Digital radio can deliver exciting new revenue streams to broadcasters by leveraging data and file transfer capabilities that will enhance the listener experience with multimedia elements such as album art, liner and programming notes, news, weather, traffic and sports to broadcasts. Because of its low cost, large footprint and ubiquitous nature, digital radio's bandwidth may also be made available for subscription services.
Figure 1. The complete audio and data signal flow of the HD Radio system
Data and multimedia capabilities have been designed into all DRB systems, including HD Radio, from the beginning. There are well-defined standards for data and multimedia applications that allow for the development of Application Program Interfaces (APIs) within the transmission and receiver ecosystems. Several HD Radio applications have already been developed and deployed.
An album art application provides the ability to deliver JPEG, GIF and PNG8 images synchronized with audio programming on HD Radio broadcasts. A Software Development Kit (SDK) for receiver partners is available from iBiquity and has already been implemented in new JVC receivers. Clear Channel is currently testing this capability in several markets. This function, now called Artist Experience, was demonstrated by iBiquity at the 2010 Radio Show.
Traffic services provide textual and graphic traffic and transportation system information in standardized transmission protocols. These can be displayed on enabled HD Radio receivers or overlaid on GPS navigational systems equipped with the HD chip set. Clear Channel's Total Traffic Network and The Broadcast Traffic Consortium provide these services to subscribers in many markets.
Journaline 3, developed by Fraunhofer IIS and deployed by Clear Channel in the United States, provides hierarchically structured information that the user can access on topics of interest in a magazine type format. Menus and text content are encoded in JML (Journaline Markup Language) for transmission to subscribers' HD Radio receivers.
Electronic program guide (EPG) offers users the ability to navigate, select, and discover content by time, title, channel and genre from an onscreen graphical program guide. IBiquity has developed an EPG data structure and client application specifically for HD Radio. Field trials of the overall EPG ecosystem for U.S. radio broadcasting are now underway, with funding and management provided by the NAB Fastroad program.
Conditional access provides pay-for-play and other restricted access services. The conditional access architecture for HD Radio easily integrates into the HD Radio system. The conditional access unit at the station scrambles the data streams and entitles specific radio receivers to access the content by addressing the receiver's unique electronic serial number (ESN).
Push radio is another exciting new technology that will send podcasts and other specific information and targeted programming directly to the listener's digital radio over the air, without the need for an Internet connection. This technology is currently being developed by Beijing Jolon and Commercial Radio Australia for use on the DAB+ system. There is interest in developing this concept for HD Radio.
Data transmission system
The Importer is responsible for multiplexing all of the Advanced Applications Services (AAS), supplemental audio (HD2, HD3, etc.) and data services presented to it by the audio and data clients. The data services are encoded separately from the audio stream via the Radio Linking Subsystem (RLS) and are multiplexed into the Importer to Exporter (I2E) IP stream for transport to the Exporter.
Currently, the HD Radio stream can carry up to four streams of digital audio. The number of simultaneous data streams varies depending on available bandwidth, the data protocol used and the logical channel employed. Consideration must be given to the delivery time requirements of the data and available bandwidth. More bandwidth can be allocated to the data services at the expense of audio service bandwidth if faster delivery and/or larger file sizes are needed.
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