Here Comes Surround
Hot debate over new service for radio promises to enliven weekend
session.
* Sunday morning, April 17: "Surround Sound - A New Frontier
for Radio"
* Sunday afternoon, April 17: "HD Radio Technology"
by Cris Alexander
Few topics have burned up the pages of Radio World in recent
months as much as surround sound. That's also the focus at NAB2005
of a Sunday morning series of Broadcast Engineering Conference presentations.
An afternoon session looks at HD Radio issues. Here's a rundown
of radio engineering-related sessions on Sunday April 17.
All around you
"Surround Sound - A New Frontier for Radio" is
to be chaired by Milford Smith, vice president of engineering for
Greater Media and winner of this year's NAB Radio Engineering Achievement
Award.
Surround has already shown up in real-world HD Radio situations.
But what is involved in implementing surround for a typical broadcast
station, and is it worth it?
"There is a lot of buzz going around that surround sound
might just be the 'killer app' for HD Radio," Smith told us.
"I'm not ready to make that prediction quite yet, but I do
think it is a very attractive technology to both listeners and receiver
manufacturers and has the potential of being implemented at a relatively
rapid rate because of that attractiveness."
He continued, "I think the real implementation hurdle is the
number of currently incompatible systems. At the moment, it would
be a bit difficult to decide on which one to implement with any
certainty that it would be 'the' system or at least the dominant
system. System architectures also vary, some are completely matrixed
based within the two stereo channels ... others have supplementary
steering information that needs to be transmitted," Smith said.
"I am glad to see the NRSC DAB subcommittee start up a surround
sound working group to take a look at these systems, collect the
relevant information and better inform all of us as to their capabilities."
Frank Foti, president of Omnia Audio, is one who thinks surround
sound may be the "killer app."
He leads off the morning with his paper, "The Killer App
for FM: Distinct 5.1 Surround Sound." His presentation
introduces a spatial audio coding system developed by the Fraunhofer
Institute that takes advantage of current research in aural perception.
The system is the only one so far to provide a distinct multi-channel
listening experience to the FM radio audience, he says.
"HD Radio needs a 'wow' factor for the FM IBOC system, and
5.1 surround is it," he said. "Of importance, though,
is that our industry chooses the best system for this technology.
This session will reveal the strengths and weaknesses of the various
surround methods."
"HDC Surround, 5.1 Surround Over HD Radio" is
the title of a paper written by Jonas Röden, Senior Research
Engineer for Coding Technologies Sweden.
David Frerichs, vice president and U.S. general manager of Coding
Technologies, will present the paper and explain the technical basics
of the 5.1 surround system developed by his company and Philips.
He will show how a high level of quality can be achieved and explain
how HDC Surround fits into the bigger picture of radio.
"Digital radio should not be limited to an analog solution
for surround sound," he said. "HDC Surround is a fully
scalable, digital system built by Coding Technologies, the brains
behind the current HDC codec used in HD Radio. With HDC Surround,
broadcasters can go from minimal steering to full steering, maximizing
the quality according to the available bandwidth.
"Analog matrix and watermark solutions just cannot reach the
'data rate' required to provide a satisfactory surround experience.
Instead of saddling a new radio system with old, limited technology,
we should embrace a fully digital, scalable technology for digital
radio," he said.
"5.1 & 2.0 Interspersion: A Reality" is to
presented by Robert Reams, CTO, co-founder and chief scientist for
Neural Audio Corp.
Reams will discuss the interspersion of legacy 2.0 and 5.1 content
and says failure to deal with this on a system basis will result
in transition problems. He will present Neural's spatial compression
and rendering methodology, which allows the distributor or broadcaster
the ability to capture original source 5.1 content and "downmix"
it to a 2.0 channel format while giving consumers the option to
render the content in any spatial format they choose.
"Widespread acceptance of 5.1 radio broadcasting isn't as
far away as once thought," he said. "2.0 and 5.1 content
interoperability doesn't have to be scary, expensive or dangerous.
Modern digital signal processing can modernize the 'workhorse' content
distribution infrastructure every bit as effectively as replacing
it. The key is planned, staged transitioning from where the broadcaster
is now to where the broadcaster wants to be at a rate of adoption
that makes tactical and fiscal sense."
Shigeru Aoki, R&D engineer for the Japan FM Network, is scheduled
to present "The Surround Sound Program for Radio." Aoki
plans to discuss his experiences with putting 5.1 surround on the
air on his network in both digital and analog services and show
how 5.1 can be encoded onto analog FM stations. Note that at press
time, this speaker said his attendance in Las Vegas was uncertain.
Digital in the real world
"HD Radio Technology" will be the topic for the
afternoon radio engineering session, chaired by Norm Phillips, technical
operations manager for Susquehanna Corp. in Dallas, and Chriss Scherer,
editor of Radio magazine.
Phillips is a strong supporter of HD Radio and thus a natural choice
as chair.
"The audio improvement of a well-done FM HD Radio station
is a total lack of multipath-induced noise," he said. "The
installation of HD transmitters can be very simple or extremely
complicated, depending on the amount of knowledge and planning an
engineer begins with.
"This session will not only present some new technology but
will have over an hour of HD Radio installation case studies from
five markets. Low-level, high-level, combined antenna, split-level,
electrical needs, HVAC and other issues will be covered."
Addressing HD Radio STL issues is Sunil Naik, engineering director
of Moseley Associates. In "Hitless Space Diversity STL Enables
IP and Audio in Narrow STL Bands," Naik will discuss means
of transmitting a 300 kbps IP channel alongside a 44 kHz stereo
pair within a 300 kHz STL channel. He will present a new transfer
panel that allows "hitless" switching for real-time implementation
of space-diversity antenna systems for 128 QAM.
"Linearizing HD Radio Transmitters - A Technology Survey"
will be presented by Anders Mattsson, principal engineer at Harris
Broadcast Communications. Mattsson will cover advanced equalization
techniques, including Volterra-based and Neural-based equalizers.
In addition, the differences between baseband and RF pre-distortion
and their respective advantages and disadvantages will be discussed.
Henry Downs, associate principal electrical engineer of custom
RF products for Dielectric Communications, will present "IBOC
Considerations for Multichannel FM Installations."
Downs plans to discuss the combining of multiple analog and digital
signals into a common antenna, with an emphasis on site-specific
solutions.
"The key to successful HD Radio implementation is the minimization
of the losses incurred when the existing analog signal is combined
with the new digital sidebands," he said.
"In the case of a multi-transmitter site with a master antenna,
the least lossy solution offered is to effect combination of the
analog and digital portions of the signal in the antenna itself."
"Split Level Combining Explained" will be presented
by Steve Fluker, director of engineering for Cox Radio in Orlando.
"In order to understand this technology, it's important to
have a good understanding of just what HD Radio is, how it works
and what combining is." He plans to explain "how the analog
and digital signals are basically two separate radio stations and
the challenge is how to transmit both carriers at the same time."
Jerry Westberg, senior design engineer for Broadcast Electronics,
will talk about his paper, "4M Modulation and Its Benefits
on Digital Radio."
Westberg will discuss limitations of PWM transmitters trying to
pass an IBOC signal and how these limitations can be overcome by
using a DSP-based 4M modulation scheme with no PWM filtering. The
result is much higher quality in both the digital and analog domains,
the company argues.
"HD Radio Installation - Two Case Studies" will
be presented by Erick Steinberg, director of technical operations
at Susquehanna Radio San Francisco. Last year, Susquehanna installed
HD Radio systems at three of its Bay Area FM stations. Steinberg
will discuss his experiences with the high-level system used for
KFOG and the low-level system on KSAN.
Paul Shulins, director of technical operations for Greater Media
in Boston, will discuss his HD Radio experiences in "HD
Radio at Greater Media Boston." Shulins will discuss his
research and data collection techniques for measuring the coverage
of the HD Radio signal, correlating it with the analog signal and
local topography. He will discuss leveraging the investment in HD
Radio transmitters to provide benefits to the analog systems already
on the air.
"Improving Transmitter Linearity in FM HD Radio Using Digital
Adaptive Pre-Correction" will be covered by Tim Hardy,
head of development for Nautel Ltd. Hardy will cover the theory
of pre-correction in general and will go into detail on the adaptive
system.
"The advantage of adaptive pre-correction is in its ability
to keep the emissions below the mask under changing conditions,"
he said. The paper will include measured results that he says demonstrate
that fixed pre-correction cannot guarantee compliance in certain
real-world situations while the adaptive system is compliant in
those same situations.
Derek Kumar, vice president of engineering for Digital Radio Express,
will present, "A New Approach to Digital Radio Broadcasting
in the FM Band." In his paper, Kumar will introduce a new
digital FM subcarrier technology promising an order of magnitude
increase in data throughput and reliability.
"This is accomplished by using state-of-the-art digital modulation,
error correction coding (turbo coding), equalization and audio compression
(world standard aacPlus v2 technologies)," he wrote.
Also on tap Sunday, in addition to the above sessions, Charles Morgan,
the senior vice president of Susquehanna Radio Corp., will provide
an update of activities at the NRSC in a morning talk.
In the afternoon, Don Messer, director of the Spectrum Management
Division of International Broadcasting Bureau, speaks about "The
DRM Digital Modulation System: Performance in the AM Band, Including
Comparisons with Amplitude Modulation."
|
