Overview about HbbTV architecture
What is HbbTV® – and what is it not?
Hybrid broadcast broadband TV (HbbTV) is a global initiative dedicated to providing open standards for the delivery of advanced interactive TV services through broadcast and broadband networks for connected TV sets and set-top boxes.
|HbbTV ® is||HbbTV ® is NOT|
|Business neutral technology platform Applicable to terrestrial, cable and satellite broadcast and broadband networksAllows to combine broadcast and broadband service elementsMaintains integrity of broadcast services, including all related elementsIntegrates an application managementBroadband link recommended, broadcast only mode possibleSpecifies only device (terminal) behavior||Completely specified ecosystem, e.g. including implementation rulesSolely applicable to over-the-air (OTA)broadcast or broadcast in general|
The key building blocks
Important components provided by HTML5 (W3C) include:
- The HTML markup language itself.
- The <video> element for presenting broadband delivered video in an HTML page.
Important components provided by the Open IPTV (OIPF DAE) specification include:
(e.g. broadcast video presentation, channel change).
- Definition of embedding linear audio and video (A/V) content in an application.
- Integration with content protection/DRM technologies
DVB (ETSI TS 102 809) provides the following components:
- Application signalling.
- Application referencing via HTTP
- Transport of applications via broadcast.
The audio and video formats are defined in the OIPF Media Formats specification.
A hybrid terminal has the capability to be connected to two networks in parallel. On the one side it can be connected to a broadcast DVB network (e.g. DVB-T, DVB-S or DVB-C). Via this broadcast connection the hybrid terminal can receive standard broadcast A/V (i.e. linear A/V content), non-realtime A/V content, application data and application signalling information. Even if the terminal is not connected to broadband, its connection to the broadcast network allows it to receive broadcast related applications. In addition, signalling of stream events to an application is possible via the broadcast network.
In addition the hybrid terminal can be connected to the Internet via a broadband interface. This allows bi-directional communication with the application provider. Over this interface the terminal can receive application data and non linear A/V content (e.g. A/V content streaming on demand). The hybrid terminal may also support non-real time download of A/V content over this interface. The broadband interface may also connect to Companion Screen Devices or other HbbTV® terminals on the same local network as the hybrid terminal.
Via the Broadcast Interface the terminal receives AIT data, linear A/V content, application data and stream events. The last two data streams are transferred by using a DSM-CC object carousel. Therefore a DSM-CC Client is needed to recover the data from the object carousel and provide them to the Runtime Environment.
The Runtime Environment can be seen as a very abstract component where the interactive application is presented and executed. The Browser, an Application Manager and the Companion Screen Interface form this Runtime Environment. The Application Manager evaluates the AIT to control the lifecycle for an interactive application. The Browser is responsible for presenting and executing an interactive application.
Linear A/V content is processed in the same way as on a standard non-hybrid DVB terminal. This is included in the functional component named Broadcast Processing which includes all DVB functionalities provided on a common non-hybrid DVB terminal. Additionally some information and functions from the Broadcast Processing component can be accessed by the Runtime Environment (e.g. channel list information, EIT p/f, functions for tuning). These are included in the “Other Data” in the figure above. Moreover an application can scale and embed linear A/V content in the user interface provided by an application. The Media Player provides these functionalities.
Via the Broadband Interface the hybrid terminal has a connection to the Internet. This connection provides a second way to request application data from the servers of an application provider. Also this connection is used to receive A/V content (e.g. for Content on Demand applications). The component Internet Protocol Processing comprises all the functionalities provided by the terminal to handle data coming from the Internet. Through this component application data is provided to the Runtime Environment. A/V content is forwarded to the Media Player which in turn can be controlled by the Runtime Environment and hence can be embedded into the user interface provided by an application. In combination with the Media Player, the Synchronization Manager can synchronize content delivered to the hybrid terminal via the Broadband Interface and content delivered to the hybrid terminal via either the Broadband Interface or the Broadcast Interface.
The Companion Screen Interface enables the hybrid terminal to discover Companion Screen Devices and other hybrid terminals and to be discovered by Companion Screen Devices. Through it, interactive applications running in the Browser can request an application be installed or started on a Companion Screen Device and an application running on a Companion Screen Device can request the Browser to start an interactive application. It provides a WebSocket server to enable an interactive application in the hybrid terminal and an interactive application on either a Companion Screen Device or a different hybrid terminal to communicate. In combination, the Companion Screen Interface and the Media Player together enable synchronization of content delivered to the hybrid terminal via either interface with content delivered to a Companion Screen Device or another hybrid terminal.
Via the CI Plus interface, the hybrid terminal requests application data from the Auxiliary File System offered by the CICAM.
Broadcast-independent and broadcast-related applications
There are 2 types of HbbTV applications:
- A Broadcast-independent application (i.e. not associated with any broadcast service). This type of application is downloaded via broadband and accesses all of its associated data via broadband.
- A Broadcast-related application (i.e. associated with one or more broadcast services or one or more broadcast events within a service) that may be launched automatically (“autostart”) or explicitly upon user request. This type of application may be downloaded via broadband or broadcast and may access its data via either method.
In the above example Quiz and TV guide are broadcast-related HbbTV applications (launched from broadcast services using the red RC button), while Portal, VoD and Weather are broadcast-independent HbbTV applications. Portal application is launched by the terminal using a dedicated RC button, while VoD application and Weather application are launched from Portal application.