Here’s a look at the technologies behind content distribution over the Internet.
Content distribution over the Internet is not a new technology. However, various forms of content delivery to PCs and Internet-connected TVs, using the Internet or Internet mechanisms, have emerged and have created a confusing landscape. At the same time, standards organizations such as the ATSC are investigating schemes to interoperate new consumer devices with terrestrial broadcasting. This month, we'll look at the technologies behind these services, and we'll look to the future as to where these are headed.
The emerging alternate delivery mechanisms can be classified into different categories, depending on the different delivery paths and business models. Online video is perhaps the simplest mechanism, whereby content providers such as Hulu and Netflix serve up streaming or downloaded video on demand from Internet websites. Video content is prestored on servers and delivered to consumer devices as streamed files; the experience can be PC- or STB-based. The content is sent over a TCP-IP connection to the user, much the same way as web pages are sent to an Internet browser.
When displaying exclusively on a PC, any of various streaming video codecs is typically used, such as Adobe Flash or Windows Media Video. Playback is also possible on other Internet-connected devices, such as Blu-ray-linked TVs, handheld devices, gaming consoles, and set-top boxes, as shown in Figure 1. An interesting dilemma that online video has caused is that of over-the-top (OTT) content, such as when a cable-TV operator also provides Internet access; viewers can then access video through the Internet connection, with that content essentially competing with the cable operator's own video service.
Retransmission is a form of online video, such as iviTV and FilmOnTV, whereby content is taken live from broadcast and other sources. The streams, captured by digital receivers, are re-encoded (or transcoded), sent to a central server, and then streamed out as an IP multicast. (See Figure 2 on page 22.) Without direct access to the content, off-air (or cable or satellite) receivers must be set up in every market from which the content is accessed. (While the actual mechanisms have not been publicly disclosed and could deviate from the mechanism described here, they are likely to be conceptually the same.)
This type of service is currently under litigation, as the service providers do not have explicit licensing arrangements with the content providers, who have balked at the service providers' interpretation of an implied license to broadcast content. NAB, CEA and a startup company are currently investigating a broadcaster-supportable scheme that addresses the out-of-market coverage issues regarding Internet carriage of local content.
IPTV, or Internet-Protocol TV, is a scheme such as AT&T U-verse, whereby video content is streamed to a STB by means of a subscribed telephone connection, usually twisted pair or fiber-to-the-home. A telco operator will typically use a Digital Subscriber Line Access Multiplexer (DSLAM) at the central office to supply a one-to-one high-bandwidth connection to each subscriber's customer premises equipment (STB). (See Figure 3.)
While this mechanism does not actually use the Internet, it does encapsulate the video data into IP packets similar to those used to relay data over the Internet. With this type of service, the access to content is completely within a “walled garden,” including a service provider-provided EPG that is used to access content. Although an IP connection is used, each subscriber has a dedicated line to the central office; hence, a full packet-switched network is not needed, lowering complexity and bandwidth, and guaranteeing a specific level of quality-of-service.
Hybrid broadcasting, shown in Figure 4, is a technology whereby broadcasters use a combination of OTA and Internet paths to send coordinated content to Internet-connected TVs or STBs. Groups developing services in Europe, Japan and South Korea have described different forms of hybrid broadcasting. Perhaps the most visible of these is a European consortium, operating in concert with the DVB organization under the name Hybrid Broadcast Broadband TV (HbbTV). Among the services demonstrated by the group are “catch-up” TV, video on demand (VoD) and interactive advertising. A specification for HbbTV has been released by ETSI, and some STBs meeting this spec have been shown.
With Web-TV, Internet content is served up to a TV by means of a STB or specially-equipped TV, as shown in Figure 5. Web-like pages, browsing and apps are directly available to TV viewers. Though similar to online video and hybrid broadcast, the experience is not directed at PC delivery and display; the services rely on an improved user interface with which to navigate content, often integrating a proprietary cross-resource search engine that can locate content from both broadcast and Internet sources.
The TV applications can also potentially integrate Internet, OTA, cable or satellite content, forming a rich media experience. In practice, however, the TV or STB merely provides a “seamless” switch between Internet-delivered and OTA-delivered content. A true hybrid broadcast experience, where content from these different sources is synchronized and integrated by the content owners, is not believed to exist on currently deployed devices.
With Widget TV, small applications, such as Intel widgets and Yahoo! widgets, run on a Web TV, bringing content, information and community features from the Internet to the TV. These widgets, which can be pre-installed or downloaded, offer users a way to customize their TV viewing and information access experience. In their simplest form, widgets might pop up an “app” that runs a local process, such as a trivia game; of greater interest to service providers are widgets that redirect the TV to an online website sourcing other content.
One of the issues of concern to broadcasters is the consistent behavior of these widgets across different devices. For this reason, a number of different “widget frameworks” have emerged, but these are currently driven by the developers of the graphics hardware or user interface middleware (such as the browser, often supplied by a separate content distributor). Ideally, broadcasters would like to provide widgets themselves, but this raises the issue of how to make the user experience — and content accessed by the widgets — consistent to users, across different broadcasters. The OTT issue is similarly problematic with Widget TV.
A look ahead
Various committees have studied the topic of enhanced television delivery, going back to the formative days of DTV. One such effort led to the Advanced TV Enhancement Forum (ATVEF) specification, which defined methods to create enhanced content to be delivered over a variety of media, including analog NTSC and digital ATSC. Around the same time, the ATSC developed the DTV Application Software Environment (DASE), which offered overlapping functionality.
For a combination of reasons, including timing and business issues, neither spec took off as an implemented framework. More recently, the ATSC has formed a new Internet Enhanced Television Planning Team (PT-3) to investigate the opportunities brought about by Internet-connected broadcast receivers, and to lay the foundation for future technologies and standards.
As content owners change their businesses to include a greater dependence on the Internet, it is reasonable to expect that broadcasting will evolve in the direction of integrating several forms of content delivery into a seamless experience for both fixed and mobile viewers. Exciting times are ahead!
Aldo Cugnini is a consultant in the digital television industry.
Send questions and comments to: email@example.com