# TV Data Glossary — EPG Service

> EPG, metadata, and content-delivery terms. Source: https://epgservice.tv/en/glossary

## Ad markers

Ad markers denote the start and end of ad and promo breaks on air. They are needed for ad-skip in catch-up, analytics, and dynamic ad insertion (DAI).

## Catch-up TV

Catch-up TV lets viewers watch an already-aired program on demand within a set window (typically 3–14 days). Catch-up quality depends on precise program start/end times and correct episode identification.

## Content ID

A Content ID is a unique identifier for a piece of content (film, series, episode, person) that is consistent across all platforms and sources. It links linear TV to VOD, removes duplicates in catch-up, and powers cross-platform recommendations. Comparable to a Gracenote ID.

## Content metadata

Content metadata is structured data about a film, series, or show: title, genres, cast, ratings, age restrictions, descriptions, posters. The EPG Service database holds 114 attributes across 15 groups.

## DAI (Dynamic Ad Insertion)

DAI (Dynamic Ad Insertion) dynamically inserts ads into the video stream for a specific viewer. It relies on ad-break markers and broadcast context.

## EPG (Electronic Program Guide)

EPG (Electronic Program Guide) is the electronic TV schedule: an interactive guide on a TV, set-top box, or app screen. It shows what is on now and next across channels, with descriptions, times, and genres. In IPTV/OTT, EPG data is delivered via XMLTV or a REST API.

## Episode ID

An Episode ID identifies a specific episode or installment with season and episode numbers. It enables correct catch-up (a rerun keeps the same ID, no duplicates), "Episode 5 of 12" navigation, and accurate recommendations even when the broadcaster did not provide numbering.

## Event Time

Event Time is the actual start and end time of a program on air, as opposed to the planned schedule. EPG Service records it with ±3 second accuracy — the basis for correct catch-up from the first frame and ad verification.

## Fact EPG

Fact EPG is the schedule of what actually aired, not what was planned. It accounts for delays and grid changes. It is needed for objective analytics, ad verification, and accurate catch-up.

## FAST channels

FAST (Free Ad-Supported Streaming TV) are free linear channels on streaming platforms monetized through advertising. They require quality EPG and metadata for navigation and ad targeting (DAI).

## IPTV

IPTV (Internet Protocol Television) delivers television over an operator’s IP network. The player or set-top box receives a channel playlist and a separate EPG (usually XMLTV), matching them by tvg-id.

## Middleware

Middleware is an operator’s software platform between the delivery network and the app on the subscriber’s device. It handles the UI, EPG, and subscription management; EPG data is supplied in middleware-compatible formats.

## OTT

OTT (Over-the-Top) delivers video over the open internet, without the operator’s own network. It includes streaming services and online cinemas, and often combines linear channels, VOD, and FAST.

## Timeshift

Timeshift is time-shifted viewing: pausing live TV, rewinding, and watching an in-progress program from its start. Like catch-up, it relies on precise broadcast timing.

## TV guide (telegid)

A TV guide (telegid) is the same as EPG: an electronic guide to the TV schedule on a device screen. The terms "telegid", "electronic TV guide", and EPG are used interchangeably.

## TV-VOD mapping

TV-VOD mapping matches linear TV content with VOD catalog entries via shared Content IDs. It lets recommendations work cross-platform so viewers do not see a boundary between live TV and the catalog.

## VOD (Video on Demand)

VOD (Video on Demand) is a library of content available to watch anytime, unlike linear scheduled broadcasting. Linking VOD to linear TV via Content IDs creates a unified content space.

## XMLTV

XMLTV is an open format for storing a TV schedule as an XML file. It describes channels (the channel tag) and programs (the programme tag with start/stop attributes). It is the de-facto standard for EPG in IPTV players and set-top boxes. Time is written as YYYYMMDDHHMMSS ±HHMM.