Algorithm Concerns Slow HD Radio

Has radio's digital rollout hit a slight pause, or a big glitch? That depends on who's being asked.
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Has radio's digital rollout hit a slight pause, or a big glitch? That depends on who's being asked.

Standards-setting activity for IBOC was suspended temporarily in May by the steering committee of the National Radio Systems Committee's DAB subgroup.

After a private demonstration at National Public Radio, several NRSC sources said they found the artifacts in the system using the PAC audio coding algorithm "unacceptable."

In a memo to fellow members of the DAB Subcommittee, the steering committee stated: "DAB Subcommittee members who attended the NPR demonstration do not consider the audio quality demonstrated by the Ibiquity 36 kbps PAC technology to be suitable for broadcast."

A written complaint from the industry standards body at this stage of the digital radio rollout is unwelcome news for proponents. It comes at a time when many radio groups have placed initial equipment orders, receiver makers have established product plans and a handful of stations are on the air.

This development, sources said, puts the onus on Ibiquity Digital Corp. to solve problems related to its codec of choice. Ibiquity can to continue to tweak PAC or chose another audio coding algorithm. The company continues to work on improvements of PAC so the standards-setting process for HD Radio can resume. It said it would continue to work on software upgrades for PAC. At presstime, Ibiquity could not say how long it might take to resolve the issue.

Growing concern about the performance of the PAC codec on AM at low bit rates led the steering committee to make this decision, although members expressed concern about FM as well; and they have questions about how PAC's performance could affect the potential quality of secondary audio channels and ancillary data services.

Some orders affected

Also as a result of the suspension, some major radio groups are slowing adoption of AM IBOC until the codec issue is resolved, according to broadcast sources.

Some vendors said some customers had asked for their equipment not to be shipped while the issue plays out.

Harris Vice President of Transmission Systems Dale Mowry said that while no one had cancelled orders of HD Radio equipment, a handful of "industry leaders" have asked for a hold on both AM and FM shipments.

"These represent a small portion of the IBOC backlog," he said. Harris also said its NeuStar, a codec pre-conditioner meant to enhance digital signal processing at low bit rates for AM and FM, could work with a variety of codecs, not just PAC.

Broadcast Electronics Vice President of RF Systems Tim Bealor said that while some of the major groups were slowing down the rollout on the AM side, BE was still shipping HD Radio systems.

"Everyone who has orders has taken at least partial delivery. ... Certainly, I won't say the codec issue has no impact. Everybody wants to make sure it sounds good. We'll keep an eye on it," he said.

Nautel President/CEO Scott Campbell said, "We'll see how this news affects the rollout."

Clear Channel Radio had been planning to transition one AM and seven FMs this year. The AM station, WSAI in Cincinnati, is on the air, and a Clear Channel source said the company is proceeding with the FM conversions.

The company transitioned one AM primarily to get a feel for how the system would work. "We have concerns on the AM side," said Bill Suffa, senior vice president of capital management.

What next?

In a memo to members of the NRSC DAB Subcommittee, the steering committee stated: "The NRSC has long considered flexibility to be an important feature of IBOC digital radio systems, and is concerned that PAC operating at bit rates between 36 kbps and 96 kbps (the maximum coding rate used in the hybrid FM IBOC system) could also have quality issues that may need to be investigated by Ibiquity."

The steering committee is made up of NRSC Chairman Charlie Morgan, DAB Subcommittee Chairman Milford Smith, Evaluation Working Group Chairman and co-Chairman of the IBOC Standards Development Working Group Dr. Don Messer and Co-Chairman of the Working Group Paul Feinberg.

The steering committee has the ability to render decisions between DAB Subcommittee meetings, according to the bylaws governing the NRSC.

Smith said the NRSC still supports IBOC. "The overall system is really great and works well." Yet, "Our goal from the start has been to have both an AM and FM solution. We don't think we've got an AM solution."

Smith said his employer, group owner Greater Media, is proceeding with antenna modifications for IBOC. However, a source close to the company said, "We're hesitant to flip on the switch until the issue is resolved."

Smith and several NRSC sources said the standards-setting process would resume when Ibiquity has demonstrated the problem is resolved.

Ibiquity has two choices: continue to tweak PAC or choose another audio coding algorithm such as AAC or MPEG. Ibiquity had used AAC previously, and several NRSC sources said they thought the system audio quality with AAC was better than it is with PAC.

Ibiquity declined to give details about the demonstration in May at NPR.

NRSC sources said non-commercial and commercial NRSC station members who attended that demo agree the artifacts are unacceptable. Several said the audio quality on a talk-format example with the system fed through a digital exciter sounded "unnatural."

Members of the NRSC Steering Committee believe the average listener would notice the artifacts and be annoyed by them.

Yet the DAB Subcommittee believes the problem can be fixed. When asked what the FCC might think of the development, one steering committee member said, "We want the FCC to know it's a problem we found, but there's no need for the FCC to raise an eyebrow" over this.

Ibiquity has been working on codec improvements for some time, several sources said. The difference between this discussion now and those that took place a year ago, one vendor said, is that "Now people are asking, 'Is it really getting better?'"

PAC upgrades

In a statement released May 15, Ibiquity responded to the NRSC's suspension. "At this time, we concur with their decision to temporarily delay these efforts until the issue is resolved. ... This issue is in the audio coder and has to do specifically with AM audio quality. The resolution will be a software upgrade, and no other changes to the system will be necessary. We have an on-going improvement plan and anticipate resolution of the AM audio quality issue as soon as possible."

After the news came out, various participants disagreed on what it meant. Some in the proponent camp said the NRSC was basing its action on the hypersensitive ears of a handful of "golden ears," and some broadcast sources argued that many consumers listening in the car environment wouldn't care. Others disagreed, saying the NRSC action was long overdue.

Ibiquity used AAC as the codec for all the previous data submitted to the NRSC, and the technology developer and NRSC members agreed some tests would be re-run with PAC. NRSC sources didn't believe the data would indicate a problem, yet Ibiquity chose not to submit an AM report with PAC earlier in the year, saying it wanted to re-run the tests with a later version of the codec.

The steering committee addressed the codec difference issue in its memo: "Earlier Ibiquity demonstrations of its AM IBOC system incorporating the previous low bitrate coding algorithm at 36 kbps, as NRSC-evaluated, were highly praised by many NRSC members. Nevertheless, Ibiquity has chosen to move forward with its 36 kbps PAC coding technology for use in its AM IBOC system."

Several sources said PAC's performance at low bit-rates has been an issue for quite a while, even though Ibiquity continues to tweak it.

Kenwood, meanwhile, said it is still prepared to go forward with its receiver launch this summer despite the NRSC action.

Bob Law, senior vice president of Kenwood USA, said receiver retailers have gone through this kind of audio quality discussion before, with AM stereo and early FM radios. The key is whether consumers think there's a benefit to having the new technology, he said.

Law believes the issues can be addressed within PAC, without changing codecs. Part of what needs to be done, he said, is to set realistic expectations based on what consumers want.

A broadcast source with a major radio group owner and Ibiquity investor agreed. "In the end, it's the perception of the listener" that counts, he said.

Unclear at presstime was how the standards pause might affect the rollout schedules for chipset makers and additional receiver manufacturers for rolling out more HD Radios in '04.

Ibiquity was expected to release software code to chip and receiver manufacturers soon to keep the HD Radio rollout on track. It was unclear how substantially chip and receiver manufacturers could compress their production schedules to allow for a delay, several sources said.

Broadcast sources pointed to potential consumer perception issues that could arise if the chipset software must be changed after the first generation of HD Radios are on the market and the change cannot be handled without a customer trip back to the retailer.

Also unclear was whether the decision by the DAB Subcommittee would affect the work of a separate NRSC subcommittee developing data standards for IBOC, although in its memo, the steering committee stated, "the poor performance of the PAC codec at low bit rates raises concerns of performance at intermediate rates, such as 64 kbps."

The steering committee said many ancillary data providers and secondary audio providers propose reducing the main audio channel of the digital transmission to 64 kbps in order to provide these services.

"The NRSC is not aware of any testing or public demonstration of the Ibiquity system utilizing PAC at these low bit rates. This is an important matter for the NRSC," given the recent formation of the subcommittee, the group stated.

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