- Dolby Multichannel Audio Tool User's Manual

Downmixing
Dolby
®
DP570 Multichannel Audio Tool User’s Manual 91
Settopboxes,usedtoreceiveterrestrial,cable,orsatellitedigitaltelevision,typicallyoffer
ananalogmonosignalmodulatedontheRF/antennaoutput, alinelevelanalogstereo
signal,andanopticalorcoaxialdigitaloutput.DVDplayersofferananalogstereoanda
digitaloutput,andsomeoffer
asixchannelanalogoutput(fora5.1channelpresentation).
PortableDVDplayersofferanalogstereo,headphone,anddigitaloutputs.DVDplayersin
computersandgameconsolesofferadigitaloutputaswellasanalogstereo,headphone,
andpossiblysixchannelanalogoutputs.5.1channelamplifiers,decoders,andreceivers
havesix
channelanalogoutputsandpossiblysixspeakerleveloutputs.
Inallofthesecases,aDolbyDigitaldecodercreatestheanalogaudiooutputsignal.
InthecaseofthesettopboxorDVD player,theanalogstereooutputisadownmixed
versionoftheDolbyDigitaldatastream.Thedigital
outputdeliverstheDolbyDigitaldata
streamtoeitheradownstreamdecoderoranintegratedamplifierwithDolbyDigital
decoding.
Ineachofthesedevices,theanalogstereooutputisoneoftwodifferentstereodownmixes.
OnetypeisastereocompatibleDolbySurrounddownmix,ofthemultichannelsource
programthat
issuitableforDolbySurroundProLogic
®
decoding.Thiskindofdownmix
isalsocalledProLogicorLefttotal/Righttotal(Lt/Rt).Theothertypeisasimplestereo
representation(calledLeftonly/Rightonly,orLo/Ro)suitableforplaybackonastereohifi
oronheadphones,andfromwhichamonosignalisderivedforuse
onanRF/Antenna
output.Thedifferencebetweenthedownmixesishowthesurroundchannelsarehandled.
TheLt/Rtdownmixsumsthesurroundchannelsandaddsthem,inphasetotheLeft
channelandoutofphasetotheRightchannel.ThisallowsaDolbySurroundProLogic
decodertoreconstructthe
L/C/R/SchannelsforaProLogichometheater.TheLo/Ro
downmixaddstheLeftSurroundandRightSurroundchannelsdiscretelytotheLeftand
Rightspeakerchannels,respectively.Thispreservesthestereoseparationforstereoonly
monitoringandproducesamonocompatiblesignal.Inalldownmixes,theLFEchannelis
notincluded.
Onmosthomeequipment,theconsumercanusetheproduct’suserinterfacetochoosethe
appropriatestereooutputforhisplaybacksystem.Themonosignalfeedingthe
RF/antennaoutputisusuallyderivedfromtheLo/Rodownmix.
HighendDVDplayer × × ×
DVDplayer × ×
PC
Includesgamesconsoles
×(someunits) ×
Highendsettopbox
OftenHDTV
×× × ×
Settopbox
UsuallySDTV
×××
IDTV
TVsetwithanintegrated
digitalTVtuner
××
HighendTV
LargescreenTVwitha
5.1channelspeakersystem
××
Table D-2 Outputs from Different Equipment Types
Equipment
Output
Digital
5.1-Channel
Analog
2-Channel
Analog
RF
Remodulated