Dolby Laboratories DP570 LFE Lowpass Filter , Surround 3 dB Attenuation , Surround Phase Shift

100 Dolby® DP570 Multichannel Audio Tool User’s Manual

A Guide to Dolby Metadata Parameter Definitions

itpreventsaliasingondecodingandisnormallyswitchedon.Thisparameterisnotpassed

totheconsumerdecoder.

LFE Lowpass Filter

Thisparameterdetermineswhethera120Hzeighth‐orderlowpassfilterisappliedtothe

LFEchannelinputofaDolbyDigitalencoderpriortoencoding.ItisignorediftheLFE

channelisdisabled.Thisparameterisnotsenttotheconsumerdecoder.Thefilterremoves

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.

Surround 3 dB Attenuation

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.

Surround Phase Shift

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

Table D-17 Lowpass Filter Setting

Enabled

Disabled

Table D-18 LFE Lowpass Filters

Enabled

Disabled

Table D-19 Surround 3 dB Attenuation Settings

Enabled

Disabled