
Extended Bitstream Information Parameters
Dolby® DP570 Multichannel Audio Tool User’s Manual 99
frequenciesabove120Hzthatwouldcausealiasingwhendecoded.Thisfiltershouldonly
beswitchedoffiftheaudiotobeencodedisknowntohavenosignalabove120Hz.
Surround 3 dB Attenuation
TheSurround3dBAttenuationparameterdetermineswhetherthesurroundchannel(s)
areattenuated3dBbeforeencoding.TheattenuationactuallytakesplaceinsidetheDolby
Digitalencoder.Itbalancesthesignallevelsbetweentheatricalmixingrooms(dubbing
stages)andconsumermixingrooms(DVDorTVstudios).Consumermixingroomsare
calibratedsothatallfivemainchannelsareatthesamesoundpressurelevel(SPL).To
maintaincompatibilitywitholderfilmformats,theatricalmixingroomscalibratetheSPL
ofthesurroundchannels3dBlowerthanthefrontchannels.Theconsequenceisthatsignal
levelsontapeare3dBlouder.Therefore,toconvertfromatheatricalcalibrationtoa
consumermix,itisnecessarytoreducethesurroundlevelsby3dBbyenablingthis
parameter.
Surround Phase Shift
ThedefaultsettingisEnabled,whichcausestheDolbyDigitalencodertoapplya90‐degree
phaseshifttotheSurroundchannels.ThisallowsaDolbyDigitaldecodertocreateanLt/Rt
downmixsimply.Formostmaterial,thephaseshifthasaminimalimpactwhentheDolby
Digitalprogramisdecodedto5.1channels,butitprovidesanLt/Rtoutputthatcanbe
decodedwithProLogictoL,C,R,andS,ifdesired.
Otherwise,werecommendthatyouleavethisparameterenabledfornormalprogram
materialtoavoidproblemswiththeanalogoutputsofset‐topboxes.
D.7 Extended Bitstream Information ParametersInresponsetorequestsfromcontentproducers,DolbyLaboratoriesmodifiedthe
definitionsofseveralmetadataparametersfromtheiroriginaldefinitionasdescribedin
Table D-18 LFE Lowpass Filter Settings
LFE Lowpass Filter
Enabled
Disabled
Table D-19 Surround 3 dB Attenuation Settings
Surround 3 dB
Attenuation
Enabled
Disabled
Note: Thisparametershouldalwaysbeturnedoffwhenyouareworkingwithsteady
statetonesfortestingpurposes(forexamplecalibrationdiscs).
Table D-20 Surround Phase Shift Settings
Surround Phase Shift
Enabled
Disabled