计算机英语Sound card.docx
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计算机英语Sound card.docx
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计算机英语Soundcard
Soundcard
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SoundCard
ASoundBlasterLive!
Valuecard,atypical(circa2000)PCIsoundcard.
Connectsto
Motherboard via oneof:
∙PCI
∙ISA
∙USB
∙IEEE1394
∙IBMPCParallelPort
∙PCI-E
∙MCA(rare)
∙PCMCIAinterfaces(PCCard,Expresscard)
Lineinorout:
via oneof:
∙Analogue-TRS,RCAorDINconnector
∙Digital-RCA,TOSLinkorAES/EBU
Microphone via oneof:
∙TRSconnector
∙PINconnector
Commonmanufacturers
CreativeLabs(andsubsidiaryE-muSystems)
Realtek
C-Media
M-Audio
TurtleBeach
Asoundcard(alsoknownasanaudiocard)isaninternalcomputerexpansioncardthatfacilitatestheinputandoutputofaudiosignalstoandfromacomputerundercontrolofcomputerprograms.
Confusingly,thetermsoundcardisalsoappliedtoexternalaudiointerfacesthatusesoftwaretogeneratesound,asopposedtousinghardwareinsidethePC.Thesesoftware-baseddevicesarebetterknownasaudiointerfaces.
Typicalusesofsoundcardsincludeprovidingtheaudiocomponentformultimediaapplicationssuchasmusiccomposition,editingvideooraudio,presentation,education,andentertainment(games)andvideoprojection.Manycomputershavesoundcapabilitiesbuiltin,whileothersrequireadditionalexpansioncardstoprovideforaudiocapability.
Contents
[hide]
∙1Generalcharacteristics
o1.1Soundchannelsandpolyphony
∙2Colorcodes
∙3HistoryofsoundcardsfortheIBMPCarchitecture
o3.1Hardwaremanufacturers
o3.2Industryadoption
o3.3Featureevolution
▪3.3.1Cripplingoffeatures
o3.4Professionalsoundcards(audiointerfaces)
∙4Sounddevicesotherthanexpansioncards
o4.1IntegratedsoundhardwareonPCmotherboards
o4.2Integratedsoundonotherplatforms
o4.3Soundcardsonotherplatforms
o4.4USBsound"cards"
o4.5Otheroutboardsounddevices
∙5Driverarchitecture
∙6Seealso
∙7References
∙8Externallinks
[edit]Generalcharacteristics
Close-upofasoundcardPCB,showingelectrolyticcapacitors,SMTcapacitorsandresistors,andaYAC512two-channel16-bitDAC.
Soundcardsusuallyfeatureadigital-to-analogconverter(DAC),whichconvertsrecordedorgenerateddigitaldataintoananalogformat.Theoutputsignalisconnectedtoanamplifier,headphones,orexternaldeviceusingstandardinterconnects,suchasaTRSconnectororanRCAconnector.Ifthenumberandsizeofconnectorsistoolargeforthespaceonthebackplatetheconnectorswillbeoff-board,typicallyusingabreakoutbox,oranauxiliarybackplate.Moreadvancedcardsusuallyincludemorethanonesoundchiptoprovideforhigherdataratesandmultiplesimultaneousfunctionality,forexampledigitalproductionofsynthesizedsounds(usuallyforreal-timegenerationofmusicandsoundeffectsusingminimaldataandCPUtime).
DigitalsoundreproductionisusuallydonewithmultichannelDACs,whicharecapableofsimultaneousdigitalsamplesatdifferentpitchesandvolumesandapplicationofreal-timeeffects,likefilteringordistortion.Multichanneldigitalsoundplaybackcanalsobeusedformusicsynthesis,whenusedwithacompliance[clarificationneeded],andevenmultiple-channelemulation.Thisapproachhasbecomecommonasmanufacturersseeksimplerandlower-costsoundcards.
Mostsoundcardshavealineinconnectorforaninputsignalfromacassettetapeorothersoundsourcethathashighervoltagelevelsthanamicrophone.Thesoundcarddigitizesthissignalandstoresit(undercontrolofappropriatematchingcomputersoftware)onthecomputer'sharddiskforstorage,editing,orfurtherprocessing.Anothercommonexternalconnectoristhemicrophoneconnector,forsignalsfromamicrophoneorotherlow-levelinputdevice.Inputthroughamicrophonejackcanbeused,forexample,byspeechrecognitionorvoiceoverIPapplications.
[edit]Soundchannelsandpolyphony
8-channelDACCirrusLogicCS4382placedonSoundBlasterX-FiFatal1ty.
Animportantsoundcardcharacteristicispolyphony,whichreferstoitsabilitytoprocessandoutputmultipleindependentvoicesorsoundssimultaneously.Thesedistinctchannelsareseenasthenumberofaudiooutputs,whichmaycorrespondtoaspeakerconfigurationsuchas2.0(stereo),2.1(stereoandsubwoofer),5.1(surround),orotherconfiguration.Sometimes,thetermsvoiceandchannelareusedinterchangeablytoindicatethedegreeofpolyphony,nottheoutputspeakerconfiguration.
Forexample,manyoldersoundchipscouldaccommodatethreevoices,butonlyoneaudiochannel(ie,asinglemonooutput)foroutput,requiringallvoicestobemixedtogether.Latercards,suchastheAdLibsoundcard,hada9-voicepolyphonycombinedin1monooutputchannel.
Forsomeyears,mostPCsoundcardshavehadmultipleFMsynthesisvoices(typically9or16)whichwereusuallyusedforMIDImusic.Thefullcapabilitiesofadvancedcardsaren'toftencompletelyused;onlyone(mono)ortwo(stereo)voice(s)andchannel(s)areusuallydedicatedtoplaybackofdigitalsoundsamples,andplayingbackmorethanonedigitalsoundsampleusuallyrequiresasoftwaredownmixatafixedsamplingrate.Modernlow-costintegratedsoundcards(ie,thosebuiltintomotherboards)suchasaudiocodecslikethosemeetingtheAC'97standardandevensomelower-costexpansionsoundcardsstillworkthisway.Thesedevicesmayprovidemorethantwosoundoutputchannels(typically5.1or7.1surroundsound),buttheyusuallyhavenoactualhardwarepolyphonyforeithersoundeffectsorMIDIreproduction–thesetasksareperformedentirelyinsoftware.Thisissimilartothewayinexpensivesoftmodemsperformmodemtasksinsoftwareratherthaninhardware.
Also,intheearlydaysofwavetablesynthesis,somesoundcardmanufacturersadvertisedpolyphonysolelyontheMIDIcapabilitiesalone.Inthiscase,thecard'soutputchannelisirrelevant(andtypically,thecardisonlycapableoftwochannelsofdigitalsound).Instead,thepolyphonymeasurementsolelyappliestotheamountofMIDIinstrumentsthesoundcardiscapableofproducingatonegiventime.
Today,asoundcardprovidingactualhardwarepolyphony,regardlessofthenumberofoutputchannels,istypicallyreferredtoasa"hardwareaudioaccelerator",althoughactualvoicepolyphonyisnotthesole(orevenanecessary)prerequisite,withotheraspectssuchashardwareaccelerationof3Dsound,positionalaudioandreal-timeDSPeffectsbeingmoreimportant.
Sincedigitalsoundplaybackhasbecomeavailableandprovidedbetterperformancethansynthesis,modernsoundcardswithhardwarepolyphonydon'tactuallyuseDACswithasmanychannelsasvoices.Instead,theyperformvoicemixingandeffectsprocessinginhardware(eventuallyperformingdigitalfilteringandconversionstoandfromthefrequencydomainforapplyingcertaineffects)insideadedicatedDSP.Thefinalplaybackstageisperformedbyanexternal(inreferencetotheDSPchip(s))DACwithsignificantlyfewerchannelsthanvoices(e.g.,8channelsfor7.1audio,whichcanbedividedamong32,64oreven128voices).
[edit]Colorcodes
ConnectorsonthesoundcardsarecolourcodedasperthePCSystemDesignGuide.Theywillalsohavesymbolswitharrows,holesandsoundwavesthatareassociatedwitheachjackposition,themeaningofeachisgivenbelow:
Colour
Function
Connector
symbol
Pink
Analogmicrophoneaudioinput.
3.5 mmTRS
Amicrophone
Lightblue
Analoglinelevelaudioinput.
3.5 mmTRS
Anarrowgoingintoacircle
Limegreen
Analoglinelevelaudiooutputforthemainstereosignal(frontspeakersorheadphones).
3.5 mmTRS
Arrowgoingoutonesideofacircleintoawave
Brown/Dark
Analoglinelevelaudiooutputforaspecialpanning,'Right-to-leftspeaker'.
3.5 mmTRS
Black
Analoglinelevelaudiooutputforsurroundspeakers,typicallyrearstereo.
3.5 mmTRS
Orange
Analoglinelevelaudiooutputforcenterchannelspeakerandsubwoofer
3.5 mmTRS
Gold/Grey
Gameport/MIDI
15pinD
Arrowgoingoutbothsidesintowaves
[edit]HistoryofsoundcardsfortheIBMPCarchitecture
TheAdLibMusicSynthesizerCard,wasoneofthefirstsoundcardscirca1990.Notethemanualvolumeadjustmentknob.
ATurtleBeachsoundcard
EchoDigitalAudio'sIndigoIO—PCMCIAcard24-bit96kHzstereoin/outsoundcard.
SoundcardsforcomputerscompatiblewiththeIBMPCwereveryuncommonuntil1988,whichleftthesingleinternalPCspeakerastheonlywayearlyPCsoftwarecouldproducesoundandmusic.Thespeakerhardwarewastypicallylimitedtosquarewaves,whichfitthecommonnicknameof"beeper".Theresultingsoundwasgenerallydescribedas"beepsandboops".Severalcompanies,mostnotablyAccessSoftware,developedtechniquesfordigitalsoundreproductionoverthePCspeaker;theresultingaudio,whilebaldlyfunctional,sufferedfromdistortedoutputandlowvolume,andusuallyrequiredallotherprocessingtobestoppedwhilesoundswereplayed.Otherhomecomputermodelsofthe1980sincludedhardwaresupportfordigitalsoundplayback,ormusicsynthesis(orboth),leavingtheIBMPCatadisadvantagetothemwhenitcametomultimediaapplicationssuchasmusiccompositionorgaming.
ItisimportanttonotethattheinitialdesignandmarketingfocusesofsoundcardsfortheIBMPCplatformwerenotbasedongaming,butratheronspecificaudioapplicationssuchasmusiccomposition(AdLibPersonalMusicSystem,CreativeMusicSystem,IBMMusicFeatureCard)oronspeechsynthesis(DigispeechDS201,CovoxSpeechThing,StreetElectronicsEcho).NotuntilSierraandothergamecompaniesbecameinvolvedin1988w
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