Dynamic Range Control
Dolby® DP570 Multichannel Audio Tool User’s Manual 87
DolbyDigitalconsumerdecodersnormalizetheaverageoutputlevel—thatis,theoutput
levelaveragedovertime—to–31dBFS(31dBbelow0dBfullscaledigitaloutput)by
applyingashiftinlevelbasedontheDialogueLevelparametersetting.
Whenadecoderreceivesaninputsignalwithadialoguelevelof–31,itappliesnolevel
shifttothesignalbecausethisindicatestothedecoderthatthesignalalreadymatchesthe
targetlevelandthereforerequiresnoshift.Incontrast,alouderprogramrequiresashiftto
matchthe–31dBstandard.Whenthedialoguelevelparametersettingis–21,thedecoder
appliesa10dBlevelshifttothesignal.Whenthesettingis–11,itappliesa20dBlevelshift,
andsoon.

A Simple Rule:

31+(DialogueLevelvalue)=Shiftapplied

Example:

31+(–21)=10dB
SettingtheDialogueLevelparameterisanessentialservicetothelistener.Foryour
listeners,settingthislevelproperlymeans:
•Thevolumelevelisconsistentwithotherprograms.
•TheDRCprofilesyoumakeavailabletothemworkasyouintend.
Oncedialoguelevelisset,youcansetupDRCprofilestofurtherbenefittheconsumer.
D.3 Dynamic Range Control
Differenthomelisteningenvironmentspresentawiderangeofrequirementsfordynamic
range.Ratherthansimplycompressingtheaudioprogramatthetransmissionsourceto
workwellinthepoorestlisteningenvironments,DolbyDigitalencoderscalculateandsend
DRCmetadatawiththesignal.Thismetadatacanthenbeappliedtothesignalbythe
decodertoreducethesignal’sdynamicrange.
ThroughthepropersettingofDRCprofilesduringthemasteringprocess,thecontent
producercanprovidethebestpossiblepresentationofprogramcontentinvirtuallyany
listeningenvironment,regardlessofthequalityoftheequipment,numberofchannels,or
ambientnoiselevelintheconsumer’shome.
ManyDolbyDigitaldecodersoffertheconsumertheoptionofdefeatingtheDynamic
RangeControlmetadata,butsomedonot.Decoderswithsixdiscretechanneloutputs(full
5.1channelcapability)typicallyofferthisoption.Decoderswithstereo,mono,or
RFremodulatedoutputs,suchasthosefoundonDVDplayersandsettopboxes,oftendo
not.Inthesecases,thedecoderautomaticallyappliesthemostappropriateDRCmetadata
forthedecoder’soperatingmode.
Note: The–31dBFSshouldnotbeconfusedwiththestationreferencelevel(often–18or
–20dBFS).Itiscommontohavedifferentvaluesforprogrammaterialthathasthe
samereferencelevel.Anaverageloudnesslevelof–31dBFSisquitecompatible
withfacilitiesrunningatavarietyofreferencelevels.