Using IP for Broadcast Studio Audio
•‹‰ˆ‘””‘ƒ†…ƒ•––—†‹‘—†‹‘
SkipPizzi
ExecutiveSummary
Arevolutioniscurrentlytakingplaceinthefieldofaudiostudiodesign.Itinvolvesafundamental
rethinkingofthewaysignalsaredistributedandmanagedthroughoutthebroadcastfacility.
AnewapproachtothisprocessutilizesadigitaltransmissionformatsimilartothatusedontheInternet
forpurposesoftransportanddistributionofcontentaroundanaudioproductionenvironment.
ThisformatisknownastheInternetProtocol,generallyreferredtoas“IP,”anditistheverycoreofthe
Internet.IPisthecommonformatusedforanykindofdatathatflowsontheInternet(including
streamingmedia),andonprivateextensionsoftheInternet,suchastheLANsemployedinenterprise
networksandsmalloffice/homeoffice(SOHO)networks,bothwiredandwireless.Itsetstherulesfor
thisentiredatanetworkinginfrastructure,bothhardwareandsoftware,whichhasemergedandbeen
sobroadlyembracedoverthelastquartercenturyormore.Sincemostaudiofacilitieshavealready
convertedtodigitalaudio,itthereforemakessensetonowexaminetheuseofIPthere,aswell.
GiventhatIPisthelinguafrancaofcontemporarydatanetworking,itcanprovidesignificanteconomies
ofscaleforspecializedapplicationssuchasprofessionaldigitalaudiodistribution.Thisexploitsthesame
processthathasmadethegeneralͲpurposedesktopcomputeranefficientandcostͲeffectiveplatform
forthecreationandstorageofprofessionalaudiocontent.IPAudiodistributionissimplyanextension
ofthatthinkingandtechnology,replacingthepurposeͲbuilt(andrelativelyexpensive)mixers,routers
andswitchersthathavetraditionallybeenusedbyaudiostudiosformanagingmultipleaudiosignalsas
theypassthroughaproductionorbroadcastfacility.IPalsoallowsthefullandcontinuingforceof
Moore’sLawtobeappliedtoaudiodistribution,justasthePChasdoneforotheraudioprocesses.
BeyondsimplecostͲeffectiveness,however,IPAudiooffersotherimportantbenefits.Theseincludehigh
scalability(i.e.,theabilitytoeasilyaccommodategrowthandotherconfigurationchanges),convenience
(i.e.,easyandfastinstallation)and“futureͲproofing”(i.e.,highlikelihoodoffittingwellintoanyscenario
forfuturefacilityrequirements).Puttingalltheseelementstogethercreatesavaluepropositionthatis
hardtoignorewhenconsideringoptionsfornewfacilitydesignsorexistingstudioupgrades.
ManyotherindustrieshavealreadyconvertedtheirlegacycommunicationsprocessestoIPͲbased
replacementsystems.StudioaudiosystemsusingIPͲbasedtechnologyarenowsufficientlymatureto
allowaudioproducersandbroadcasterstodothesame,providingthemwithsubstantialsavingswhile
simultaneouslypositioningthemwelltoaccommodateindeterminatefutureneeds.
UsingIPforBroadcastStudioAudio
ƒ‰‡ͳ
Introduction
Thispaperconsidersthereplacementoftraditionalformsofaudiosignaltransportinthebroadcast
studiowithnetworkedaudiocarriedviaInternetProtocol(IP).Itexaminesthevalueandprocessofsuch
conversion,thechallengestodoingso,andthelikelyfutureofthisenvironment.
ThisstudywascommissionedbyAxiaAudioinearly2008.
ABriefHistory
Thebroadcastaudiostudiohasalonglegacyrelationshipwiththetelecommunicationsworld.The
earliestaudiofacilitiesandstandardpracticesweredevelopedbyBellSystemandWesternElectric
engineersintheearly20thcentury,andthetwoworldshaveneverstrayedfarfromeachothersince.
Inparticular,broadcastaudiohasretainedacloseconnectiontothetelecomenvironment,sinceso
muchofbroadcasting’scontentcomesand/orgoesfromthestudioviatelcoͲprovidedpaths.
Thusitisnotsurprisingthatthenextgenerationofstudioaudiotechnologyshouldonceagainfollowa
pathblazedbytelecommunicationstechnologies.
Inthiscase,thetechnologyinvolvesdigitalnetworking–specificallyusingthepopularandnownearly
ubiquitousInternetProtocol(IP).Thisprotocol,coupledwitheithertheTransmissionControlProtocol
(TCP)orUniversalDatagramProtocol(UDP)datatransportformat,providesthebulkofdata
communicationcarriedontheInternet.Itspopularityforthatpurposehasalsomadeitusefulforother
localized,nonͲInternetdatanetworkingpurposes.Thisisprimarilyduetothevolumeofdevelopment
andresultinghardwareandsoftwarethatsupportsTCP/IPorUDP/IP,andthegreateconomyofscale
thatresults.
Foralittlebackground,notethata“protocol”inthedatanetworkingcontextissimplyanagreementon
theformatofdatathatwillbepassedbetweendevices.Thereforeitspecifiesasetofrulesforvarious
parametersofthatdata,suchasthedataratesallowed,theerrorcheckingalgorithmsemployed,any
datacompressionformatsthatmightbeused,howthestartandendofindividualmessageswillbe
determined,howconfirmationthatamessagehasbeensuccessfullydeliveredwillbecommunicated,
andsoon.
It’salsohelpfultoreviewsomeoftheearlydevelopmentthatledtoIP’sparticularpopularity.Ina
nutshell,theIPapproachisasimplificationofthecanonicalsevenͲlayernetworkingarchitecture 1 down
toastackconsistingofonlyfourlayers,asshowninTable1.
1
TheOpenSystemsInterconnection(OSI)referencemodel,establishedinthelate1970s,includedApplication,
Presentation,Session,Transport,Network,DataLink,andPhysicallayers.
UsingIPforBroadcastStudioAudio
ƒ‰‡ʹ
APPLICATION
TRANSPORT
NETWORK
LINK
HTTP,RTP,FTP,SMTP,TELNET
TCP,UDP
IP
Ethernet,WiFi
Table1:ThefourlayersofInternetdatatransmission,withsomeexamplesofeachlayer’sprotocols.
TheInternetprocessalsoincludesanaddressingprotocolforeachofitsdatapackets,theIPaddress.
AnydeviceattachedtoanIPnetworkisassignedanIPaddress.Untilrecently–i.e.,usingIPv4–anIP
addresswasspecifiedasanumericstringoffouroneͲbytenumbers(oroctets,sinceonebyteiseight
bits),eachexpressedindecimalform(from0to255)andseparatedbyperiods(e.g.,169.10.206.2).2 ThisimpliesthatthenumberofpossibleaddressesinIPv4isthatexpressedbya32Ͳbitnumber(4x8
bits),meaningthat232,orapproximately4.3billion(4.3x109),uniqueIPaddressesareavailable.This
maysoundlikealot,butmanyofthesearereservedforspecificuses(moreonthisbelow).
Today,theIPworldisconvertingtoIPv6,whichspecifiesitsIPaddressesusing128Ͳbitratherthan32Ͳbit
numbers.3 ThenumericalexpressionofIPv6addressesalsodiffersfromIPv4’s,inthatitgenerallyuses
hexadecimalnumbersintheformhhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh,whereeachbyte(or
octet)isrepresentedbyahexadecimalpairofnumbers(from00toff,e.g.,e7),andeachpairofbytesis
separatedfromthenextpairbyacolon.Anexampleis30c1:0ab6:0000:0000:0000:8a2e:0370:2f8e.For
awhile,theremaybealotofzerosinIPv6addresses,andtheycanbeskippedwiththeinsertionofa
doubleͲcolon,asinthisnotationofthepreviousaddress:30c1:0ab6::8a2e:0370:2f8e.
OneoftheprimaryimprovementsofIPv6overIPv4isitsallowanceoffarmoreIPaddresses.Thisisa
realissuegiventheexpectationthatsomanydevicesinthefuturewillrequireuniqueIPaddresses.
IPv6’s128Ͳbitrangeprovidesmorethan3.4x1038possibleaddresses,ormorethan5,000addressesper
squaremicrometeroftheEarth’ssurface–probablyenoughtolastforawhile.
Nevertheless,itisexpectedthatIPv4willremainthestandardformatoftheInternetforsometimeto
come,whileIPv6supportisgraduallydeployedworldwide.
ThereasonthatIPaddressesareimportanttothisdiscussionisbecausetheyessentiallyreplacethe
audiocrosspointsinatraditional,circuitͲswitchedenvironment.InanIPAudiosystem,alltrafficflows
alongasingle,serializedpath,andeachpacketofdatagetstoitsintendeddestinationviatheIPaddress
initsheader,ratherthanbyitsbeingsentalongadedicatedwirebyaswitcher.
2
IPv4hasbeeninusesince1981,establishedwiththepublicationbyDARPAoftheseminalRFC791document,
generallycitedastheoriginalspecificationfortheInternet.Althoughotherprotocolsprecededit,formostofus,
IPv4istheonlyversionofIPtheInternethaseverused.
3
Ifyou’rewonderingwhathappenedtoIPv5,itwasascribedtoaversionthatwasoriginallyintendedtobeused
forconnectionͲbased(ratherthanpacketͲbased)streamingmediaontheInternet,butworkwasabandonedonit
asstreamingmediabecamepossiblewiththedevelopmentofnewprotocolsoverIPv4.
UsingIPforBroadcastStudioAudio
ƒ‰‡͵
IPBeyondtheInternet
Asnotedearlier,IPisusedtodayonmanylocalareanetworksthatarenotconnectedtotheInternet.
ThisiswhytherearealargenumberofIPaddressesthatarereservedfornonͲInternetusesonprivate
networks. 4 AnumberofIPaddressrangesareinternationallyagreedtobereservedforthispurpose,the
largestcontiguousgroupofwhichspansfrom10.0.0.0to10.255.255.255.Thisgroupaloneprovides
some16millionpossibleaddressesthatarenotaccessiblefromtheInternet(routersareprogrammed
toignoretheaddressesonincomingInternettraffic),andareonlyavailablefromwithinalocalnetwork.
ThisalsoimpliesthataprivateIPaddresshasnoneedtobegloballyunique,andsothesesame
addressescanbeusedbyanyentityonitsinternalnetwork,therebyconservingthenumberofIP
addressesrequiredworldwide.
DevicesassignedsuchprivateaddressescanstillaccesstheInternetifnecessary,viaaproxyserveror
NetworkAddressTranslation(NAT)device.5
TheprivateaddressspaceisparticularlyusefulforstudioaudioapplicationsofIP,sincethedevicesso
interconnectedaretypicallynotintendedtobeaccessibledirectlyviathepublicInternet.
“IPbutnotInternet”isalsothecaseforanothermajoremergingtechnologycalledIPTV,whichusesIP
fordistributionoftelevisionprogramming,butoverdedicatednetworksoperatedbytelcos(providinga
multichannelservicecompetitivewithdigitalcableandsatelliteTV),nottheopenInternet. 6 StreamingChangesAll
Althoughoriginallydevelopedforstandarddatacommunication,subsequentenhancementstothe
Internetallowedittobeusedformediatransmission,aswell,whichiswellknownastheprocesscalled
streamingmedia.
ThisdevelopmentfundamentallyalteredtheusageoftheInternet,andhassubsequentlyhadsignificant
impactonallfacetsofthemediaindustry,astheystruggletocopewiththechangesitbrings,andto
takeadvantageofthenewopportunitiesitengenders.
BesidesspawningmanycurrentlyburgeoningonͲlinemediabusinesses,streamingtechnologyisalsothe
basisforIPstudioaudio.Thisallowstheaudiostudioenvironmenttoleverageseveralkeypropertiesof
anIPͲbasedenvironment,whichprovidesubstantialimprovementovermoretraditionalapproaches:
4
ThesenetworksuseaddressesintheprivateIPaddressspace,asspecifiedintheInternetEngineeringTask
Force’s(IETF)RFC1918,andadministeredbytheInternetAssignedNumbersAuthority(IANA).
5
NotethatinIPv6therewillbenoprivateaddressspaceorNAT,giventhefargreaternumberofgloballyuniqueIP
addressesitprovides.
6
Meanwhile,TVcontentsentviaIPthatdoestravelviatheopenInternet(“InternetTV”)isalsosoaringin
popularity,increasinglyusedfordistributionofbroadcastcontentaswellascontentcreatedbyconsumers(userͲ
generatedcontent,or“UGC”).
UsingIPforBroadcastStudioAudio
ƒ‰‡Ͷ
x
x
x
x
Scalability:PerhapsthemostfundamentalchangebetweenIPͲbasedaudiosystemsand
traditionalapproaches–analogordigital–istheabilityofIParchitecturestoadapttochange
andgrowth.Forexample,atraditionalaudioenvironmentmusthaveitsspatialorimaging
format(e.g.,mono,stereoorsurround)predetermined,alongwiththenumberofsimultaneous
audiochannelsitwillrequires(e.g.,one,twoormore).AnIPAudioenvironmenthasnosuch
requirement,andcaneasilyadapttoanyformat.Similarly,atraditional“crosspoint”audio
routingswitchermusthaveitsinputandoutput(I/O)configurationfixedinitshardwaredesign.
Inthisway,suchadevicereflectscircuitswitchingandparalleldesign,whereasIPAudiosystems
implementpacketswitchingandserialdesign.Thisallowsgreatflexibilityandresponsivenessin
accommodatingchangesinI/Oconfiguration.JustastelcoshavemovedawayfromthecircuitͲ
switchedpathsoftheirearlieryearsforsimilarreasons,studioaudiosystemscannowenjoythe
sameadvantagesofscalabilityandflexibilitytoimplementexpansioninanydimension.This
comesnotamomenttoosoon,giventhecompetitivepressurescomingtobearonbroadcasters
forincreasedcontentandlistenerchoice.
CostͲeffectiveness:Atalmostanyreasonablesize,anIPͲbasedaudiosystemwillcompare
favorablywiththecostofatraditionalsystem–bothintermsofhardware/materialspricingand
installationcost.Thereductioninwirealoneprovidessubstantialeconomy. 7 Maintenance
expensesaregenerallyalsolower.Thesecostdifferentialsincreasewiththesizeofthefacility,
whichiswhysomanylargerinstallationshavealreadymovedtoIPͲbasedsolutionsastheir
needshavecalledfornewtechnicalplants.
Convenience:Thesmallphysicalfootprint,lowoperatingcost,easeofreconfigurationor
upgrade,andfastinstallationofIPAudiosystemsmakethemextremelyconvenientfor
engineeringandoperationsalikeattheaudiostudiofacility.Frominitialdesignto
implementationtodailyoperation,IPͲbasedsystemsmakelifeeasier.
FutureͲproofing:Nothingstrikesfearintheheartoftheengineerormanagermorethan
makingapoormajorpurchasingdecision.MovingtoanIPͲbasedaudioarchitecturetakesalot
ofthepressureoff,sinceitofferssuchflexibilityandallowsbroadabilityforreconfiguration
downtheroad.Provisioningforunforeseenchangesismuchlessproblematicandcheaper.
NotethattheaboveadvantagesonlyfullyapplytosystemsthatutilizestandardIPintheirarchitecture.
Notallaudiosystemsthatusecomputernetworking(overEthernetand/oronRJ45connectors)for
interconnectionarenecessarilytrueIPͲbasedsystems.SomesimplyuseEthernetasaphysicallayerwith
aproprietarydataformataboveit, 8 whileothersmayusemoreIPͲlikeformatsbutwithnonͲstandard
7
RememberthatapacketͲswitchedsystemlikeIPdoesnotrequireindividualwiringpathstoeachinputand
outputofeverydevice.Forexample,anaudiomixingconsoleormultitrackrecordingdevicecanhaveallofits
inputsandoutputsinterfacedtotherestofthefacilityviaasinglecableinanIPAudioenvironment.
8
e.g.,Cobranet
UsingIPforBroadcastStudioAudio
ƒ‰‡ͷ
protocolvariations.SomeofthesenonͲstandardapproachesmayhaveofferedsomevalueinthepast
(suchasreducedoverheadandlatencyoverstandardIPnetworking),butgiventhecapacity,speedand
performanceofaproperlyconfigured,standardIPsystemtoday,thepenaltiespaidbyworkinginanonͲ
standardenvironmentgenerallyfaroutweighanyadvantagesthatsuchvariationsmightprovide,
particularlywhenconsideredoverthelongterm.
IPǦAnything
Intermsofcriticalmassbehindthistrend,studioaudioiscertainlynotaloneinitsmovementtowardIPͲ
basedprocesses,asalreadynoted.NumerousotherindustrieshavealreadyembracedatransitiontoIP
forsimilarreasonstothosecitedaboveforstudioaudio.
OnesuchdevelopmentthatiscloselyrelatedisVoiceͲoverͲIP(VoIP),whichisrapidlygaininggroundin
thetelephonyspaceasareplacementfortraditionalvoiceservice,inbothconsumerandenterprise
applications.AgaintheleveragingofIPasamechanismtousegeneralizedsystemsandtransportpaths
forvariousspecifictaskshasundeniableappeal,andthisargumentisalsofindingfavorinawiderange
ofotherindustries,fromhotelTVsystemstohealthcare.EmergingdigitalTVsystems(includingnew
mobilevariants)arealsofavoringanIPdistributionmodel.
IPisfastbecomingthelinguafrancaofdigitaltechnologyandcontent,allowinganythingexpressedin
itstermstobecarriedandprocessedthroughincreasinglyavailableandcostͲeffectiveinfrastructures.
JustasthePCbecamethegeneralpurposecomputingplatform(deliveringunprecedentedprocessing
power,speedandcostͲeffectiveness),IPhasbecomethegeneralpurposedatatransportformat.
Forengineers,familiaritywithdigitalnetworkingtechnologies,includingIP,hasbecomeanearͲ
requirementofthejobanyway(forimplementingtheonͲlineservicesofaradiostation),sowhynot
applythisknowledgetostudioaudio,too?
It’sbecomingclearthatIPistrulythewayofthedigitalmediaworld,particularlyforanyindustrythat
valuesconnectedness,agilityandcosteffectiveness.Intheradioenvironment,it’snotanoverstatement
tosaythatIPAudioisthefutureofstudioaudiosignalflow.Arguingotherwiseisdifficult:Thereisand
willcontinuetobesomuchdevelopmentwithintheIPenvironment,itonlymakessensetoharnessthe
powerofthateffort,whilealsolettingMoore’sLawhaveitsfulleffectonthehardwaresideforstudio
audioequipment,justastheseforces’effectsarebeingenjoyedbysomanyotherindustriestoday.
What’sthecatch?
Thisisnottosaythattherearen’tsomechallengestotheoptimaluseofIPforstudioaudiotransport.
PrimaryamongtheseisthelatencythattheencapsulationprocessofaudiodataintoIPpacketscan
cause,andtheirserialroutingthroughapacketͲswitchednetworkpronetodatacollisions.As
mentionedearlier,variousmethodshavebeenputforthbydeveloperstoamelioratethis,butproper
UsingIPforBroadcastStudioAudio
ƒ‰‡͸
configurationofavailabledevicesusedontoday’shighͲspeedEthernetnetworksisusuallyadequateto
resolveanysuchdifficultiesinIPAudiosystems.
SuchconfigurationofstandardIPequipment(e.g.,Ethernetroutersandswitches,buffersizesand
networkspeeds)canbesettooptimallyservethespecificneedsofastudioaudiosystem,ratherthan
generalizedInternetdatatraffic.Forthisreason–aswellasforobvioussecuritypurposes–itis
importanttouseaseparate,dedicatednetwork(eitherphysicalorvirtual)forallstudioaudioIP
applications.Thisnetworkcancarryallaudiocontent,controlsignalsandmetadatarelatedto
production,butshouldbeisolatedfromthegeneraldatanetworkofthefacility.Inaddition,there
generallyshouldnotbeadirectconnectionofthestudioaudiosystemtothepublicInternet.When
InternetconnectionsarerequiredforaccesstooffͲsiteaudiosourcesordestinations,theyshouldbe
routedthroughaproxyserverorotherisolatingpath.SomevendorswillalsosetIPpacketprioritization
atahigherlevelforaudiocontentpacketsthanforgeneralnetworkdata.ThishelpsIPAudio
performanceevenonnetworksthatarenotdedicatedtoIPAudiousageonly.
Anotherissueisasimpleoneofconnectorstandards.SinceIPAudiogenerallytravelsonCAT5orbetter 9 Ethernetcables,theRJ45connectorisusedforallterminations.ButsomeIPAudiosystem
implementersalsouseRJ45foranalogorAES3digitalaudioI/Oandpatching.Whilethiscanminimize
thenumberofdifferentconnectortypesusedinafacility,andreducethephysicalspacerequiredfor
connectorpanels,thereisnostandardfortheconfigurationofanRJ45connectorforthispurpose.So
individualIPAudioimplementershavedesignedtheirownunilateralformats,againpossiblylimiting
broadcasterstotheuseofonlycertainmanufacturers’productsinanIPAudiofacility,orrequiringthe
useofadapters.
Ofcourse,theneedtoretaincompatibilitywithanalogandAES3digitalaudiowilllikelyremainforsome
timetocomeatanyIPͲbasedaudiofacility.Attheveryleast,livemicrophonesignalswillneedtobe
convertedfromtheirnativeanalogaudio(orinsomecases,perhapsAES3)format,andinsomecases
analogordigitalaudiofromotherdevicesorremotesourceswillalsohavetobeaccommodated.How
thisconversionprocessisaccomplishedisakeyfactorinthedesignofanIPAudiosystem.
Forthetimebeingatleast,theaboveoptimizationprocessesarguefortheselectionofasinglevendor
forthesupplyofIPAudioequipmenttoagivenbroadcastfacility,oratleasttheverificationthat
compatibilityamongdifferentvendors’IPAudioequipmentisassured.Workingwithasinglesupplier
alsoensuresthatupdatesandupgradeswillbedeliveredinatimelyfashion,andevenspecialfixesfora
particularproblemencounteredatagivenfacilitycanbequicklyprovided.
9
CAT5eorCAT6
UsingIPforBroadcastStudioAudio
ƒ‰‡͹
Implementationandintegration
ThisbringsustoactualIPAudiosystemconsiderations.Giventheadvantagesofscaleprovidedbythese
systems,itmakessensetomaketheIPAudiodomainaslargeaspossiblewithinagivenfacility.That
impliesthataudiosignalsinotherformsshouldbeconvertedtoIPpacketsassoonaspossible.
Thebestplacetodothisinmoststudioconfigurationsisatthecentralpatchbayand/orthestudio
mixingconsole(s).Microphoneoutputsandsignalsfromother“legacy”audiosourcescanbe
immediatelyconvertedtodigitalaudioform(iftheyaren’talready)andpacketizedasIP.OnceintheIP
domain,thesesignalscanbeaddressedandroutedtoanyotherlocationonthenetwork.Thiscan
includedestinationswithintheconfinesofafacilityviaLAN,oranywhereintheworldviaWAN.
Anotheradvantageofthisapproachisthatamixingconsolecanactasarouter.Inotherwords,because
anyinputontheconsolecanhaveauniqueIPaddress,itcanbeconnectedtoanyIPAudiosourceon
thenetwork.(Evenmoreamazingtoveteranaudioengineersisthatthiscanbeaccomplishedeven
thoughtheentireconsoleisconnectedtothenetworkviaasinglecable.)Acentralswitchingcontrol
unit(typicallyaPC)canassigntheseI/Oconnections,orthemixingconsoleitselfcanhaveacontrol
interfaceforthispurpose.Inaddition,standalonehardwareswitchcontrollerscanbedistributedaround
thefacility,essentiallyduplicatingtheappearanceandfunctionoftraditionalrouterͲcontrolpanels.Inall
cases,however,allthatisbeingdonetoachievetheroutingistheadditionofappropriateIPaddresses
totheheadersofIPAudiopacketsonthenetwork. 10
Ofcourse,themixingconsolecanalsobeequippedwithtraditionalanalog(mic/line)orAES3inputson
someinputsaswell,toaccommodatelocalaudiosourcedevices.Thesesourcesareinturnconvertedto
IPbytheconsole,andviatheirroutingtotheconsolebusordirectoutputs,thesesignalsmayinturnbe
madeavailableasIPsourcestotherestofthenetwork–againviathesinglecableconnectingthe
consoletothenetwork.(SeeFigure1.)
ConsideralsohowPCͲbasedaudioplayout/automationsystemscanbeinterfacedtosuchasystem.
RatherthantheiraudiooutputsbeingdirectedthroughPCsoundcardstotraditionalaudioinputs,the
automationsystemcanbefittedwithanIPdriverthatprovidesasoftwareinterfacebetweenthePC
audioandtheIPnetworkdirectlyintheIPAudiodomain.Thisnotonlymaintainshighaudioquality,but
cutscostsintheautomationsystemsinceno(oratleastfewer)soundcardsarerequired.TheIP
interfacecanalsocarrycontroldataandPADaswell,eliminatingtheneedforseparatedatalinks
betweendevices.
10
Ideally,theIPfeedsto/fromanymixingconsoleinanIPAudiosystemareusedonlyforthoseitemsthatneed
accesstotheconsole’saudiomanipulationfeatures.SimpleinputͲtoͲoutputconnectionscanbehandledbythe
coreIPAudioarchitecturewithouttakingupconsoleresources(orevenusingupacrosspoint,intraditional
switchingterms).TheconsolecanbeconsideredasanIPapplianceor“audioengine,”whichcanhostanysortof
audiolevelͲadjustment,mixing,processingorcoding/transcodingthatthefacilityrequires,applyingallsuch
processesefficientlyandwithintheIPdomain.
UsingIPforBroadcastStudioAudio
ƒ‰‡ͺ
Moreover,asingleIPdriverinterfacebetweenanautomationsystemandanIProutingarchitecturecan
Moreover,asingleIPdriverinterfacebetweenanautomationsystemandanIProutingarchitecturecan
carrymanyindependentaudiochannels(perhapsupto24),whereasatraditionalswitchingsystem
carrymanyindependentaudiochannels(perhapsupto24),whereasatraditionalswitchingsystem
wouldrequireacrosspoint(pluswiring)foreachsoundcardinputandoutput.Thecombinedhardware
wouldrequireacrosspoint(pluswiring)foreachsoundcardinputandoutput.Thecombinedhardware
savings(soundcards+crosspoints+wire+installation)inalargefacilitycouldbesubstantial.
savings(soundcards+crosspoints+wire+installation)inalargefacilitycouldbesubstantial.
AnyIPAudiosystemtodaywillalsoincludeoneormorestandardEthernetswitches,whichareusedto
AnyIPAudiosystemtodaywillalsoincludeoneormorestandardEthernetswitches,whichareusedto
interconnecttheEthernetconnectionsfromeachfacilityordevicethatprovidesaudioI/OviaIP.These
interconnecttheEthernetconnectionsfromeachfacilityordevicethatprovidesaudioI/OviaIP.These
switchesarestandardtelecomdevices,whichreplacethemorecommonEthernethubsorroutersused
switchesarestandardtelecomdevices,whichreplacethemorecommonEthernethubsorroutersused
forsimilarRJ45terminationsintypicalhomeorsmallofficesituations.SwitchesarepreferredinIP
forsimilarRJ45terminationsintypicalhomeorsmallofficesituations.SwitchesarepreferredinIP
Audioapplicationsbecausetheyhavemoreintelligencethanhubs,whichallowsthemtoinspectdata
Audioapplicationsbecausetheyhavemoreintelligencethanhubs,whichallowsthemtoinspectdata
packetstodeterminetheirsourceanddestination,andforwardthemappropriately.Throughthis
packetstodeterminetheirsourceanddestination,andforwardthemappropriately.Throughthis
intelligentcontrol,eachmessageisonlysenttotheintendeddevice,therebyconservingnetwork
intelligentcontrol,eachmessageisonlysenttotheintendeddevice,therebyconservingnetwork
bandwidthandprovidingbetterperformance(includingreducedlatency).
bandwidthandprovidingbetterperformance(includingreducedlatency).
Local
Local
Audio
Audio
Sources
Sources
Conversion
ConversionIPͲbasedMixing
toIP
toIP
Console
IPͲbasedMixing
Console
(Mic/line
(Mic/line
Analogor
Analogor
AES3)
AES3)
EthernetSwitch(Edge)
EthernetSwitch(Edge)
Ethernet
Ethernet
LAN LAN
Ethernet
Ethernet
Switch
Switch
(Core)
(Core)
To/fromIPͲSTLs&
To/fromIPͲSTLs&
OtherSites
OtherSites
WAN WAN
LANorWAN
LANorWAN
Softwareinterface
Softwareinterface
(audio+control)
Ethernet
Ethernet
LAN
LAN
To/fromOther
To/fromOther
Studiosinthe
Studiosinthe
Facility
Facility
LAN
To/from
Internet
To/from
Internet
RadioServers
RadioServers
LAN
(audio+control)
IPAudio
IPAudio
Converter
Converter
PCͲbasedAudio
PCͲbasedAudio
Storage/automation
Storage/automation
System
System
(w/IPDriverSoftware)
(w/IPDriverSoftware)
IncomingRemoteAudio+
IncomingRemoteAudio+
ControlSignals
ControlSignals
STUDIO
STUDIO
TOC
TOC
ProgramOutputs
ProgramOutputs
toAudio
toAudio
Processors,
Processors,
ConventionalSTLs,
ConventionalSTLs,
Monitoring,etc.
Monitoring,etc.
(AES3orAnalog)
(AES3orAnalog)
Figure1:ConceptualblockdiagramofatypicalIPAudioͲbasedbroadcaststudiofacility,showingonestudioand
Figure1:ConceptualblockdiagramofatypicalIPAudioͲbasedbroadcaststudiofacility,showingonestudioand
TechnicalOperationsCenter(TOC).
TechnicalOperationsCenter(TOC).
Ethernetswitchescomeinunmanagedormanagedforms,thelatterallowinguserconfigurationof
Ethernetswitchescomeinunmanagedormanagedforms,thelatterallowinguserconfigurationof
variousparametersoftheswitch’soperation.InsmallerIPAudiofacilities,unmanagedswitchescan
variousparametersoftheswitch’soperation.InsmallerIPAudiofacilities,unmanagedswitchescan
performadequately,whilelargerfacilitiesmaybenefitfrommanagedswitches.Someswitchesalso
performadequately,whilelargerfacilitiesmaybenefitfrommanagedswitches.Someswitchesalso
UsingIPforBroadcastStudioAudio
UsingIPforBroadcastStudioAudio
ƒ‰‡ͻ
ƒ‰‡ͻ
includeremoteadministrationcapability.Today’sfastestswitchesoperateatGigabitspeeds,usingCAT6
cable,andthesearethemostappropriateforlowͲlatencyIPAudioapplications.
AsFigure1indicates,atypicalIPAudiofacilityincludesmultipleswitches,usuallyarrangedwithone
large(“core”)switchinacentralroom,andsmaller(“edge”)switchesplacedasneededinotherrooms
aroundthefacility.Suchdistributedroutingintelligenceimprovesperformance,andalsoprovides
redundancyincaseofswitchfailure.
NotealsothattheproliferationofVoIPandotherrealtimeapplicationsviaIPhavespawnedbroad
implementationofnonͲblockingarchitectureinrecentEthernetswitches.Thisapproachvirtually
eliminatesdatacollisionswithinaswitch,whilemaintainingcostͲeffectiveness,byensuringjustͲ
adequatecapacityfornxnconnectivity 11 throughtheswitchingfabric.MissionͲcriticalperformanceis
therebymaintainedbyusingEthernetswitchesthatimplementnonͲblockingdesign,andwhenproperly
implementedwithinanIPAudiosystem,switchcapacityshouldneverbeexceeded.MostIPAudio
vendorsrecommendonlynonͲblockingEthernetswitches,andthisisonereasonwhyusersshouldheed
vendors’recommendationsforallswitchesusedintheirfacilities.(Again,theeconomyofscaledriven
bybroaduptakeoftheseswitchestodayprovidessuchadvantagestoIPAudioimplementersatvery
attractiveprices.)
TheuseofEthernetswitchesbymissionͲcriticalandotherhighͲreliabilitytelecomoperationshasdriven
majormanufacturerstoprovideexcellent24x7andovernightͲreplacementsupport.Notealsothatasa
facilitygrows,itmayneedtoreplaceolderswitcheswithnewermodels;thefactthatEthernetisa
ubiquitousstandardmeansthatallupgradeswillremainbackwardcompatible.Meanwhile,Moore’s
Lawensuresthatassuchnewhardwarebecomesavailable,price/performanceratioswillcontinually
improve.
TheIPAudiodomainisalsoextendingbeyondthestudio.Figure1showshowIPAudioisconvertedback
toAES3(orevenanalog)forprogramoutputs’connectiontoconventionalStudioͲtoͲTransmitterLinks
(STLs),butthediagramalsoindicatesthatanSTLcouldcarryIPAudiotothetransmittersite(viaWANor
otherdedicatedlink).WhetherleasedfromtelcoorusingastationͲoperatedRFpath,ifadequate
bandwidthisavailable,multipleaudiochannels,controlandmetadatacanallbecarriedviaIPonthe
link–bidirectionally,ifdesired–withminimallatency. 12
IPAudioinUseToday
TheadvantagesofIPAudiohavebeennoticedbybroadcastersandstudioownersaroundtheworld.Itis
fairtosaythattheengineersdesigningeverynewbroadcaststudiofacilitybuilttoday(andfromthis
pointforward)areatleastconsideringtheuseofanIPAudioarchitecture–andmanyofthemare
decidingtotaketheplunge.Speakingwiththemafterwardswillfindalmostunanimousagreementthat
11
12
Inotherwords,anyinputontheswitchcanalwaysbeconnectedtoanyoutputontheswitch,underanyusage.
BidirectionallinkscansubstantiallydecreasejitterandlatencycomparedwithunidirectionalIPpaths.
UsingIPforBroadcastStudioAudio
ƒ‰‡ͳͲ
itwastheproperchoice,andthere’snolookingback.Inmanycasesyouwillhearthatthetransition
processwasfareasierthantheyexpected.
TheinstallationofanIPAudiosystemmakesmanypeopleattheoperationhappy,fromtheCEtothe
CFO.ThetotalcostofbuildingandoperatinganIPAudiofacilityissignificantlyreduced,andyetthiscan
beaccomplishedwithoutgivingupflexibility–infactit,too,isgreatlyincreased.Operationsareoften
minimallyinterrupted,aswell,duetothesmallfootprintandquickinstallationofIPAudiosystems.
Thisiswhybroadcastersofallstripes,andwithbudgetslargeandsmall,havemovedtoIPAudio
systems.OnthecommercialsideintheU.S.,broadcastersfromClearChanneltoGreaterMediahave
recentlyinstalledIPAudiosystems,whilenonͲcommercialoperatorsfromMinnesotaPublicRadioto
WYMS,Milwaukeehavedonethesame.
Infact,theclienteleforthisemergingtechnologyalmostdefiescharacterization.Itincludessmall
independentstations,collegeradio(includingnumerousruralandcommunitycolleges),ethnicand
religiousbroadcasters,satelliteradioservices,radioandtelecomnetworkoperators,contentproduction
andbroadcastoriginationsites,corporatefacilitiesandgovernmentagencies–alongwithsomeofthe
largestandmostrespectedstationsinthecountry.
NeitherisadoptionisbyanymeanslimitedtotheU.S.IPAudioisalreadywellensconcedaroundthe
world,fromSpaintoSouthAfrica,fromItalytoIsrael,fromChinatotheCzechRepublic,andmanyother
placesinbetween.
Clearlythetechnologyhasalotofuniqueadvantagestooffer,andthesehavebeennoticedbymanyof
theleadingpurveyorsofaudiocontentanddeliverythroughouttheplanet.
Conclusions
It’snotoftenthatanewtechnologyoffersconsiderabletechnicalimprovement,easierinstallationand
maintenance,greatlyenhancedflexibilityandscalability,andreducedcostwhencomparedwithits
predecessors.YetthesearetheattributesofaproperlyimplementedIPAudiosystem.
BroadcastershavealwaysbeenacostͲconsciouslot,andrightlyso,butgiventoday’sincreasingly
competitivelandscape,efficienciesincapitalexpendituresandoperatingcostshavebecomeevenmore
criticalanddesirable.
Meanwhile,it’sbecomequiteclearthattheradioindustrywillfacesubstantialchangeinthenear
future,andmuchofitwilllikelyinvolvequantitativegrowthinservices.Morestreams,moreaudio
channels,moredata,moreresponsivenesstoaudiencedemands,andprobablymorestill,areallonthe
paththatliesaheadforbroadcasters.AnIPAudioplatformprovidesalegitimateplatformtomost
realisticallyaccommodatethesemanychallenges.
UsingIPforBroadcastStudioAudio
ƒ‰‡ͳͳ
Itbehoovesanybroadcasterfacedwiththeopportunitytoconfronttheseuncertaintiestoseekthe
counselofexpertsinthefieldofIPAudio,andtobenefitfromtheexperienceofthosewhohave
recentlyundertakensimilarprojects.YouwilllikelyhearstrongencouragementtomakethemovetoIP,
justasmuchoftherestoftheworldisdoing,withgoodreason.
Fairfax,VA
February2008
UsingIPforBroadcastStudioAudio
ƒ‰‡ͳʹ
Axia Audio, a Telos Company • 2101 Superior Ave. • Cleveland, Ohio, 44114, USA • +1.216.241.7225 • www.AxiaAudio.com