Dolby Laboratories DP570 D.2 Dialogue Level

86 Dolby® DP570 Multichannel Audio Tool User’s Manual

A Guide to Dolby Metadata

ThereareprofessionalparametersintheDolbyEbitstreamthatarenotunderdirectuser

control,suchasTimecodeandPitchShift.

DolbyEbitstreamscarrytimecodeinformationinhours:minutes:seconds:framesformat.

ThePitchShiftparametercanbegeneratedautomaticallybyaDolbyEdecodertocontrol

theDolbyModel585TimeScalingProcessor.IftheinputtotheDolbyEdecoderisnotat

normalplayspeed(aswithvarispeedorprogramplay),thenthePitchShiftCode

parameterindicatestheamountofaudiopitchshiftingrequiredtorestoretheoriginal

programpitch.

D.2 Dialogue Level

DialogueLevelisperhapsthesinglemostimportantmetadataparameter.TheDialogue

LevelSetvaluerepresentsthelong‐termlevelofdialoguewithinapresentation,measured

accordingtoITU‐RRec.BS.1770.ThislevelcanbequantifiedwiththeDolbyLM100

BroadcastLoudnessMeter.

Whenreceivedattheconsumer’sDolbyDigitaldecoder,thisparametersettingdetermines

alevelshiftinthedecoderthatsets,ornormalizes,theaverageaudiooutputofthedecoder

toapresetlevel.Thisaidsinmatchingaudiovolumebetweenprogramsources.

Inbroadcasttransmission,thepropersettingofDialogueLevelensuresthattheconsumer

receivesastandardlisteninglevel,soswitchingchannelsorwatchingatelevisionprogram

throughthecommercialbreaksdoesn’trequireadjustingthevolume.Usingthesame

standardforallcontent,whetherconveyed��bybroadcasttelevision,DVD,orothermedia,

enablestheconsumertoswitchbetweensourcesandprogramswhilemaintaininga

comfortableandconsistentlisteninglevel.

ThepropersettingoftheDialogueLevelparameteralsoenablestheDynamicRange

Controlprofileschosenbythecontentproducertoworkasintendedinless‐than‐optimal

listeningenvironments,andisessentialinanycontentproduction,whetheritisfor

transmissioninabroadcaststreamorfordirectdistributiontoconsumers,aswithDVDs.

ThescaleusedintheDialogueLevelsettingrangesin1dBstepsfrom–1to–31dB.

Contrarytowhatyoumightassumeatfirst,asettingof–31representsnolevelshiftinthe

consumer’sdecoder,and–1representsthemaximumlevelshift.Here’swhy:

Note: Programswithoutdialogue,suchasanall‐musicprogram,stillrequireacareful

settingoftheDialogueLevelparameter.Whensettingtheparameterforsuch

content,itisusefultocomparetheprogramtothelevelofotherprograms.Thegoal

istoallowtheconsumertoswitchtoyourprogramwithouthavingtoadjustthe

volumecontrol.