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,whichcausestheDolbyDigitalencodertoapplya90degree
phaseshifttotheSurroundchannels.ThisallowsaDolbyDigitaldecodertocreateanLt/Rt
downmixsimply.Formostmaterial,thephaseshifthasaminimalimpactwhentheDolby
Digitalprogramisdecodedto5.1channels,butitprovidesanLt/Rtoutputthatcanbe
decodedwithProLogictoL,C,R,andS,ifdesired.
Otherwise,werecommendthatyouleavethisparameterenabledfornormalprogram
materialtoavoidproblemswiththeanalogoutputsofsettopboxes.
D.7 Extended Bitstream Information Parameters
Inresponsetorequestsfromcontentproducers,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