The Future of AM and FM Radio Answering Questions About HD Radio Technology
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p50_AVI0105 12/17/04 4:24 PM Page 50 DIGITAL RADIO The future of AM and FM radio Answering questions about HD Radio technology BY JOHN GARDNER ith a feature known as Tomorrow Radio, iBiquity Digital Corp.’s trademark HD Radio Wtechnology causes one to pause and consider what the future of AM and FM radio holds. So what is HD Radio? Before getting the more con- sumer-friendly name of HD Radio, broadcast audio's next incarnation was dubbed in-band, on channel or IBOC. This system places two digital Fig. 2: Comparison of analog AM and FM to HD Radio AM and FM sidebands on either edge of the exist- (Source: iBiquity Digital Corp.) ing broadcast analog band (Fig. 1). The two tial to introduce interfer- bands can carry up to HD Radio technology employs a proprietary ence, but signal enhance- 150Kbps of digital data codec called HDC that provides near ment techniques from without compromising CD-quality even down to 48Kbps companies like Texas the analog signal. Instruments and iBiquity Most stations plan to Digital can help ensure deploy only 96 of these the full quality of the ana- 150Kbps initially, until they become want to send, the wider the digital log and digital signals. more comfortable with the system. In sidebands and the closer they are to technical terms, the more data you the analog signal. This has the poten- The digital advantage For audiophiles, quality of sound is the paramount consideration. Broadcast radio, especially in the car, just hasn’t been able to match what consumers have come to expect from their home theaters or CD and DVD players. HD Radio technology changes this. With 96Kbps, HD Radio technology doubles the number of bits, reaching near CD-quality sound. There is no static, no impulse noise, and listeners are able to crank up the sound and hear subtleties that they simply could- n’t hear before (Fig. 2). Fig. 1: HD Radio technology places two digital sidebands on either edge of the existing HD Radio technology employs a broadcast analog band, carrying up to 150Kbps of digital data without compromising proprietary codec called HDC that the analog signal provides near CD-quality even down 50 AudioVideo International Reprinted with the permission of Audio/Video International, January 2005 issue p51_AVI0105 12/17/04 4:26 PM Page 51 DIGITAL RADIO ondary, or B, channel that will give stations the abil- ity to offer consumers more diverse content choices. Consider a jazz station that wants to pro- vide more than just music. Some of its listen- ers may want the latest news, traffic and weather, while other listeners complain that these extras are annoying breaks in their music.The station can now serve both listeners by playing jazz on the main channel and news on the supple- mental channel. In this way, a listener who wants to hear about traffic can switch to the supplemen- tal channel. Fig. 3: By delaying the analog signal approximately five seconds behind the digital signal, an HD Radio receiver One of the strongest can buffer up to five seconds of audio. By blending between the analog and digital signals, the receiver can supporters of HD Radio eliminate signal drops up to five seconds long, improving the overall listening experience technology is NPR, which coined the term to 48Kbps and offers superior quality es. Starting with the artist name and Tomorrow Radio for its ability to to existing FM analog. song title, stations can begin to offer broadcast multiple channels of audio “Even demanding engineers noted information feeds providing real-time from one radio station. Starling isn’t as having Golden Ears have quickly news, weather, traffic, sports and stock shy about his excitement. “HD Radio become believers that HDC is far information that will be displayed in is the high growth driver for broadcast better than analog,” said Mike the form of scrolling audio. Numerous studies Starling, VP for Engineering and text on HD Radio conducted over the past Operation at National Public Radio receivers.As HD Radio 15 years show that when (NPR). Starling’s words are based on technology becomes there are multiple sta- extensive subjective audio testing by more established, more Supplemental tions in a market, listen- NPR throughout the summer of advanced services Audio Services ership goes up signifi- 2004, the results of which have been become possible, such would allow for cantly,” says Starling. recently filed with the FCC. In gen- as navigation systems the creation of a With Supplemental eral, and somewhat counter-intu- that can tap into digital secondary, or B, Audio Services, both itively, voice quality is more difficult traffic reports and public and commercial to code transparently than music. reroute drivers around channel to offer FM broadcasters who Jazz quality, for example, has been accidents and other consumers more adopt this technology shown to hold up at 36Kbps with hold-ups. diverse content will be able to double close to CD quality while voice gen- For broadcasters, the choices their broadcast capabili- erally can go as low as 56Kbps with high quality of digital ties without requiring near transparency (Fig. 3). radio offers a com- any new spectrum. pelling business alter- How a station splits the Beyond audio native: the ability to channel actually depends Beyond the improved sound quali- broadcast two distinct streams of pro- upon how they are going to use the ty, HD Radio technology gives broad- gramming on the same FM channel. secondary, or supplemental, channel, casters the ability to lower the bit rate “Supplemental Audio Services” and on the quality they require. for main channel programming and to (pending approval from the FCC) Stations can split the 96Kbps band- introduce exciting new digital servic- would allow for the creation of a sec- width to fit their programming. The JANUARY 2005 51 p52_AVI0105 12/17/04 4:28 PM Page 52 DIGITAL RADIO split could even be dynamic; for exam- Home theater in the car What’s on the horizon? ple, a station could broadcast at One of the most exciting possibili- HD Radio technology is still 96Kbps and then scale back the main ties of HD Radio technology is the emerging. Initial deployments will channel to a 64-32 split to enable a ability to broadcast full 5.1-channel offer superior audio quality, informa- newsbreak on channel B. Surround sound. Many tion feeds, and the potential for a sec- high-end car audio sys- ond content channel. However, it's Mixing analog and Analog also tems already support not hard to imagine where HD Radio digital DVD audio and thus technology can go. Time-shifting will It’s important not to serves as a have the necessary allow a listener to pause a live pro- forget about the analog backup to the speaker configuration to gram or even rewind. The length of broadcast signal. Stations main digital support Surround sound. pause or rewind time will depend will still broadcast con- channel The challenge lies in get- upon how much memory the radio tent over the analog ting 5.1-channel content has available for buffering. Reading channel to reach existing to the radio. services for the blind can provide analog listeners with their primary One method for achieving 5.1- access to newspapers or magazines. content. However, one may ask, why channel Surround sound is the Receivers could buffer broadcast not run alternate content over the matrix approach. The station downloads offering more informa- analog channel, giving stations two or encodes a 5.1-channel track into tion about a subject being discussed three channels instead of just one or 96Kbps stereo. If the HD Radio on the content channel, reducing two? receiver supports loads on station servers. The reason is that the analog also matrixing, it can extract Wireless interfaces serves as a backup to the main digital the 5.1-channel infor- One exciting would allow users to channel, so that if the digital signal is mation. An alternative connect to their home lost for any reason, the system will approach from SRS is possibility of networks for downloads seamlessly blend back to analog with- Circle Surround tech- HD Radio or receiver configura- out disruption to the listener. nology, which converts a technology is tion. Listeners could This is accomplished by delaying the 96Kbps track down to the ability to define the kind of con- analog signal approximately five sec- 80Kbps. This leaves broadcast tent they want to hear. onds behind the digital signal. Here’s 16Kbps for steering Work has already begun what happens when listeners turn on information, telling the 5.1-channel on creating a return their digital radio. For the first five system which sounds go surround sound channel where listeners seconds, they’ll hear the analog signal to which speaker with can press a Buy button (the digital data itself is not delayed what delay. In either to get more information and, for digital services such as news case, if the receiver doesn't support on a product through email. or traffic feeds, the digital data is these technologies, it will ignore the Initial deployment of HD Radio available for use immediately). encoded steering information and technology has already begun with Meanwhile, the radio will listeners still will more than 150 stations across the buffer the digital signal. hear high-quality country broadcasting in digital and When the analog signal stereo. HD Radio receivers available from catches up to the digital HD Radio has Given that there Kenwood, Panasonic and JVC. You signal that the radio has is no formal stan- can hear the quality of HD Radio stored up (to existing already begun with dard for imple- technology for yourself today by vis- AM and FM in this more than 150 menting 5.1-chan- iting www.hd-radio.com for a list of example), the radio will stations across nel audio, it is likely stations broadcasting digitally.