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VP-8IP / Sep 2013
V P - 8
i P
P R O C E S S M O D E S
MP3/ACC
<48
k
Adaptive Bandwidth Controller™ Controls
The
VP‑8
iP
also incorporates an Adaptive Bandwidth Controller™ as one of its tools
for managing the behavior of low bitrate codecs. There are five controls associated with
the Adaptive Bandwidth Controller™ which will be discussed in order.
Codec Sample Rate
The
Codec Sample Rate
control has two positions, 48/32/24k and
44.1/22.05k
which
correspond to different multiband operating parameters within the Adaptive Bandwidth
Controller™.
The differences between the two settings serve important roles in achieving the best
sound from codecs at different sample rates. We recommend utilizing the 48/32/24kHz
or 44.1/22.05kHz position for codecs operating at those sample rates. Sample rates lower
than 22.05kHz may benefit most from the use of the 44.1/22.05kHz setting.
Low Pass Filter
The purpose of the low pass filter is to remove program energy higher than the
frequency selected by the control. By removing audio energy above a certain frequency,
higher subjective audio quality can be achieved by the codec when operating at a particular
bitrate. Low pass filters become especially important at very low bitrates because they
remove energy that the codec does not need to contend with in order to provide a pleasing
listening experience at the decoder output (we consider any bitrate below 32kHz to be
very low).
The graphic at
right is a family of
sweeps displaying
the characteristics of
the Low Pass Filter
when set at each of
its available cutoff
frequencies.
Note the steep
low-pass character-
istics and the perfect
ruler-flat passband
flatness at each filter
setting.
