|
 The
Future is Now
DAB. IBOC. "HD Radiotm."
Eureka 147. DRM. Whatever you call it, digital radio is here.
Aside from its digital nature, what
changes will DAB bring to radio listeners and broadcasters?
Consider this, from the Eureka
Consortium:
"[Listeners can] receive the
terrestrial Digital Audio Broadcasting programs using solely
a tiny non-directional stub antenna... receive CD-like
quality radio programmes even in the car without any
annoying interference and signal distortion. DAB radio is
designed for the multimedia age: DAB can carry not only
audio, but also text pictures, data and even videos.
Or this, from iBiquity
Digital:
"In-Band On-Channel (IBOC)
Digital Audio Broadcasting is a method of transmitting
compact-disc-like quality audio signals to radio receivers
along with exciting new wireless data services, such as
station, song and artist identification, stock and news
information, local traffic and weather, and much more. This
new digital broadcast technology allows existing radio
stations to use the current AM and FM spectrum to transmit
analog simultaneously with new higher quality digital
signals that eliminate the static, hiss, pops and fades
associated with today’s reception."
DAB and HD Radio are generally
20kHz audio bandwidth (as compared to FM's 15kHz) which
requires a processor that can sample at higher frequencies, 48 kHz or
higher. Some digital processors with lower sampling
rates are incapable of accurately reproducing this extended
bandwidth.
Besides bandwidth capacity, audio
processors for HD Radio and DAB require an entirely different approach to
maintaining peak levels than traditional RF broadcasting. Due
to the nature of audio coding algorithms, ordinary clippers can
produce undesirable artifacts. All Omnia "EX" processors
for DAB / HD have a
specially designed final stage that not only increases signal
density, but do so in a way that is optimized for bit-reduced
coders.
So, if HD and DAB offer more bandwidth, why
is audio processing still necessary? There are a few reasons:
-
In areas of diminished signal
strength, DAB and HD receivers switch from digital to analog
mode. Audio processing is needed to soften the perceived
quality difference between the two modes.
-
Conditioning the audio prior to
encoding reduces perceived artifacts induced by the
transmission system.
-
To maintain a
"signature sound" - loud and well-defined - in
the new medium.
Omnia has been intimately involved
with HD Radio (in the US) and DAB (in Europe and elsewhere) for many years.
Omnia processors are used on high-profile Eureka equipped
stations and network broadcasters (such as Virgin Radio).
We've been involved with iBiquity since its beginnings
as USA Digital Radio and Lucent Digital Radio, and Omnia processors are key
components of HD Radio tests conducted with broadcasters throughout
the US.
Telos and Omnia have the largest team
of Digital Signal Processing experts in the broadcasting
industry, with years of experience in the science of
optimizing audio for use with bit-reduced codecs. We pioneered
the use of DSP for broadcast telephone applications, were
first to introduce MP3 to US broadcasters in the
groundbreaking Zephyr ISDN
Transceiver, and have
significantly advanced the art of using DSP for broadcast
audio processing applications.
For more information on DAB and HD
Radio, we
recommend visiting these resources:
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