Several sources close to HD Radio development say Ibiquity Digital Corp. is close to a decision on whether it will change codecs – and that the industry should know something more definitive by the end of this month.
Broadcast sources said the company is pursuing parallel paths, still working on improving the performance of its Perceptual Audio Coder at low bit rates, yet also running tests to compare its system using both PAC and aacPlus compression algorithms. Some of these sources presumed the company was trying to reach a licensing agreement with Coding Technologies over the use of aacPlus.
Observers differed over whether Ibiquity and Coding Technologies could reach an agreement that made business sense for both companies. Even if they did, said observers, unknown at press time was how dropping in a new codec might affect the transmission and receive ends of the HD Radio system, and how long it might take to work out any glitches that might occur along the way.
Ibiquity would not comment on the rumors. A spokeswoman said the company continued to work on a software fix for the AM audio quality. “We have nothing to announce now.”
When Ibiquity does decide to go public with what path it has chosen to pursue, it must inform the DAB Subcommittee of the National Radio Systems Committee. In May, the group’s steering committee temporarily suspended standards-setting activities for Ibiquity’s AM and FM system. The group doesn’t believe PAC on AM at 36 kbps is suitable for broadcast and has questions about its performance at intermediate levels below 96 kbps for FM.
NRSC Spokesman John Marino, vice president, NAB Science and Technology, said, “We have no new information on the future of PAC – whether Ibiquity is continuing to work on improvements to PAC, or whether they intend to implement another codec.”
Once Ibiquity makes a decision, Marino said, “It’s up to them to prove they’ve fixed the problems at low bit rates. … They have to prove they’ve fixed the problem to the satisfaction of the NRSC.”
There would be more steps with the NRSC after that.
“If they do switch, or if they tweak PAC, they would have to come back to the working group with another series of audio test results,” said Milford Smith, Chairman of the NRSC DAB Subcommittee. “It was always in the evaluation plan, they’d have to re-run the tests (with the final codec), to make sure changing the algorithm has not negatively impacted the audio system.”
He said the format of the test has already been developed by the NRSC. The standards-setting body would be looking for Ibiquity to have the tests done with an NRSC observer. Smith said such new tests could be conducted and evaluated by the NRSC “in a relatively short period of time.”
Antenna options explored
Meanwhile, an ad hoc NAB group working on antenna solutions for HD Radio was close to filing a letter with the FCC in late June to request approval for the so-called dual antenna transmission implementation for FM stations using HD Radio. Marino said stations would still need to request Special Temporary Authority for this antenna scheme, but they would not need to purchase a combiner nor modify their transmission system.
“If they have an auxiliary antenna and transmitter that meet the criteria, they could just plug in an IBOC transmitter and go with it.”
In its interim authorization for HD Radio, the FCC allowed only certified single antenna implementations.
Marino believes the FCC would approve the concept. NAB planned to submit test data to the commission to support its premise.
“It will help these stations get on air quickly,” he said.
Ibiquity continued to work on AM nighttime interference studies in June. The technology developer met with an ad hoc NAB committee in June to review test results from two studies: a computer modeling to predict groundwave interference at night on AM and field tests on AMs WLW in Cincinnati and WOR in New York to study skywaves.
Ibiquity Vice President and General Counsel Al Shuldiner said the computer modeling report is complete and Ibiquity was still working on the field test report. “They want to see the whole package before they do anything,” he said of the committee. Ibiquity hopes to have that work completed by the end of this month.
The pause in standards setting has been felt at the FCC, where notifications for stations converting to HD Radio has dropped off, said a staffer. (See our station conversion list on page 12.)
Other companies have taken advantage of the pause in HD Radio standards setting to publicize their technologies.
APT is looking for stations in the U.S. willing to use its apt-X compression algorithm to “enhance” their analog and digital audio if they use HD Radio technology. Spokesman Jon McClintock said, “We think apt-X has a place in the broadcast chain.”
Some radio groups in the U.K. that have implemented Eureka — 147 use apt — X as their codec. McClintock said apt-X should be used farther up the chain than PAC, before the signal reaches the transmitter. “We don’t want to compete against Ibiquity. We want to complement them.”
Since apt-X uses adaptive differential pulse code modulation, he said, it’s not a psychoacoustic masking algorithm, and therefore less destructive to the audio, he said.