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Using IP for Broadcast Studio Audio


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SkipPizzi

ExecutiveSummaryArevolutioniscurrentlytakingplaceinthefieldofaudiostudiodesign.Itinvolvesafundamental

rethinkingofthewaysignalsaredistributedandmanagedthroughoutthebroadcastfacility.

AnewapproachtothisprocessutilizesadigitaltransmissionformatsimilartothatusedontheInternet

forpurposesoftransportanddistributionofcontentaroundanaudioproductionenvironment.

ThisformatisknownastheInternetProtocol,generallyreferredtoasIP,anditistheverycoreoftheInternet.IPisthecommonformatusedforanykindofdatathatflowsontheInternet(including

streaming

media),

and

on

private

extensions

of

the

Internet,

such

as

the

LANs

employed

in

enterprise

networksandsmalloffice/homeoffice(SOHO)networks,bothwiredandwireless.Itsetstherulesfor

thisentiredatanetworkinginfrastructure,bothhardwareandsoftware,whichhasemergedandbeen

sobroadlyembracedoverthelastquartercenturyormore.Sincemostaudiofacilitieshavealready

convertedtodigitalaudio,itthereforemakessensetonowexaminetheuseofIPthere,aswell.

GiventhatIPisthelinguafrancaofcontemporarydatanetworking,itcanprovidesignificanteconomiesofscaleforspecializedapplicationssuchasprofessionaldigitalaudiodistribution.Thisexploitsthesame

processthathasmadethegeneralpurposedesktopcomputeranefficientandcosteffectiveplatform

forthecreationandstorageofprofessionalaudiocontent.IPAudiodistributionissimplyanextension

ofthatthinkingandtechnology,replacingthepurposebuilt(andrelativelyexpensive)mixers,routers

andswitchersthathavetraditionallybeenusedbyaudiostudiosformanagingmultipleaudiosignalsas

theypassthroughaproductionorbroadcastfacility.IPalsoallowsthefullandcontinuingforceof

MooresLawtobeappliedtoaudiodistribution,justasthePChasdoneforotheraudioprocesses.

Beyondsimplecosteffectiveness,however,IPAudiooffersotherimportantbenefits.Theseincludehigh

scalability(i.e.,theabilitytoeasilyaccommodategrowthandotherconfigurationchanges),convenience

(i.e.,easyandfastinstallation)andfutureproofing(i.e.,highlikelihoodoffittingwellintoanyscenario

forfuturefacilityrequirements).Puttingalltheseelementstogethercreatesavaluepropositionthatis

hardtoignorewhenconsideringoptionsfornewfacilitydesignsorexistingstudioupgrades.

ManyotherindustrieshavealreadyconvertedtheirlegacycommunicationsprocessestoIPbased

replacementsystems.StudioaudiosystemsusingIPbasedtechnologyarenowsufficientlymatureto

allowaudioproducersandbroadcasterstodothesame,providingthemwithsubstantialsavingswhile

simultaneouslypositioningthemwelltoaccommodateindeterminatefutureneeds.

UsingIPforBroadcastStudioAudio


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IntroductionThispaperconsidersthereplacementoftraditionalformsofaudiosignaltransportinthebroadcast

studiowithnetworkedaudiocarriedviaInternetProtocol(IP).Itexaminesthevalueandprocessofsuch

conversion,thechallengestodoingso,andthelikelyfutureofthisenvironment.

ThisstudywascommissionedbyAxiaAudioinearly2008.

ABriefHistoryThebroadcastaudiostudiohasalonglegacyrelationshipwiththetelecommunicationsworld.The

earliestaudiofacilitiesandstandardpracticesweredevelopedbyBellSystemandWesternElectric

engineersintheearly20th

century,andthetwoworldshaveneverstrayedfarfromeachothersince.

Inparticular,broadcastaudiohasretainedacloseconnectiontothetelecomenvironment,sinceso

muchofbroadcastingscontentcomesand/orgoesfromthestudioviatelcoprovidedpaths.

Thusit

is

not

surprising

that

the

next

generation

of

studio

audio

technology

should

once

again

follow

a

pathblazedbytelecommunicationstechnologies.

Inthiscase,thetechnologyinvolvesdigitalnetworkingspecificallyusingthepopularandnownearly

ubiquitousInternetProtocol(IP).Thisprotocol,coupledwitheithertheTransmissionControlProtocol(TCP)orUniversalDatagramProtocol(UDP)datatransportformat,providesthebulkofdatacommunicationcarriedontheInternet.Itspopularityforthatpurposehasalsomadeitusefulforother

localized,nonInternetdatanetworkingpurposes.Thisisprimarilyduetothevolumeofdevelopment

andresultinghardwareandsoftwarethatsupportsTCP/IPorUDP/IP,andthegreateconomyofscale

thatresults.

Foralittlebackground,notethataprotocolinthedatanetworkingcontextissimplyanagreementon

theformatofdatathatwillbepassedbetweendevices.Thereforeitspecifiesasetofrulesforvarious

parametersofthatdata,suchasthedataratesallowed,theerrorcheckingalgorithmsemployed,any

datacompressionformatsthatmightbeused,howthestartandendofindividualmessageswillbe

determined,howconfirmationthatamessagehasbeensuccessfullydeliveredwillbecommunicated,

andsoon.

ItsalsohelpfultoreviewsomeoftheearlydevelopmentthatledtoIPsparticularpopularity.Ina

nutshell,theIPapproachisasimplificationofthecanonicalsevenlayernetworkingarchitecture1down

toastackconsistingofonlyfourlayers,asshowninTable1.

1TheOpenSystemsInterconnection(OSI)referencemodel,establishedinthelate1970s,includedApplication,

Presentation,Session,Transport,Network,DataLink,andPhysicallayers.



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APPLICATION HTTP,RTP,FTP,SMTP,TELNETTRANSPORT TCP,UDPNETWORK IP

LINK Ethernet,WiFiTable1:ThefourlayersofInternetdatatransmission,withsomeexamplesofeachlayersprotocols.

TheInternetprocessalsoincludesanaddressingprotocolforeachofitsdatapackets,theIPaddress.AnydeviceattachedtoanIPnetworkisassignedanIPaddress.Untilrecentlyi.e.,usingIPv4anIP

addresswasspecifiedasanumericstringoffouronebytenumbers(oroctets,sinceonebyteiseight

bits),eachexpressedindecimalform(from0to255)andseparatedbyperiods(e.g.,169.10.206.2).2

ThisimpliesthatthenumberofpossibleaddressesinIPv4isthatexpressedbya32bitnumber(4x8

bits),meaningthat232,orapproximately4.3billion(4.3x10

9),uniqueIPaddressesareavailable.This

maysoundlikealot,butmanyofthesearereservedforspecificuses(moreonthisbelow).

Today,the

IP

world

is

converting

to

IPv6,

which

specifies

its

IP

addresses

using

128

bit

rather

than

32

bit

numbers.3

ThenumericalexpressionofIPv6addressesalsodiffersfromIPv4s,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

doublecolon,asinthisnotationofthepreviousaddress:30c1:0ab6::8a2e:0370:2f8e.

OneoftheprimaryimprovementsofIPv6overIPv4isitsallowanceoffarmoreIPaddresses.Thisisa

realissue

given

the

expectation

that

so

many

devices

in

the

future

will

require

unique

IP

addresses.

IPv6s128bitrangeprovidesmorethan3.4x1038

possibleaddresses,ormorethan5,000addressesper

squaremicrometeroftheEarthssurfaceprobablyenoughtolastforawhile.

Nevertheless,itisexpectedthatIPv4willremainthestandardformatoftheInternetforsometimeto

come,whileIPv6supportisgraduallydeployedworldwide.

ThereasonthatIPaddressesareimportanttothisdiscussionisbecausetheyessentiallyreplacethe

audiocrosspointsinatraditional,circuitswitchedenvironment.InanIPAudiosystem,alltrafficflows

along

a

single,

serialized

path,

and

each

packet

of

data

gets

to

its

intended

destination

via

the

IP

address

initsheader,ratherthanbyitsbeingsentalongadedicatedwirebyaswitcher.

2IPv4hasbeeninusesince1981,establishedwiththepublicationbyDARPAoftheseminalRFC791document,

generallycitedastheoriginalspecificationfortheInternet.Althoughotherprotocolsprecededit,formostofus,

IPv4istheonlyversionofIPtheInternethaseverused.3IfyourewonderingwhathappenedtoIPv5,itwasascribedtoaversionthatwasoriginallyintendedtobeused

forconnectionbased(ratherthanpacketbased)streamingmediaontheInternet,butworkwasabandonedonit

asstreamingmediabecamepossiblewiththedevelopmentofnewprotocolsoverIPv4.



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IPBeyondtheInternetAsnotedearlier,IPisusedtodayonmanylocalareanetworksthatarenotconnectedtotheInternet.

ThisiswhytherearealargenumberofIPaddressesthatarereservedfornonInternetusesonprivate

networks.4AnumberofIPaddressrangesareinternationallyagreedtobereservedforthispurpose,the

largestcontiguousgroupofwhichspansfrom10.0.0.0to10.255.255.255.Thisgroupaloneprovides

some16millionpossibleaddressesthatarenotaccessiblefromtheInternet(routersareprogrammed

toignore

the

addresses

on

incoming

Internet

traffic),

and

are

only

available

from

within

alocal

network.

ThisalsoimpliesthataprivateIPaddresshasnoneedtobegloballyunique,andsothesesame

addressescanbeusedbyanyentityonitsinternalnetwork,therebyconservingthenumberofIP

addressesrequiredworldwide.

DevicesassignedsuchprivateaddressescanstillaccesstheInternetifnecessary,viaaproxyserveror

NetworkAddressTranslation(NAT)device.5

TheprivateaddressspaceisparticularlyusefulforstudioaudioapplicationsofIP,sincethedevicesso

interconnectedaretypicallynotintendedtobeaccessibledirectlyviathepublicInternet.

IPbutnotInternetisalsothecaseforanothermajoremergingtechnologycalledIPTV,whichusesIP

fordistributionoftelevisionprogramming,butoverdedicatednetworksoperatedbytelcos(providinga

multichannelservicecompetitivewithdigitalcableandsatelliteTV),nottheopenInternet.6

StreamingChangesAllAlthoughoriginallydevelopedforstandarddatacommunication,subsequentenhancementstothe

Internetallowedittobeusedformediatransmission,aswell,whichiswellknownastheprocesscalled

streamingmedia.

ThisdevelopmentfundamentallyalteredtheusageoftheInternet,andhassubsequentlyhadsignificant

impactonallfacetsofthemediaindustry,astheystruggletocopewiththechangesitbrings,andto

takeadvantageofthenewopportunitiesitengenders.

Besidesspawningmanycurrentlyburgeoningonlinemediabusinesses,streamingtechnologyisalsothe

basisforIPstudioaudio.Thisallowstheaudiostudioenvironmenttoleverageseveralkeypropertiesof

anIPbasedenvironment,whichprovidesubstantialimprovementovermoretraditionalapproaches:

4ThesenetworksuseaddressesintheprivateIPaddressspace,asspecifiedintheInternetEngineeringTask

Forces(IETF)RFC1918,andadministeredbytheInternetAssignedNumbersAuthority(IANA).5NotethatinIPv6therewillbenoprivateaddressspaceorNAT,giventhefargreaternumberofgloballyuniqueIP

addressesitprovides.6Meanwhile,TVcontentsentviaIPthatdoestravelviatheopenInternet(InternetTV)isalsosoaringin

popularity,increasinglyusedfordistributionofbroadcastcontentaswellascontentcreatedbyconsumers(user

generatedcontent,orUGC).



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x Scalability:PerhapsthemostfundamentalchangebetweenIPbasedaudiosystemsand

traditionalapproachesanalogordigitalistheabilityofIParchitecturestoadapttochange

andgrowth.Forexample,atraditionalaudioenvironmentmusthaveitsspatialorimaging

format(e.g.,mono,stereoorsurround)predetermined,alongwiththenumberofsimultaneous

audiochannelsitwillrequires(e.g.,one,twoormore).AnIPAudioenvironmenthasnosuch

requirement,andcaneasilyadapttoanyformat.Similarly,atraditionalcrosspointaudio

routingswitcher

must

have

its

input

and

output

(I/O)

configuration

fixed

in

its

hardware

design.

Inthisway,suchadevicereflectscircuitswitchingandparalleldesign,whereasIPAudiosystemsimplementpacketswitchingandserialdesign.ThisallowsgreatflexibilityandresponsivenessinaccommodatingchangesinI/Oconfiguration.Justastelcoshavemovedawayfromthecircuit

switchedpathsoftheirearlieryearsforsimilarreasons,studioaudiosystemscannowenjoythe

sameadvantagesofscalabilityandflexibilitytoimplementexpansioninanydimension.This

comesnotamomenttoosoon,giventhecompetitivepressurescomingtobearonbroadcasters

forincreasedcontentandlistenerchoice.

x Costeffectiveness:

At

almost

any

reasonable

size,

an

IP

based

audio

system

will

compare

favorablywiththecostofatraditionalsystembothintermsofhardware/materialspricingand

installationcost.Thereductioninwirealoneprovidessubstantialeconomy.7Maintenance

expensesaregenerallyalsolower.Thesecostdifferentialsincreasewiththesizeofthefacility,

whichiswhysomanylargerinstallationshavealreadymovedtoIPbasedsolutionsastheir

needshavecalledfornewtechnicalplants.

x Convenience:Thesmallphysicalfootprint,lowoperatingcost,easeofreconfigurationor

upgrade,andfastinstallationofIPAudiosystemsmakethemextremelyconvenientfor

engineeringandoperationsalikeattheaudiostudiofacility.Frominitialdesignto

implementationtodailyoperation,IPbasedsystemsmakelifeeasier.

x Futureproofing:Nothingstrikesfearintheheartoftheengineerormanagermorethan

makingapoormajorpurchasingdecision.MovingtoanIPbasedaudioarchitecturetakesalot

ofthepressureoff,sinceitofferssuchflexibilityandallowsbroadabilityforreconfiguration

downtheroad.Provisioningforunforeseenchangesismuchlessproblematicandcheaper.

NotethattheaboveadvantagesonlyfullyapplytosystemsthatutilizestandardIPintheirarchitecture.

Notallaudiosystemsthatusecomputernetworking(overEthernetand/oronRJ45connectors)for

interconnectionarenecessarilytrueIPbasedsystems.SomesimplyuseEthernetasaphysicallayerwith

aproprietarydataformataboveit,8whileothersmayusemoreIPlikeformatsbutwithnonstandard

7RememberthatapacketswitchedsystemlikeIPdoesnotrequireindividualwiringpathstoeachinputand

outputofeverydevice.Forexample,anaudiomixingconsoleormultitrackrecordingdevicecanhaveallofits

inputsandoutputsinterfacedtotherestofthefacilityviaasinglecableinanIPAudioenvironment.8e.g.,Cobranet



7/14

protocolvariations.Someofthesenonstandardapproachesmayhaveofferedsomevalueinthepast

(suchasreducedoverheadandlatencyoverstandardIPnetworking),butgiventhecapacity,speedand

performanceofaproperlyconfigured,standardIPsystemtoday,thepenaltiespaidbyworkinginanon

standardenvironmentgenerallyfaroutweighanyadvantagesthatsuchvariationsmightprovide,

particularlywhenconsideredoverthelongterm.

IPAnything

Intermsofcriticalmassbehindthistrend,studioaudioiscertainlynotaloneinitsmovementtowardIP

basedprocesses,asalreadynoted.NumerousotherindustrieshavealreadyembracedatransitiontoIP

forsimilarreasonstothosecitedaboveforstudioaudio.

OnesuchdevelopmentthatiscloselyrelatedisVoiceoverIP(VoIP),whichisrapidlygaininggroundin

thetelephonyspaceasareplacementfortraditionalvoiceservice,inbothconsumerandenterprise

applications.AgaintheleveragingofIPasamechanismtousegeneralizedsystemsandtransportpaths

forvariousspecifictaskshasundeniableappeal,andthisargumentisalsofindingfavorinawiderange

ofotherindustries,fromhotelTVsystemstohealthcare.EmergingdigitalTVsystems(includingnew

mobilevariants)arealsofavoringanIPdistributionmodel.

IPisfastbecomingthelinguafrancaofdigitaltechnologyandcontent,allowinganythingexpressedin

itstermstobecarriedandprocessedthroughincreasinglyavailableandcosteffectiveinfrastructures.

JustasthePCbecamethegeneralpurposecomputingplatform(deliveringunprecedentedprocessing

power,speedandcosteffectiveness),IPhasbecomethegeneralpurposedatatransportformat.

Forengineers,familiaritywithdigitalnetworkingtechnologies,includingIP,hasbecomeanear

requirementof

the

job

anyway

(for

implementing

the

on

line

services

of

aradio

station),

so

why

not

applythisknowledgetostudioaudio,too?

ItsbecomingclearthatIPistrulythewayofthedigitalmediaworld,particularlyforanyindustrythat

valuesconnectedness,agilityandcosteffectiveness.Intheradioenvironment,itsnotanoverstatement

tosaythatIPAudioisthefutureofstudioaudiosignalflow.Arguingotherwiseisdifficult:Thereisand

willcontinuetobesomuchdevelopmentwithintheIPenvironment,itonlymakessensetoharnessthe

powerofthateffort,whilealsolettingMooresLawhaveitsfulleffectonthehardwaresideforstudio

audioequipment,justastheseforceseffectsarebeingenjoyedbysomanyotherindustriestoday.

Whatsthecatch?ThisisnottosaythattherearentsomechallengestotheoptimaluseofIPforstudioaudiotransport.

PrimaryamongtheseisthelatencythattheencapsulationprocessofaudiodataintoIPpacketscan

cause,andtheirserialroutingthroughapacketswitchednetworkpronetodatacollisions.As

mentionedearlier,variousmethodshavebeenputforthbydeveloperstoamelioratethis,butproper



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configurationofavailabledevicesusedontodayshighspeedEthernetnetworksisusuallyadequateto

resolveanysuchdifficultiesinIPAudiosystems.

SuchconfigurationofstandardIPequipment(e.g.,Ethernetroutersandswitches,buffersizesand

networkspeeds)canbesettooptimallyservethespecificneedsofastudioaudiosystem,ratherthan

generalizedInternetdatatraffic.Forthisreasonaswellasforobvioussecuritypurposesitis

importanttouseaseparate,dedicatednetwork(eitherphysicalorvirtual)forallstudioaudioIP

applications.Thisnetworkcancarryallaudiocontent,controlsignalsandmetadatarelatedto

production,butshouldbeisolatedfromthegeneraldatanetworkofthefacility.Inaddition,there

generallyshouldnotbeadirectconnectionofthestudioaudiosystemtothepublicInternet.When

Internetconnectionsarerequiredforaccesstooffsiteaudiosourcesordestinations,theyshouldbe

routedthroughaproxyserverorotherisolatingpath.SomevendorswillalsosetIPpacketprioritization

atahigherlevelforaudiocontentpacketsthanforgeneralnetworkdata.ThishelpsIPAudio

performanceevenonnetworksthatarenotdedicatedtoIPAudiousageonly.

Anotherissueisasimpleoneofconnectorstandards.SinceIPAudiogenerallytravelsonCAT5orbetter9

Ethernetcables,

the

RJ45

connector

is

used

for

all

terminations.

But

some

IP

Audio

system

implementersalsouseRJ45foranalogorAES3digitalaudioI/Oandpatching.Whilethiscanminimize

thenumberofdifferentconnectortypesusedinafacility,andreducethephysicalspacerequiredfor

connectorpanels,thereisnostandardfortheconfigurationofanRJ45connectorforthispurpose.So

individualIPAudioimplementershavedesignedtheirownunilateralformats,againpossiblylimiting

broadcasterstotheuseofonlycertainmanufacturersproductsinanIPAudiofacility,orrequiringthe

useofadapters.

Ofcourse,theneedtoretaincompatibilitywithanalogandAES3digitalaudiowilllikelyremainforsome

timeto

come

at

any

IP

based

audio

facility.

At

the

very

least,

live

microphone

signals

will

need

to

be

convertedfromtheirnativeanalogaudio(orinsomecases,perhapsAES3)format,andinsomecases

analogordigitalaudiofromotherdevicesorremotesourceswillalsohavetobeaccommodated.How

thisconversionprocessisaccomplishedisakeyfactorinthedesignofanIPAudiosystem.

Forthetimebeingatleast,theaboveoptimizationprocessesarguefortheselectionofasinglevendor

forthesupplyofIPAudioequipmenttoagivenbroadcastfacility,oratleasttheverificationthat

compatibilityamongdifferentvendorsIPAudioequipmentisassured.Workingwithasinglesupplier

alsoensuresthatupdatesandupgradeswillbedeliveredinatimelyfashion,andevenspecialfixesfora

particularproblem

encountered

at

agiven

facility

can

be

quickly

provided.

9CAT5eorCAT6



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ImplementationandintegrationThisbringsustoactualIPAudiosystemconsiderations.Giventheadvantagesofscaleprovidedbythese

systems,itmakessensetomaketheIPAudiodomainaslargeaspossiblewithinagivenfacility.That

impliesthataudiosignalsinotherformsshouldbeconvertedtoIPpacketsassoonaspossible.

Thebestplacetodothisinmoststudioconfigurationsisatthecentralpatchbayand/orthestudio

mixing

console(s).

Microphone

outputs

and

signals

from

other

legacy

audio

sources

can

be

immediatelyconvertedtodigitalaudioform(iftheyarentalready)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,essentiallyduplicatingtheappearanceandfunctionoftraditionalroutercontrolpanels.Inall

cases,however,allthatisbeingdonetoachievetheroutingistheadditionofappropriateIPaddresses

totheheadersofIPAudiopacketsonthenetwork.10

Ofcourse,themixingconsolecanalsobeequippedwithtraditionalanalog(mic/line)orAES3inputson

someinputsaswell,toaccommodatelocalaudiosourcedevices.Thesesourcesareinturnconvertedto

IPbytheconsole,andviatheirroutingtotheconsolebusordirectoutputs,thesesignalsmayinturnbe

madeavailableasIPsourcestotherestofthenetworkagainviathesinglecableconnectingthe

consoletothenetwork.(SeeFigure1.)

ConsideralsohowPCbasedaudioplayout/automationsystemscanbeinterfacedtosuchasystem.

RatherthantheiraudiooutputsbeingdirectedthroughPCsoundcardstotraditionalaudioinputs,the

automationsystemcanbefittedwithanIPdriverthatprovidesasoftwareinterfacebetweenthePC

audioandtheIPnetworkdirectlyintheIPAudiodomain.Thisnotonlymaintainshighaudioquality,but

cutscostsintheautomationsystemsinceno(oratleastfewer)soundcardsarerequired.TheIP

interfacecanalsocarrycontroldataandPADaswell,eliminatingtheneedforseparatedatalinks

betweendevices.

10Ideally,theIPfeedsto/fromanymixingconsoleinanIPAudiosystemareusedonlyforthoseitemsthatneed

accesstotheconsolesaudiomanipulationfeatures.Simpleinputtooutputconnectionscanbehandledbythe

coreIPAudioarchitecturewithouttakingupconsoleresources(orevenusingupacrosspoint,intraditional

switchingterms).TheconsolecanbeconsideredasanIPapplianceoraudioengine,whichcanhostanysortof

audioleveladjustment,mixing,processingorcoding/transcoding thatthefacilityrequires,applyingallsuch

processesefficientlyandwithintheIPdomain.



10/14

Moreover,asingleIPdriverinterfacebetweenanautomationsystemandanIProutingarchitecturecan

carrymanyindependentaudiochannels(perhapsupto24),whereasatraditionalswitchingsystem

wouldrequireacrosspoint(pluswiring)foreachsoundcardinputandoutput.Thecombinedhardware

savings(soundcards+crosspoints+wire+installation)inalargefacilitycouldbesubstantial.

AnyIPAudiosystemtodaywillalsoincludeoneormorestandardEthernetswitches,whichareusedto

interconnecttheEthernetconnectionsfromeachfacilityordevicethatprovidesaudioI/OviaIP.These

switchesarestandardtelecomdevices,whichreplacethemorecommonEthernethubsorroutersused

forsimilarRJ45terminationsintypicalhomeorsmallofficesituations.SwitchesarepreferredinIP

Audioapplicationsbecausetheyhavemoreintelligencethanhubs,whichallowsthemtoinspectdata

packetstodeterminetheirsourceanddestination,andforwardthemappropriately.Throughthis

intelligentcontrol,eachmessageisonlysenttotheintendeddevice,therebyconservingnetwork

bandwidthandprovidingbetterperformance(includingreducedlatency).

Figure1:ConceptualblockdiagramofatypicalIPAudiobasedbroadcaststudiofacility,showingonestudioandTechnicalOperationsCenter(TOC).

Ethernetswitchescomeinunmanagedormanagedforms,thelatterallowinguserconfigurationof

variousparametersoftheswitchsoperation.InsmallerIPAudiofacilities,unmanagedswitchescan

performadequately,whilelargerfacilitiesmaybenefitfrommanagedswitches.Someswitchesalso

TOC

Local

Audio

Sources

(Mic/line

Analogor

AES3)

Softwareinterface

(audio

+

control)

IPAudio

Converter

IncomingRemoteAudio+

ControlSignals

ProgramOutput

toAudio

Processors,

ConventionalSTL

Monitoring,etc.(AES3orAnalog)

To/from Interne

RadioServersLANorWAN

Ethernet

Switch

(Core)

PCbasedAudio

Storage/automation

System

(w/IPDriverSoftware)

EthernetSwitch(Edge)

Conversion

toIP

IPbasedMixing

Console

Ethernet

LAN

To/fromIPSTLs&

OtherSitesWAN

Ethernet

LAN

To/fromOther

Studiosinthe

Facility

LAN

STUDIO


TOC

Local

Audio

Sources

(Mic/line

Analogor

AES3)

Softwareinterface(audio+control)

IPAudio

Converter

IncomingRemoteAudio+

ControlSignals

ProgramOutputs

toAudio

Processors,

Conventional STLs,

Monitoring,etc.(AES3orAnalog)

To/from Internet

RadioServersLANorWAN

Ethernet

Switch

(Core)

PCbasedAudio

Storage/automation

System

(w/IPDriverSoftware)

EthernetSwitch(Edge)

Conversion

toIP

IPbasedMixing

Console

Ethernet

LAN

To/fromIPSTLs&

OtherSitesWAN

Ethernet

LAN

To/fromOther

Studiosinthe

Facility

LAN

STUDIO


11/14

includeremoteadministrationcapability.TodaysfastestswitchesoperateatGigabitspeeds,usingCAT6

cable,andthesearethemostappropriateforlowlatencyIPAudioapplications.

AsFigure1indicates,atypicalIPAudiofacilityincludesmultipleswitches,usuallyarrangedwithone

large(core)switchinacentralroom,andsmaller(edge)switchesplacedasneededinotherrooms

aroundthefacility.Suchdistributedroutingintelligenceimprovesperformance,andalsoprovides

redundancyincaseofswitchfailure.

NotealsothattheproliferationofVoIPandotherrealtimeapplicationsviaIPhavespawnedbroad

implementationofnonblockingarchitectureinrecentEthernetswitches.Thisapproachvirtually

eliminatesdatacollisionswithinaswitch,whilemaintainingcosteffectiveness,byensuringjust

adequatecapacityfornxnconnectivity11

throughtheswitchingfabric.Missioncriticalperformanceis

therebymaintainedbyusingEthernetswitchesthatimplementnonblockingdesign,andwhenproperly

implementedwithinanIPAudiosystem,switchcapacityshouldneverbeexceeded.MostIPAudio

vendorsrecommendonlynonblockingEthernetswitches,andthisisonereasonwhyusersshouldheed

vendorsrecommendationsforallswitchesusedintheirfacilities.(Again,theeconomyofscaledriven

bybroad

uptake

of

these

switches

today

provides

such

advantages

to

IP

Audio

implementers

at

very

attractiveprices.)

TheuseofEthernetswitchesbymissioncriticalandotherhighreliabilitytelecomoperationshasdriven

majormanufacturerstoprovideexcellent24x7andovernightreplacementsupport.Notealsothatasa

facilitygrows,itmayneedtoreplaceolderswitcheswithnewermodels;thefactthatEthernetisa

ubiquitousstandardmeansthatallupgradeswillremainbackwardcompatible.Meanwhile,Moores

Lawensuresthatassuchnewhardwarebecomesavailable,price/performanceratioswillcontinually

improve.

TheIPAudiodomainisalsoextendingbeyondthestudio.Figure1showshowIPAudioisconvertedback

toAES3(orevenanalog)forprogramoutputsconnectiontoconventionalStudiotoTransmitterLinks

(STLs),butthediagramalsoindicatesthatanSTLcouldcarryIPAudiotothetransmittersite(viaWANor

otherdedicatedlink).WhetherleasedfromtelcoorusingastationoperatedRFpath,ifadequate

bandwidthisavailable,multipleaudiochannels,controlandmetadatacanallbecarriedviaIPonthe

linkbidirectionally,ifdesiredwithminimallatency.12

IPAudioinUseTodayTheadvantagesofIPAudiohavebeennoticedbybroadcastersandstudioownersaroundtheworld.Itis

fairtosaythattheengineersdesigningeverynewbroadcaststudiofacilitybuilttoday(andfromthis

pointforward)areatleastconsideringtheuseofanIPAudioarchitectureandmanyofthemare

decidingtotaketheplunge.Speakingwiththemafterwardswillfindalmostunanimousagreementthat

11Inotherwords,anyinputontheswitchcanalwaysbeconnectedtoanyoutputontheswitch,underanyusage.

12BidirectionallinkscansubstantiallydecreasejitterandlatencycomparedwithunidirectionalIPpaths.



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itwastheproperchoice,andtheresnolookingback.Inmanycasesyouwillhearthatthetransition

processwasfareasierthantheyexpected.

TheinstallationofanIPAudiosystemmakesmanypeopleattheoperationhappy,fromtheCEtothe

CFO.ThetotalcostofbuildingandoperatinganIPAudiofacilityissignificantlyreduced,andyetthiscan

beaccomplishedwithoutgivingupflexibilityinfactit,too,isgreatlyincreased.Operationsareoften

minimallyinterrupted,aswell,duetothesmallfootprintandquickinstallationofIPAudiosystems.

Thisiswhybroadcastersofallstripes,andwithbudgetslargeandsmall,havemovedtoIPAudio

systems.OnthecommercialsideintheU.S.,broadcastersfromClearChanneltoGreaterMediahave

recentlyinstalledIPAudiosystems,whilenoncommercialoperatorsfromMinnesotaPublicRadioto

WYMS,Milwaukeehavedonethesame.

Infact,theclienteleforthisemergingtechnologyalmostdefiescharacterization.Itincludessmall

independentstations,collegeradio(includingnumerousruralandcommunitycolleges),ethnicand

religiousbroadcasters,satelliteradioservices,radioandtelecomnetworkoperators,contentproduction

andbroadcast

origination

sites,

corporate

facilities

and

government

agencies

along

with

some

of

the

largestandmostrespectedstationsinthecountry.

NeitherisadoptionisbyanymeanslimitedtotheU.S.IPAudioisalreadywellensconcedaroundthe

world,fromSpaintoSouthAfrica,fromItalytoIsrael,fromChinatotheCzechRepublic,andmanyother

placesinbetween.

Clearlythetechnologyhasalotofuniqueadvantagestooffer,andthesehavebeennoticedbymanyof

theleadingpurveyorsofaudiocontentanddeliverythroughouttheplanet.

ConclusionsItsnotoftenthatanewtechnologyoffersconsiderabletechnicalimprovement,easierinstallationand

maintenance,greatlyenhancedflexibilityandscalability,andreducedcostwhencomparedwithits

predecessors.YetthesearetheattributesofaproperlyimplementedIPAudiosystem.

Broadcastershavealwaysbeenacostconsciouslot,andrightlyso,butgiventodaysincreasingly

competitivelandscape,efficienciesincapitalexpendituresandoperatingcostshavebecomeevenmore

criticalanddesirable.

Meanwhile,itsbecomequiteclearthattheradioindustrywillfacesubstantialchangeinthenear

future,andmuchofitwilllikelyinvolvequantitativegrowthinservices.Morestreams,moreaudio

channels,moredata,moreresponsivenesstoaudiencedemands,andprobablymorestill,areallonthe

paththatliesaheadforbroadcasters.AnIPAudioplatformprovidesalegitimateplatformtomost

realisticallyaccommodatethesemanychallenges.



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ItbehoovesanybroadcasterfacedwiththeopportunitytoconfronttheseuncertaintiestoseekthecounselofexpertsinthefieldofIPAudio,andtobenefitfromtheexperienceofthosewhohaverecentlyundertakensimilarprojects.YouwilllikelyhearstrongencouragementtomakethemovetoIP,

justasmuchoftherestoftheworldisdoing,withgoodreason.Fairfax,VAFebruary2008



14/14

Axia Audio, a Telos Company 2101 Superior Ave. Cleveland, Ohio, 44114, USA +1.216.241.7225 www.AxiaAudio.com

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