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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
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Codec Bandwidth
Thiscontroladjuststhebandwidthofahighorder,linearphaseFIRlowpassfilter
thatremovesallhighfrequencyenergyaboveitssetting.Thiscontrolpermitstheoutput
audiobandwidthtoberestrictedifrequired,andsettingsbetween4kHzand16kHzare
availablein1kHzsteps.WhenthecontrolissettoitsOFFpositiontheaudiooutput
bandwidthis24kHz,theNyquistfrequencyoftheoutputsection’s48kHzsamplingrate.
Enable
When Enable is selected the
VP‑8
iP
enablesaspecializedhighfrequencymanagement
algorithmthatartisticallyminimizes“splashiness”inthehighfrequencyspectrum.
Such“splashiness”isknowntoexacerbatecodingartifacts,especiallywhentheCodec
isoperatingatverylowbitrates.
HF Protect Freq
WhentheHFProtectalgorithmisactive(seeabove)itwillworktominimize
coding artifacts caused by certain kinds of high frequency program energy. The
HF Protectcontroladjuststhefrequencywherecontrolactionbegins.Thiscontrol
works in concert with the Ceiling
control(below).
HF Ceiling
The Ceiling control adjusts the audio threshold where the HF Protect algorithm will
begintooperate.Themorenegativethecontrol’ssettingindB,thesooner(amplitude
domain-wise)thehighfrequencycontrolwilltakeplace.
A Note About Attack Time
There is no user-adjustable attack time for the HF Protect algorithm. This is because
its
reaction timeisdeterminedautomaticallybyevaluatingcertaincharacteristicsofthe
inputprogramenergyusingFFT(FastFourierTransform)analysisbeforetheenergy
actuallyreachesthealgorithm.Becauseofthecomplexityandcriticalnatureofthis
measurement, and its interaction with other aspects of the HF Protect algorithm, the
reactiontimeisacomplexcombinationoffactorsthatwouldbeextremelydifficult
tocontrol,letaloneoptimize,withknobs,andthereforeithasnotbeenmadefield
adjustable.
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