JBL VT4880ADP User Manual - page 34
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User’s Guide
APPENDIxA:CONFIGURINGCOBRANET
General
CobraNetisalicensedtechnologydevelopedbyPeakAudio,Inc.consistingofproprietarycommunications
protocol,firmwareandhardware.Itallowsreliable,deterministic(i.e.real-time)transmissionofhighquality
(i.e.un-compressed)digitalaudiooverstandard100Base-TFast-Ethernetnetwork.CobraNetwillalsooper-
ateonfasterversionsofEthernet(e.g.Giga-bitand10Giga-bit).
ACobraNetsystemiscomprisedofCobraNetdevicesandtheEthernetnetworkthatconnectsthem.PCsor
othersystemcontrollersmayalsobeconnectedtothenetworkforsetupbutarenotrequiredforoperation.
Ethernet
EthernetisahardwareandsignalingspecificationdevelopedbyXeroxin1970fordatanetworking.TheIEEE
(InstituteofElectricalandElectronicsEngineers)standardizedthetechnologyintheIEEE80.standard
anditsvariants.
Withover50millionnodesinstalled,Ethernetiseasilythemostdominantdatanetworkingtechnologyinuse
today.ItiscarriedoverinexpensiveCAT-5UTPcablesorfiber.TypicalEthernetcablinglimitationsare:100
metersoverCAT-5coppercable,kilometersovermultimodefiber.
TheCobraNet™Device
EachCobraNetdeviceembedsspecializedhardwareandfirmware.Thehardwareincludesastandard
100MBFast-Ethernetinterfacealongwithcustomhigh-speedDSPchipsandclockcircuitry.TheDSPand
itsembeddedsoftwareareusedtoencodeanddecodetheEthernetnetworkmessagesusingthepropri-
etaryprotocol.Theclockcircuitryisusedtoaccuratelydecodethesystemmasterclocktimingneededfor
high-qualityreal-timeaudiodelivery.
AudioSpecs
AllCobraNetdevicesoperateatafixedsamplerateof8kHz.Theaudiodatamaybetransmittedat16,0
orbitdataasdesired.Forreliableoperation,eachCobraNetdevicemustimplementtransmitandreceive
buffering.Thisbufferingisfixedat56samplesandresultsinaminimumaudionetworklatencyof5.ms.
(56samplesat1/8kHzpersample)
BundlesandAudioChannels
RoutingofdigitalaudiobetweenCobraNetdevicesisaccomplishedthroughBundles.ABundleisthename
giventotheproprietaryencodedmessage(a.k.a.“packet”)transmittedbetweenCobraNetdevicesthatin-
cludemultiplechannelsofdigitalaudio.EachCobraNetdevicecantransmitandreceiveuptofourBundles.
EachBundleincludesupto8AudioChannels.Therefore,eachdeviceiscapableoftransmittingandreceiv-
inguptoAudioChannelstoandfromthenetwork.
BundlescanbetransmittedusingEthernetmulticastorEthernetunicastmethods.MulticastBundlesare
senttoallCobraNetdevicesonthenetwork,whileunicastBundlesaresenttooneandonlyoneCobraNet
device.SinceeachdevicecansendandreceivefourBundles,greatflexibilityisallowedintheroutingof
audiooverthenetwork.Upto8multicastBundles(6AudioChannels)canbetransmittedonasimplere-
peaterbasedEthernetnetwork.UptomulticastBundles(AudioChannels)alongwithupto1unicast
Bundles(>000AudioChannels)canbetransmittedsimultaneouslyonafull-duplexswitch-basedCobraNet
network.
AssignmentofBundlesisaccomplishedthroughtheselectionofaBundlenumber.Bundlesbetween1-55
arealwaysmulticast,whileBundlesbetween56-65,79areunicast.Bundleassignmentsmustnotbe
duplicated.OnlyoneCobraNettransmitterisallowedperbundle.
TheConductor
OnaCobraNetnetwork,theConductorcoordinatestransmissionofaudiopacketsthroughouttheentire
network.WhentwoormoreCobraNetdevicesareinterconnectedproperly,oneofthemwillbeselectedthe
ConductorbasedontheirrespectiveConductor.