Host Compatibility | Listening Reports filed to FCC on HDC coders | Tomorrow RadioSM Field Testing | FM IBOC Evaluation Report
(posted November 5, 2004) This study is intended to determine the effect of adding the Extended Hybrid Mode to IBOC DAB Primary Mode transmission on stereo and SCA reception of the Analog Host. This study was motivated by National Public Radio’s desire to expand the capabilities of IBOC DAB transmission to support audio information services and other data streams for the public. Since Extended Hybrid Mode transmission adds additional OFDM carriers to the Primary Mode digital spectrum, NPR sought to test this mode’s effect on consumer stereo receivers as well as FM SCA subcarrier radios. This test procedure is commonly referred to as Analog Host Compatibility measurement of IBOC DAB.
National Public Radio ("NPR") hereby submits a report relating to the
iBiquity Digital ("iBiquity") HD Radio™ system entitled Host Compatibility Measurements for the
Extended Hybrid Mode of IBOC Digital Audio Broadcasting. NPR, with support from the Corporation
for Public Broadcasting ("CPB"), conducted the testing to assess the suitability of the iBiquity
HD Radio Extended Hybrid Mode for the transmission of radio reading and other specialized services.
Specifically, the testing measured the extent to which adding the Extended Hybrid Mode to IBOC
DAB Primary Mode transmission affects stereo and SCA reception of the analog host.
---from the cover letter to the FCC submitting the two reports
(posted October 27, 2004) NPR recently filed two reports with the FCC providing advanced research on the HDC coder (tested at multiple bit rates from 16 kbps through 96 kpbs) as well as best performing coders operating within 11.8 kbps and 24 kpbs, the data rates for one and two extended hybrid partitions respectively.
We believe these reports, comprising over a hundred listeners and thousands of hours of listening time, fairly represent the audio performance capabilities of the HD Radio system. The reports indicate the need for licensee flexibility in assigning variable datarates based on program type, and reveal great promise for adding radio reading services within the extended hybrid partitions with much better audio quality than currently available with analog FM subcarriers.
A third report, documenting measurements taken in a variety of analog FM receivers, shows a few dB of increased noise in some receivers when adding two extended hybrid partitions (24 kbps of payload). That report is being finished now and will be posted shortly.
The multiple bit rate testing examined the extent to which general public listeners could detect quality differences in the HD coder at particular bit rates. As we previously reported, NPR's initial Tomorrow Radio Project testing was performed with channel bit rate allocations of 64 kbps Main and 32 kbps Supplemental. See Tomorrow Radio Field Testing in the Washington, D.C., New York City, San Francisco, and Los Angeles (Long Beach) Radio Markets, MM Docket No. 99-325, at 1, filed Mar. 10, 2004. The new testing indicates that 48 kbps is perceived by most listeners as providing equal sound quality to the maximum rate of 96 kbps. Just as importantly, the testing demonstrates that the optimal bit rate allocation varies according to specific categories of programming, including voice and different genres of music.
---from the cover letter to the FCC submitting the two reports
The Report on Perceptual Tests of Low- and Very Low-Bit Rate Codecs results from testing NPR commissioned in cooperation with the International Association of Audio Information Services and iBiquity to assess the suitability of the Extended Hybrid digital spectrum for radio reading service transmission. Specifically, the testing measured subjective qualitative differences among the latest digital audio codecs that may be used for radio reading services.
---from the cover letter to the FCC submitting the two reports
Posted January 22, 2004
Successful Testing of Supplemental Audio Channel Concept in
Los Angeles, San Francisco, New York and Washington, DC Proves the Technology
is Viable
LAS VEGAS - NPR® (National Public Radio), Kenwood USA and Harris Corporation,
Broadcast Communications Division today [ January 9, 2004 ] revealed the complete,
positive results of the 2003 Tomorrow Radio Project field test on supplemental
audio channel (SAC) broadcasting to the National Radio Systems Committee. Tomorrow
Radio's 2003 field tests prove that multiple program channels are fully attainable
using iBiquity's HD Radio FM digital system.
"Multi-casting on SACs is real, and it works better than we anticipated," said
Mike Starling, NPR's vice president for engineering and operations. "HD radio
is no longer just a hypothetical construct. Tomorrow Radio is here today."
Read the 2003 Field Testing of Tomorrow
Radio Report from Hammett & Edison, Inc. (Acrobat
.pdf 7.4MB)
Read the NPR Press Release from January 9, 2004 describing the process
Archives Posted December 7, 2001
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FM IBOC Test Data Report (from iBiquity/ATTC/Dynastat, served on NAB's Science and Technology page)
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