ATSC 2.0: Open MediaHub Concept
Combining strengths of broadcast and Internet delivery technologies to provide a central, transparent mechanism for supplying high-quality broadcast content to any device connected to the home network
By MARK CORL
Chief Technology Officer, Triveni Digital
To both hasten the acceptance of the new standard and to verify that the services defined are viable, the anew ATSC 2.0 Implementation Team (comprising CE representatives, broadcasters and industry suppliers) is working hard prior to the standard’s completion so that viable working implementations of the standard may be identified and promulgated when the standard is ratified.
To begin validating the ATSC 2.0 features and functions quickly, the implementation team is developing a conceptual device known as the “ATSC Open MediaHub.
As a reminder, key features of the ATSC 2.0 backwards-compatible suite of standards will include, among other things:
–Mechanisms for carrying other types of encoded video and audio such as H.264 and HE AAC within the broadcast dramatically improving compression and, thus, the amount of content that can be carried;
–Triggers which can signal events to receivers, and;
–Object transmission, including URL references and other non-real-time (NRT) data objects.
The Challenge of DTV Diversity
The world of television is changing. Viewers are consuming content on a variety of devices—whatever, whenever, wherever and however they want it. Consumer demand for video content has resulted in an increasing number of distribution methods (cable, satellite and the Internet) to deliver this content to viewers. To date, these conduits, even though they may be supplied by the same provider, are functionally separate.
The trend of more devices used to watch video over many different paths has been evident to television broadcasters for years. Broadcasters have historically controlled a large over-the-air transmission system. This system is extremely effective at delivering video content and has been doing so for over 70 years. In light of the growing number of content delivery alternatives, broadcasters have an opportunity to leverage their broadcasting capabilities to take advantage of the different data delivery models.
While the multiple paths of content delivery, multiple viewing devices and changing viewer behavior may appear to be an insurmountable challenge for the television broadcasters, these irreversible trends also offer a very large opportunity. Broadcasters have significant popular content delivered over their own terrestrial broadcast system and through cable and satellite providers.
Broadcasters also deliver content through their Web sites where consumers can obtain video content at any time. However, broadcasters must pay significant amounts of money to transmit various content through an ISP and, often, through a content delivery network (CDN) in the case of audio and video content. Unlike terrestrial broadcasting, the cost of CDN distribution is variable, increasing with each additional viewer. In addition, the broadcasters’ content is often lost in the vast amount of available content on the general Internet. Potential viewers often have difficulty finding local content that may be of interest to them. No longer are broadcasters simply competing with the other channels over the air or on the cable network, now they are competing with the entire Internet and all of its distractions.
New Opportunities with ATSC 2.0
The ATSC 2.0 standard fully comprehends the availability of Internet connectivity in the future viewing environment. Whether via connected TVs or hand-held devices connected to the home WiFi system, the availability of Internet access is a key feature of many of the services defined by the standard. Fundamentally, this is a departure from past attempts to extend broadcast television standards since it does not assume a single delivery path for content. Thus, a hybrid delivery system is described with the best features of broadcast combined with the point-to-point nature of the Internet in whatever path it is made available.
The Open MediaHub architecture combines the strengths of broadcast delivery with standard Internet delivery technologies. The intent of the MediaHub is to provide a central, transparent mechanism for supplying high-quality broadcast content to any device connected to the home network. A key component of the Open MediaHub is a content caching mechanism that is an important concept in the overall architecture.
The Open MediaHub can perform other ATSC 2.0 receiver functions that are advantageous in a central network location. Primary among these is extracting and forwarding trigger information.
The MediaHub design, shown in Illustration 1, contains a terrestrial broadcast receiver (Data Receiver) and an Internet connection (WAN). Central to the design is the Transparent Proxy that manages how content access requests from the various devices connected to the Home Network (LAN) are fulfilled.
A typical transparent proxy caches requests in a local network storage cache so that subsequent access would not require fetching the same content from the Internet again. Many of these transparent caching systems can access other Internet caches through an Internet Cache Protocol (ICP). In the case of the MediaHub, an additional Cache Manager is defined that manages information received from the broadcast path.
If a local device, for example, the Connected ATSC 2.0 DTV, requests content from the Internet that is present in the Broadcast Cache, then the system will automatically return that content instead of content from either the Network Cache or the Internet itself. In this way, broadcasters can “pre-position” various content, such as local news video, in the broadcast cache assuring that when a user attempts to access that content on the Internet they will receive the pre-positioned content instead.
The broadcast cache content is pre-positioned by transmitting it over the broadcast channel using the standard ATSC NRT datacasting mechanisms. Once in the cache, the content can be delivered to other devices in the home via other content transmission standards such as DLNA (UPnP). Control metadata transmitted with the content determines what standards are appropriate and which HTTP requests should be intercepted by the proxy. This metadata originates from the broadcast side where it is collected from the various ingest mechanisms, formatted and transmitted within the NRT data stream.
The Open MediaHub modules can operate on any type of hardware and can be distributed throughout the home network. A reference implementation comprised of a wireless router with attached storage, an integrated ATSC receiver device allowing off-air reception, and Open MediaHub software is being constructed as part of the ATSC 2.0 Implementation Team activities.
Implementing the Open MediaHub modules on a wireless router places the functions in the optimal position within the home network. Typically, most wireless routers are connected directly to the cable modem or other ISP gateway. Every device in the home—whether wired or wireless—uses the router to gain access to other devices within the home and the Internet. Every access can be processed and perhaps redirected to one of the local caches. Any other media protocols, such as DLNA (UPnP), are also accessible from any device on the network with limited configuration.
Open MediaHub Advantage
By pre-positioning content on the MediaHub, broadcasters can avoid data charges from CDNs and bandwidth changes from their ISP. Any content accessed from the broadcasters’ web pages can be pre-positioned with higher quality at lower cost than can be delivered via the Web. Broadcasters could also pre-position content from other providers for a fee. Unlike an Internet acceleration service, broadcasters decide what content will be placed on the MediaHub and can optimize that content to match specific business imperatives.
The impact of the Quality of Experience (QoE) realized by consumers with pre-positioned content should not be underestimated. Typical QoE metrics are derived from a combination of content delays including initial time to view and buffering delays as well as the typical video quality metrics such as resolution and transmission-induced artifacts.
A recent study showed that many consumers abandoned viewing content when startup delays exceeded more than five seconds for short form content. And roughly half the time they would abandon viewing content if they perceived issues with delivery. In an environment with so many choices, broadcasters can ill afford to lose viewers based on delivery issues. By caching content directly into the home environment on the MediaHub, broadcasters can avoid many of the issues associated with delivering content over the open Internet thus improving the QoE and retaining viewers.
Also note that with an extended MediaHub implementation, DVR-like functionality can be added to the device, caching content received directly from the linear broadcast instead of using additional bandwidth for NRT. This content can then be made available to home devices through either a Web or DLNA interface—just like the content broadcast on the data channel. In fact, if segmented correctly, the broadcaster could supply alternative content for various segments. This could be used to replace advertisements or to create targeted advertisement. Access to this content via Web accesses or DLNA would appear linear but would be seamlessly selecting from a variety of disparate segments.
An Open MediaHub reference implementation is being constructed using off-the-shelf components with custom ATSC 2.0 software. This platform will offer a way for the implementation team to quickly instantiate various features and functions of the ATSC 2.0 standard without waiting for comparatively long CE product development cycles. This will allow full end-to-end testing as well as experimentation with various business concepts. In the meantime, the ATSC 2.0 standard itself is currently under development, with completion of final elements expected later this year. A number of key pieces of ATSC 2.0 have already been finalized, including the Non-Real-Time Standard (A/103) and advanced video and audio codecs (A/52 and A/72).
The ATSC thanks Mark Corl, Chief Technology Officer of Triveni Digital and a participant in the ATSC 2.0 effort, for this comprehensive look at the proposed ATSC Open MediaHub, which could be a key element of the updates to the U.S. digital TV standard with new, yet backwards-compatible, functionality.