a basic service list. The SLT is carried in the LLS.

Service Measurement Summary Interface, a component of SaFI which specifies a data model and transmission protocol for delivery of service measurement summary information from an MSO system to an external entity.

Signed Multi Table which contains a list of all the LLS tables (with the exception of the CDT), their version, length (in bytes), security signature (as provided for in ATSC A/360) and signature length.

The Service Map Table. An MPEG-2 table which contains service-level attributes for ATSC NRT Services carried in the fixed-broadcast Transport Stream.

SNR or S/R
Signal-to-Noise Ratio, is a measure that compares the level of a desired RF signal to the level of background noise. Digital TV tuners will generally process signals from about -50 dBm (strong) to about -80 dBm (weak).

DSM-CC object carousel generator and transport stream encoder used by the MHP and OCAP ATEs.

Stream Event
A type of Trigger that conveys application defined messages to an application (typically an EBIF or OCAP application).

Short-form Virtual Channel Table. The S-VCT is a Service Information table defined in SCTE-65 with a table_ID of 0xC4. There are three map types currently defined for S-VCT: the Virtual Channel Map (VCM), the Defined Channels Map (DCM), and the Inverse Channel Map (ICM).


Broadcast service which uses several otherwise unused scanning lines (vertical blanking intervals) between frames of TV pictures to transmit information to receiving TVs. This service has been very popular in the United Kingdom for many years.

Test Harness
A test harness provides a framework for building, execution and reporting of tests results.

Transport Stream
Specifically an MPEG transport stream, is a standard format for transmission and storage of digital audio, video and associated data. The detailed structure of a Transport Stream is specified in MPEG-2 Part 1. The transport stream structure specifies a container format encapsulating packetized elementary streams, with error correction and stream synchronization features for maintaining transmission integrity when the signal is degraded.

Transport streams differ from Program Streams in several important ways: program streams are designed for reasonably reliable media, such as DVDs, while transport streams are designed for less reliable transmission, namely terrestrial, satellite or cable broadcast. In addition, a transport stream may carry multiple programs.

A broadcast message that provides a synchronization mechanism to an interactive TV application (such as an EBIF application). Triggers may be embedded in the associated video program, or delivered via another means such as the out-of-band. Triggers may also be used for the delivery of unsolicited data to an application. Triggers may include application signals and stream events.

is the interactive TV standard for use cable systems. It replaces the term "OpenCable Platform" and is CableLabs' brand for the OCAP middleware standard.

An encoding solution and DSM-CC carousel generator which handles automatic and scheduled playout of OCAP, ETV and MHP applications.

A legacy version of TSBroadcaster with QAM output, suitable for lab testing.

Multiplexor and play-out software used by the OCAP ATE to broadcast OCAP test cases through ASI output.

An MPEG-2 transport stream player used by TSBroadcaster for output via ASI or Gigabit Ethernet.

Timed Text Markup Language, is a W3C-developed closed-captioning data-delivery standard which is used by ATSC 3.0.


Unbound Application
An OCAP application which is not bound to a particular service. It is present across all of the TV channels. OCAP EPGs and the Monitor Applications are unbound.

Unbound Declarative Object
An ATSC 2.0 Declarative Object that is not bound to a particular terrestrial TV service.

User Service Bundle Description. Another component of ATSC 3.0 signaling, essentially a XML-based SLS fragment which provides entry point information for the description and discovery of an ATSC 3.0 service.

User Agent
Usually used in the context of ETV, a User Agent is native application which interprets EBIF binary code and renders images on the TV screen appropriately.


Video on Demand. A feature which allows TV viewers select (usually from the program guide) a movie or program to be played almost immediately. Usually VOD services are provided by VOD servers located in the cable company's headend.

Viewer Category
Viewer Category is a classification which can be used to direct advertisments towards an audience with certain traits, based on the product or person the advertiser is promoting. Such selection criteria can be demographic or psychographicly focused on the consumer values, personality, attitude, opinion, lifestyle and interest. This focus can also entail behavioral variables, such as browser history, purchase history and other recent online activities.


W3C Consortium - An organization formed to develop common protocols to ensure interoperability and promote the World Wide Web.


eXtended Applicaton Information Table. An enhanced version of the AIT used to signal unbound OCAP applications.

X.509 is an ITU-T standard for a public key infrastructure (PKI).

An application validator for OCAP, ETV-EBIF, MHP, ACAP and JSR-242 application conformance testing.

XLink XML Linking Language. In ATSC 3.0, XLinks can be used to provide a mechanism allowing the Broadcaster Application to replace a DASH Period marked with an XLink attribute with a Period fragment referencing alternate content, allowing Ad (or content) replacement. Usually the encoder/packager converts incoming SCTE-35 (in a transport stream) or SCTE-104 (in baseband) to multi-period DASH with XLinks appropriately placed in the DASH MPD.


YouTube is a video-sharing website on which users can upload, share, and view videos.


Zapper Box
Slang expression for very simple and cheap set-top-boxes that contain minimum functionality.

A Zone is a local area or subset of a DMA.