Dolby Laboratories DP570 D.7 Extended Bitstream Information Parameters

Extended Bitstream Information Parameters

Dolby® DP570 Multichannel Audio Tool User’s Manual 99

frequenciesabove120Hzthatwouldcausealiasingwhendecoded.Thisfiltershouldonly

beswitchedoffiftheaudiotobeencodedisknowntohavenosignalabove120Hz.

TheSurround3dBAttenuationparameterdetermineswhetherthesurroundchannel(s)

areattenuated3dBbeforeencoding.TheattenuationactuallytakesplaceinsidetheDolby

Digitalencoder.Itbalancesthesignallevelsbetweentheatricalmixingrooms(dubbing

stages)andconsumermixingrooms(DVDorTVstudios).Consumermixingroomsare

calibratedsothatallfivemainchannelsareatthesamesoundpressurelevel(SPL).To

maintaincompatibilitywitholderfilmformats,theatricalmixingroomscalibratetheSPL

ofthesurroundchannels3dBlowerthanthefrontchannels.Theconsequenceisthatsignal

levelsontapeare3dBlouder.Therefore,toconvertfromatheatricalcalibrationtoa

consumermix,itisnecessarytoreducethesurroundlevelsby3dBbyenablingthis

parameter.

ThedefaultsettingisEnabled,whichcausestheDolbyDigitalencodertoapplya90‐degree

phaseshifttotheSurroundchannels.ThisallowsaDolbyDigitaldecodertocreateanLt/Rt

downmixsimply.Formostmaterial,thephaseshifthasaminimalimpactwhentheDolby

Digitalprogramisdecodedto5.1channels,butitprovidesanLt/Rtoutputthatcanbe

decodedwithProLogictoL,C,R,andS,ifdesired.

Otherwise,werecommendthatyouleavethisparameterenabledfornormalprogram

materialtoavoidproblemswiththeanalogoutputsofset‐topboxes.

D.7 Extended Bitstream Information Parameters

Inresponsetorequestsfromcontentproducers,DolbyLaboratoriesmodifiedthe

definitionsofseveralmetadataparametersfromtheiroriginaldefinitionasdescribedin

Table D-18 LFE Lowpass Filter Settings

Enabled

Disabled

Table D-19 Surround 3 dB Attenuation Settings

Enabled

Disabled

Note: Thisparametershouldalwaysbeturnedoffwhenyouareworkingwithsteady

statetonesfortestingpurposes(forexamplecalibrationdiscs).

Table D-20 Surround Phase Shift Settings

Enabled

Disabled