Interactive TV

Consumers are increasingly staying connected to their content world through fixed and mobile devices. This connectivity requires a level of interactivity that is far-reaching as well as easy-to-use. This month, we'll look at some of the technical initiatives under way to bring interactivity to the broadcast television experience.

Interactive TV has seen few applications to date that tie together the consumption of broadcast with true user involvement. While Internet TVs have been available for several years, the apps available on these products do not truly integrate the broadcast and connected worlds; they are essentially separate means of consuming content on a common display. Interactivity that can provide new broadcast features to users, while at the same time providing new business opportunities to broadcasters, is still an untested business model. However, the potential is there.

These new features include video-on-demand, click-through information and advertisements, ad verification, interactive polling, interactive overlays, chat sessions, and E-commerce. But, supporting interactivity broadly and efficiently requires standardized technical solutions. The good news is that some elements are already available, and additional work is under way.

New ATSC work

In the United States, the ATSC has several interactive technologies defined, and more in development. ATSC A/96, Interaction Channel Protocols, describes interactivity protocols, based on IETF and W3C standards, enabling interactive TV applications using a two-way channel in combination with an OTA broadcast channel. (See Figure 1 on page 22.)Published in 2004, A/96 defines an interactive applications framework, using a five-layer reference model with a data-link layer, a network layer, a transport layer and an application protocol layer. The network layer-related protocols are based on a TCP/IP and UDP. At the application level, A/96 uses standard HTTP 1.1 protocols.

ATSC A/101, the Advanced Common Application Platform (ACAP), revised in 2009, was developed so interactive application developers would have means to ensure interoperability between applications and compatibility with different devices. ACAP was developed as a harmonization effort between the ATSC DTV Application Software Environment (DASE) and CableLabs' Open Cable Application Platform specifications.

The A/96 and A/101 standards have not seen widespread implementation, however, pre-dating the recent swarm of Internet TVs and now potentially being overtaken by a new suite of standards. Under the umbrella of ATSC 2.0 will be a complete suite of new services for fixed DTV receivers, including Non-realtime (NRT) and Triggered Downloadable (or Declarative) Objects (TDOs).

NRT provides a framework for pushing content to fixed and mobile broadcast receiving devices in advance of consumption. Together with TDOs, services such as personalized content, targeted or telescoping content/ads, Internet content, audience measurement and second-screen content can be supported. A TDO is a Declarative Object (a list), associated with a virtual channel, that carries out a programmed routine when activated; a Declarative Object can support an interactive application by using HTML, JavaScript, CSS, XML and multimedia files. ATSC 2.0 will use transport and signaling based on NRT, and will incorporate elements in common with Hybrid Broadband Broadcast TV (HbbTV) and the Open IPTV Forum (OIPF).

European development

HbbTV is a pan-European specification, based on HTML and web technologies, targeted to hybrid terminals (e.g., connected TVs) that receive an over-the-air transmission and can be connected to the Internet via a broadband interface. HbbTV is based on several standardized technologies developed by CEA, DVB, OIPF and W3C.

CEA-2014 is the web-based Protocol and Framework for Remote User Interface on UPnP Networks and the Internet (Web4CE), also known as CE-HTML. The standard provides a structured way of accessing a user interface and related content over an IP network, in a manner that is optimized for CE devices. Used in HbbTV, CEA-2014 is a subset of W3C specifications and image formats, using XHTML and JavaScript APIs in an on-demand media environment. OIPF, which defines a Declarative Application Environment, incorporates aspects of CE-HTML, as well as JavaScript APIs for the TV environment. With these, applications such as channel tuning, advanced EPG, PVR functions and control of in-home networked devices are possible.

DVB has numerous elements that support interactivity, many of which are defined in ETSI TS 102809, “Signaling and carriage of interactive applications and services in Hybrid Broadcast Broadband environments.” These applications, in turn, rely on MHP, the Multimedia Home Platform.

One of the many useful elements of MHP is Application Signaling. It defines a service information table — the Application Information Table (AIT). Sent in the main signal transport stream, the AIT lists all available applications to the receiver. It also contains in ormation the receiver needs to run each application. Applications are transported using Digital Storage Media Command and Control (DSM-CC) object carousels. Part of MPEG-2, DSM-CC defines a commands set that can provide VCR-like functions over a client-server connection. DSM-CC further uses “stream events,” markers embedded in a transport stream via MPEG-2 private sections. Each marker has an identifier and time reference. Similar to some aspects of TDOs, these stream events can thus synchronize elements of OTA broadcast and Internet-provided content.

HbbTV supports XHTML (Extensible HyperText Markup Language), a W3C standard, which is a better-defined version of HTML. XHTML is almost identical to HTML 4.01, and is therefore supported by major browsers. HbbTV also incorporates CSS 2.1, CSS-TV, DOM-2 (including XML Document support) and ECMAScript. Cascaded Style Sheets (CSS) define how web pages are displayed on devices, and the CSS-TV Profile further defines color specifications tailored to needs and constraints of TV displays. DOM-2 specifies an interface that works across platforms and languages, and allows programs and scripts to dynamically access and update the content and structure of documents. ECMAScript (originally, the European Computer Manufacturers Association) is a scripting language, based on JavaScript (from Netscape) and Jscript (from Microsoft), used for performing computations and manipulating objects within a processing device. It was originally developed to allow web applications to access processing power of the host PC.

HTML5 is a new specification under development to replace existing HTML used by web browsers. It includes functions for embedding and controlling video and audio, graphics and interactive content, and supports local offline storage of session data. HTML5 has been shown as a component of an HbbTV browser.

New businesses

While many of these concepts apply most directly to content authoring and control, they give an idea of what new elements will appear in interactive streams, and how different devices can be made to react consistently and universally. Digital transmission, while offering the potential for extensive interactivity, has so far only scratched the surface, due to the rapid change of content consumption business models. The tools described here will facilitate exploration and development of interactive TV for a new realm of products.


TV shipments down in 2011
NPD DisplaySearch said worldwide TV shipments fell for the first time since 2004, the first year it began tracking shipping data.

Technology Q4'11 units Q/Q growth Y/Y growth LCD TV 64,237 24% 1% PDP TV 5195 26% -8% OLED TV 0.1 470% -73% CRT TV 4772 -25% -43% RPTV 32 46% -51% Total 74,236 19% -4%

Source: “Quarterly Global TV Shipment and Forecast Report”

Aldo Cugnini is a consultant in the digital television industry.

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