- Dolby Multichannel Audio Tool User's Manual

Dynamic Range Control
Dolby
®
DP570 Multichannel Audio Tool User’s Manual 87
DolbyDigitalconsumerdecodersnormalizetheaverageoutputlevel—thatis,theoutput
levelaveragedovertime—to–31dBFS(31dBbelow0dBfull‐scaledigitaloutput)by
applyingashiftinlevelbasedontheDialogueLevelparametersetting.
Whenadecoderreceivesaninputsignalwithadialogue
levelof–31,itappliesnolevel
shifttothesignalbecausethisindicatestothedecoderthatthesignalalreadymatchesthe
targetlevelandthereforerequiresnoshift.Incontrast,alouderprogramrequiresashiftto
matchthe–31dBstandard.Whenthedialoguelevelparametersetting
is–21,thedecoder
appliesa10dBlevelshifttothesignal.Whenthesettingis–11,itappliesa20dBlevelshift,
andsoon.
A Simple Rule:
31+(DialogueLevelvalue)=Shiftapplied
Example:
31+(–21)=10dB
SettingtheDialogueLevelparameterisanessentialservicetothelistener.Foryour
listeners,settingthislevelproperlymeans:
•Thevolumelevelisconsistentwithotherprograms.
•TheDRCprofilesyoumakeavailabletothemworkasyouintend.
Oncedialoguelevelisset,youcan
setupDRCprofilestofurtherbenefittheconsumer.
D.3 Dynamic Range Control
Differenthomelisteningenvironmentspresentawiderangeofrequirementsfordynamic
range.Ratherthansimplycompressingthe audioprogramatthetransmissionsourceto
workwellinthepoorestlisteningenvironments,DolbyDigitalencoderscalculateandsend
DRCmetadatawiththesignal.Thismetadatacanthenbeappliedtothe
signalbythe
decodertoreducethesignal’sdynamicrange.
ThroughthepropersettingofDRCprofilesduring themasteringprocess,thecontent
producercanprovidethebestpossiblepresentationofprogramcontentinvirtuallyany
listeningenvironment,regardlessofthequalityoftheequipment,numberofchannels,or
ambient
noiselevelintheconsumer’shome.
ManyDolbyDigitaldecodersoffertheconsumertheoptionofdefeatingtheDynamic
RangeControlmetadata,butsomedonot.Decoderswithsixdiscretechanneloutputs(full
5.1‐channelcapability)typicallyofferthisoption.Decoderswithstereo,mono,or
RF‐remodulatedoutputs,suchasthose
foundonDVDplayersandset‐topboxes, oftendo
not.Inthesecases,thedecoderautomaticallyappliesthemostappropriateDRCmetadata
forthedecoder’soperatingmode.
Note: The–31dBFSshouldnotbeconfusedwiththestationreferencelevel(often–18or
–20dBFS).Itiscommontohavedifferentvaluesforprogrammaterialthathasthe
samereferencelevel.Anaverageloudnesslevelof–31dBFSisquitecompatible
withfacilitiesrunningatavarietyofreferencelevels.