- Dolby Multichannel Audio Tool User's Manual
Downmixing
Dolby
®
DP570 Multichannel Audio Tool User’s Manual 91
Set‐topboxes,usedtoreceiveterrestrial,cable,orsatellitedigitaltelevision,typicallyoffer
ananalogmonosignalmodulatedontheRF/antennaoutput, aline‐levelanalogstereo
signal,andanopticalorcoaxialdigitaloutput.DVDplayersofferananalogstereoanda
digitaloutput,andsomeoffer
asix‐channelanalogoutput(fora5.1‐channelpresentation).
PortableDVDplayersofferanalogstereo,headphone,anddigitaloutputs.DVDplayersin
computersandgameconsolesofferadigitaloutputaswellasanalogstereo,headphone,
andpossiblysix‐channelanalogoutputs.5.1‐channelamplifiers,decoders,andreceivers
havesix
‐channelanalogoutputsandpossiblysixspeaker‐leveloutputs.
Inallofthesecases,aDolbyDigitaldecodercreatestheanalogaudiooutputsignal.
Inthecaseoftheset‐topboxorDVD player,theanalogstereooutputisadownmixed
versionoftheDolbyDigitaldatastream.Thedigital
outputdeliverstheDolbyDigitaldata
streamtoeitheradownstreamdecoderoranintegratedamplifierwithDolbyDigital
decoding.
Ineachofthesedevices,theanalogstereooutputisoneoftwodifferentstereodownmixes.
Onetypeisastereo‐compatibleDolbySurrounddownmix,ofthemultichannelsource
programthat
issuitableforDolbySurroundProLogic
®
decoding.Thiskindofdownmix
isalsocalledProLogicorLefttotal/Righttotal(Lt/Rt).Theothertypeisasimplestereo
representation(calledLeftonly/Rightonly,orLo/Ro)suitableforplaybackonastereohi‐fi
oronheadphones,andfromwhichamonosignalisderivedforuse
onanRF/Antenna
output.Thedifferencebetweenthedownmixesishowthesurroundchannelsarehandled.
TheLt/Rtdownmixsumsthesurroundchannelsandaddsthem,in‐phasetotheLeft
channelandout‐of‐phasetotheRightchannel.ThisallowsaDolbySurroundProLogic
decodertoreconstructthe
L/C/R/SchannelsforaProLogichometheater.TheLo/Ro
downmixaddstheLeftSurroundandRightSurroundchannelsdiscretelytotheLeftand
Rightspeakerchannels,respectively.Thispreservesthestereoseparationforstereo‐only
monitoringandproducesamono‐compatiblesignal.Inalldownmixes,theLFEchannelis
notincluded.
Onmosthomeequipment,theconsumercanusetheproduct’suserinterfacetochoosethe
appropriatestereooutputforhisplaybacksystem.Themonosignalfeedingthe
RF/antennaoutputisusuallyderivedfromtheLo/Rodownmix.
High‐endDVDplayer × × ×
DVDplayer × ×
PC
Includesgamesconsoles
×(someunits) ×
High‐endset‐topbox
OftenHDTV
×× × ×
Set‐topbox
UsuallySDTV
×××
IDTV
TVsetwithanintegrated
digitalTVtuner
××
High‐endTV
LargescreenTVwitha
5.1‐channelspeakersystem
××
Table D-2 Outputs from Different Equipment Types
Equipment
Output
Digital
5.1-Channel
Analog
2-Channel
Analog
RF
Remodulated