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Dolby Laboratories DP570 Stereo System User Manual

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DP570 Multichannel Audio Tool User’s Manual

A Guide to Dolby Metadata Dynamic Range Control

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

DynamicRangeControl(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.

TheDolbyDigitalstreamcarriesmetadataforthetwopossibleoperatingmodesinthe

decoder.Theoperatingmodesareknown

asLinemodeandRFmodeduetothetypeof

outputtheyaretypicallyassociatedwith.Linemodeistypicallyusedondecoderswithsix‐

ortwo‐channelline‐leveloutputsandRFmodeisusedondecodersthathavean

RF‐remodulatedoutput.Full‐featureddecodersallowtheconsumer

toselectwhetherto

useDRCandifso,whichoperatingmodetouse.TheconsumerseesoptionssuchasOff,

LightCompression,andHeavyCompressioninsteadofNone,Linemode,andRFmode.

Advanceddecodersmayalsoallowcustomscalingofthe DRCmetadata.

Allthatneedstobedone

duringmetadataauthoring,orencoding,isselectionofthe

dynamicrangecontrolprofilesforLinemodeandRFmode.Theprofilesaredescribedin

thefollowingsections.

Line Mode

Linemodeoffersthesefeatures:

•Low‐levelsignalboostcompressionscalingisallowed.

•High‐levelsignalcutcompressionscalingisallowedwhennotdownmixing.

•Thenormalizeddialoguelevelisreproducedfromthedecoderataconstantloudness

levelof–31dBFSLeq(A),assumingtheDialogueLevelparameterissetcorrectly.

Line‐level

orpower‐amplifiedoutputsfromtwo‐channelset‐topdecoders,two‐channel

digitaltelevisions,5.1‐channeldigitaltelevisions,DolbyDigitalA/Vsurrounddecoders,

andoutboardDolbyDigitaladaptersuseLinemode.

Consumercontrolofthedynamicrangeislimitedwhendownmixing.Productswithstereo

ormonooutputsdonot usuallyallow

consumerscalingofLinemode.Thisisbecausethese

Note:WhiletheuseofDRCmodesduringdecodingisaconsumer‐selectablefeature,the

DialogueLevelparametersettingisnot.Therefore,settingtheDialogueLevel

parameterproperlyisessentialbeforepreviewingaDRCprofile.

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