New Media Technology Omnia ONE Multicast - Manual (Page 10)

OmniaONE Multicast - Use and Operation Manual – Version 0.90
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and bandwidth limiting methods that were required for analog broadcasting, as well as for the signal
normalization techniques used in recording and mastering.
Audio codecs on the other hand are moving targets - each codec algorithm has its own set of
artifacts. So not only does the sonic quality vary depending on the algorithm and bitrate used, but
more importantly they vary in their ability to mask their own coding action. This is why we call it a
‘moving target’, and is why conventional audio processors fall short in a coded audio environment
and can actually make coding artifacts worse due to their inability to adapt appropriately to the
changing operation of the codec as the program content changes.
Prior art in audio dynamics processing could only address some of the challenges of provisioning
audio for coding. This hurdle existed because the codec adapts to the incoming program (so as to
generate the least amount of output data representing the input audio) causing the sonic artifacts
generated by the process to continually change. Unless the audio processor can predict these
changing characteristics of the codec, it can’t possibly create output audio that is perfectly tailored
for the coding process.
Conventional processors utilize rather simplistic high frequency limiters and fixed low pass filtering
that does not change with the program material. When these less intelligent processors feed a codec
the audio might sound acceptable one moment and offensive the next. Because they cannot “know”
what the codec will do next, the result is over-compensated, dull and lifeless audio… audio that still
contains objectionable codec-generated artifacts!
OmniaONE Multicast and HD
® Radio
The advent of HD Radio R has introduced the capability to transmit multiple program streams, or
“Multicast”, within a single 96kbps digital broadcast data channel. To facilitate this, multicast relies
on the use of codecs with comparatively low bitrates. A broadcaster can choose to transmit a number
of multicast channels and select the bitrate for each one. However, the more multicast channels there
are, the lower the bitrate each channel must have in order for them to all fit within the total available
bandwidth.
In the very near future, many low bitrate multicast audio channels might exist. To achieve maximum
sound quality, the kind that attracts and holds listeners, those channels will need specialized
dynamics processing capable of creating great sound regardless of program content and bitrate.
They will need Sensus
®.
OmniaONE Multicast was designed from the ground up for provisioning audio for codecs operating
at these low bitrates. With Sensus
®, the innovative algorithm inside OmniaONE Multicast, it is now
possible to have consistently high audio quality with a minimum of codec-induced artifacts.
OmniaONE Multicast creates highly listenable audio lacking the dull, muffled, ‘swirley’ sound
usually associated with codecs operated at extremely low bitrates.