Dolby Laboratories DP570 Equipment, Output Digital 5.1-Channel Analog 2-Channel, Remodulated, Analog RF

Downmixing

Dolby® DP570 Multichannel Audio Tool User’s Manual 91

Set‐topboxes,usedtoreceiveterrestrial,cable,orsatellitedigitaltelevision,typicallyoffer

ananalogmonosignalmodulatedontheRF/antennaoutput,aline‐levelanalogstereo

signal,andanopticalorcoaxialdigitaloutput.DVDplayersofferananalogstereoanda

digitaloutput,andsomeofferasix‐channelanalogoutput(fora5.1‐channelpresentation).

PortableDVDplayersofferanalogstereo,headphone,anddigitaloutputs.DVDplayersin

computersandgameconsolesofferadigitaloutputaswellasanalogstereo,headphone,

andpossiblysix‐channelanalogoutputs.5.1‐channelamplifiers,decoders,andreceivers

havesix‐channelanalogoutputsandpossiblysixspeaker‐leveloutputs.

Inallofthesecases,aDolbyDigitaldecodercreatestheanalogaudiooutputsignal.

Inthecaseoftheset‐topboxorDVDplayer,theanalogstereooutputisadownmixed

versionoftheDolbyDigitaldatastream.ThedigitaloutputdeliverstheDolbyDigitaldata

streamtoeitheradownstreamdecoderoranintegratedamplifierwithDolbyDigital

decoding.

Ineachofthesedevices,theanalogstereooutputisoneoftwodifferentstereodownmixes.

Onetypeisastereo‐compatibleDolbySurrounddownmix,ofthemultichannelsource

programthatissuitableforDolbySurroundProLogic®decoding.Thiskindofdownmix

isalsocalledProLogicorLefttotal/Righttotal(Lt/Rt).Theothertypeisasimplestereo

representation(calledLeftonly/Rightonly,orLo/Ro)suitableforplaybackonastereohi‐fi

oronheadphones,andfromwhichamonosignalisderivedforuseonanRF/Antenna

output.Thedifferencebetweenthedownmixesishowthesurroundchannelsarehandled.

TheLt/Rtdownmixsumsthesurroundchannelsandaddsthem,in‐phasetotheLeft

channelandout‐of‐phasetotheRightchannel.ThisallowsaDolbySurroundProLogic

decodertoreconstructtheL/C/R/SchannelsforaProLogichometheater.TheLo/Ro

downmixaddstheLeftSurroundandRightSurroundchannelsdiscretelytotheLeftand

Rightspeakerchannels,respectively.Thispreservesthestereoseparationforstereo‐only

monitoringandproducesamono‐compatiblesignal.Inalldownmixes,theLFEchannelis

notincluded.

Onmosthomeequipment,theconsumercanusetheproduct’suserinterfacetochoosethe

appropriatestereooutputforhisplaybacksystem.Themonosignalfeedingthe

RF/antennaoutputisusuallyderivedfromtheLo/Rodownmix.

High‐endDVDplayer × × ×

DVDplayer × ×

PC

Includesgamesconsoles

×(someunits) ×

High‐endset‐topbox

OftenHDTV

×× × ×

Set‐topbox

UsuallySDTV

×××

IDTV

TVsetwithanintegrated

digitalTVtuner

××

High‐endTV

LargescreenTVwitha

5.1‐channelspeakersystem

××

Table D-2 Outputs from Different Equipment Types

EquipmentOutputDigital 5.1-Channel Analog 2-ChannelAnalog RF Remodulated