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Implementing

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Implementing

    Implementing

    Zhuotal/JZhejiangUnivSciA20078(12:20052016

    JournalofZhejiangUniversitySCIENCEA

    ISSN1673-565X(Print);ISSN1862-1775(Online)

    wwwzjueducn~zus;wwwspringerlinkcom

    E-mail:jZUS@zjueduca

    ImplementingVLPRsystemsbasedonTMS320DM642

    ZHULeqing,ZHANGSanyuan,YEXiuzi

    (SchoolofComputerScienceandTechnology,ZhejiangUniversity,Hangzhou310027,China)

    E-maikzlq26@163.com

    ReceivedJan31,2007;revisionacceptedApr.6,2007

    2005

    Abstract:ThispapergivesapracticalschemaforusingDSPboardstoconstructVehicleLicensePlateRecognitionfVLPR)

    modulesthatcouldbeembeddedinanyIntelligentTransportationSystemrITS).UsingDSPcanavoidtheheavyinvestmentin

    dedicatedVLPRsystemandimprovethecomputationalpowercomparedtoPCsoftwareenvironment.Lowcost,highcomputa-

    tionalpower,andhighflexibilityofDSPprovidetheLicensePlateRecognitionSystemrLPRS)arlexcellentcost.effectivesolution

    toexecutethemajorpartoftherecognitiontasks.ThispaperdescribesasuccessfulimplementationofvLPRsystembasedon

    TexasInstruments(TI)'sTM$320DM642.TheDSPboardacquiresvideofwhichcouldbeoutputtoamonitorforsurveillance)

    fromacameracapturesimagesfromthevideo.1ocatesandrecognizesthelicenseplatesinimages.andthensendstherecognized

resultsandrelatedimagesaftercompressiontoahostPCthroughthenetwork.Finally,theover

    allsoftwareisoptimizedaccording

    tothefeaturesOfDM642chip.ExperimentsshowedthattheDSPVLPRsystemperforlTISw

    ellonthelocallicenseplates.andthat

    theprocessingspeedandaccuracycanmeettherequirementofpracticalapplications.

    Keywords:LicensePlateRecognition(LPR),Embeddedsystem,Imageprocessing,DSP,D

    M642

    doi:10.163l~zus.2007.A2005Documentcode:ACLCnumber:TP391.41 INTRODUCTION

    VehicleLicensePlateRecognitionfVLPR1isan

    importanttechnologywhichutilizescomputervision andpatternrecognitioninmodernInte1gentTrans.

    portationSystems(ITS).Thebasictechnologiesused inautomaticrecognitionsystemforvehiclelicense platesincludedigitalimageprocessing,patternrec

    ognitionandembeddedsystem.Avideocameratakes

    thepicturesofvehiclesrunningontheroadandthen

    thesystemanalyzesthepicturesandgivesoutthe

    recognitionresult.Inthisway-thesystemcanC0111. pletetheLicensePlateRecognition(LPR1automati. callywhilevehiclesarenotaffected.Thecomplexity oftransportationmanagementisdecreased,since

    VLPRtechnologycanbeusedinautomatictollco1.

    1ection,trafhccontrolandsurveillance.automatic vehiclesrecognition,automatichighway

    report,accesscontrol,automaticparking

    accident

    control,

    projectsupportedbytheNationalNaturalScienceFoundationof China(No.60473106),theHi-TechResearchandDevelopment

    Program(863)ofChina(Nos2007AA01Z311and2007AA04ZA5) vehicleslocation,vehicletheftsenforcement,and borderprotection,etc.(Anagnostopouloseta1.,2006) VLPRtechnologyisveryimportantinmaintaining cityandtrafficsecurity,avoidingtrafficiam,increas. 1ngserviceefficiencyoftransportationmanagement, andthusrelievingtraffictensioncomparatively. ReportedresearchesonLPRaremainlycon

    centratedontheprocessingstepssuchascarplate detection,extractionofalicenseplateregion,seg. mentationofcharactersfromtheplate.andrecogni. tionofeachcharacter.Anenhancedcascadedtree stylelearnerforcarplatedetectionwasproposedby Wueta1.(2006).Thealgorithmadoptsthehybrid objectfeatureswhichincludetwokindsofsimple statisticalfeatures.gradientdensityandgradient densityvariancewhicharebasedonverticalgradient oftheimage.andwel1.knownHarr.1ikefeatures.As forlicenseplateregionlocation.themethodsofcolor detection(ChoandJung,1998),signatureanalysis (Barrosoeta1.,1997),edgedetection(BaiandLiu, 2004)wereproposed.In(Choudhuryeta1.,2003), platecharacterregion'slocationiSidentifiedbytak.

Zhuetal/JZhejiangUnivSciA20078(12:2005-2016

    ingverticalcolorconcentrationintheimage.Sliding ConcenicWindows(SCWs)wereusedforfaster

    detectionofplateregionsin(Anagnostopouloseta1., 2006).Computingtechniquesrootedinfuzzytech

    niquewerealsoproposedin(Changeta1.,2004).Any

    tiltinthecapturedimageiscorrectedinthisstep.As forcharactersegmentation,thecharacter'sgraylevel bandsweredetectedtosplitcharacters.Character segmentationwasrealizedbytakinghorizontalcon

    centrationofcolorintheimagein(Choudhuryeta1.. 2003).ByusingLaplacianTransformation,region growingandpriorknowledge,thesegmentationwas moreaccurateandrobustthanthesimpleprojection (Yangeta1.,2006a).Andforcharacterrecognition, therearegeneticalgorithms(Kimeta1.,l996),arti

    ficialneuralnetworks(Bruggeeta1..1998;Parisiet a1.,1998;Kimeta1.,2000),fuzzyc-means(Nijhuiset a1.,1995),SupportVectorMachine(SVM)(Kimet a1.,2000),Markovprocesses(CuiandHuang,l997), andfiniteautomata(Adomietall998).SCW

    methodwasemployedforimagebinarizationin conjunctionwithaprobabilisticneuralnetwork(PNN) forcharacterrecognitionin(Anagnostopouloseta1., 2006).In(Chileta1.,2006),asimplemethodthat employsSVMforChineseLPRwasproposed.

    Characterrecognitionwasaccomplishedbymatching paRemsofhorizontalandverticalhistogramsin (Choudhuryeta1.,2003).Asforadaptationto changingenvironment,Naitoeta1.(2000)presenteda sensingsystemutilizingtwoCCDsandaprismto splitanincidentrayintotwolightswithdifferent intensitiestocoverwideilluminationconditionsfrom twilighttonoonundersunshine.

    Fig.1GeneralarchitectureoftheVehicleLicensePlate Recognition(VLPR1systembasedonDSPboard

    B=Board;M=Monitor;C:Camera;MO=MonitorObject ThispaperintroducesaVLPRschemebasedon TMS320DM642DSPandisorganizedasfollows. Section2givesageneraloverviewofthesystem structure.Section3introducesthehardwaredesignof thesystem.SoftwaredesignofDSPsystemandhost computeraregiveninSection4andSection5,re

    spectively.Experimentalresultsarepresentedin Section6,andfinally,conclusionsandfutureexten

    sionsarepresentedinSection7.

    SYSTEM0VERVIEW

    Thesystemincludesavideocamera.aDSP

    circuitboard,amonitorandapersonalcomputer servingasthehost.Thecameratakesthevideoof vehiclesrunningontheroad.Ananalogcomposite videosignalisreceivedthroughSportfromthe

    cameraanddecodedintoadigitalparallelBT656 stream:then,thestreamflowsintoDM642'svideo portwhichgetsimagebydecodingtheBT656stream, andtheresultingimageisstoredintoanSDRAM throughEnhancedDirectMemoryAccess(EDMA).

    Atiertheimageiscaptured.theDSPprocessesthe images.recognizesvehiclelicenseplatefromthe images,andfinallysendstherecognitionresultsand relatedimagesaftercompressiontothehostcomputer throughEthernetport.Thehostcomputerreceivesthe informationfromtheDSPboardsdisplaysthemon thescreenandsavestheinformationintothedatabase. Ausercanreviewtheresultsandrelatedimagesby accessingthedatabase.TheDSPboardalsohasan

RCAcompositevideooutputport.theusercancon

    necttheporttoavideomonitorandseewhatishap

    peningontheroad.

    Fig.1isanexampleOfVLPRapplicationbased onDSPboard.Thereare6DSPboardsinthissystem. WenameeveryDSPboardtogetherwiththecamera andthemonitorconnectedtoitasasubsystem.Each subsystemhandlesonevideostreamthatthecamera recordscontinuouslyofsomemonitoredobjectssuch asthestatusofahighwaylane.Theremaybe6or morelanesonahighway.Itisassumedthatthereare6 lanesonthehighwayhere.Iftherearemoreorless lanes,iustaddonorcutoffsomeDSPsubsystems.It wouldbeOKsincetheEthemetcouldbeextended flexiblywithincertainrange.TheDM642chiponthe boardprocessestheimageframes,recognizesthe licenseplate'stype.colorandnumbeLandusesJPEG algorithmtocompresstheimage.Then.ifthePC

    Zhuetal/JZhejiangUnivSciA2007a(12):2005-2o16 sendscommunicationrequirementtotheDSPboard, theresultandtheimageinthebufferwouldbe transmittedtothePCthroughtheEthernetimmedi

    ately.Thecapturedvideostreamisencodedand outputtothemonitorsimultaneously.

    HARDvvAREDESIGN

    ThecamerahasanSvideoporttooutputvideo

    signaltoDSPboardandthemonitorhasanRCAport toinputvideosignalfromDSPboard.ThekeyDartof thissystemistheDSPboard.Inthissectionwe

    mainlyintroducethecompositionorDSPcircuit boardwhosearchitectureisshowninFig.2. s-VideoJ]Composite

    lnIlin

    SDRAM

    Videodecoder

    SAA7115

    Emulation

    headers

    Composite

    out

    Videoencoder

    SAA7l05

    Fig.2GeneralarchitectureofDSP

    Thevideosignalinputfromthecameraissam

    pied.A/Dconverted.reorganizedandthensenttothe DSRwhichprocessestheimageframesofthevideo. tryingtodetermineifthereisalicenseplateinthe image;ifsotheDSPusesVLPRalgorithmtorec

    ognizethelicenseplate'stype.colorandnumber,and thenusesJPEGalgorithmtocompresstheimage. DSPcantransmittherecognizedresultandrelated compressedimagetothehostcomputerthroughthe Ethernet.Thehostcomputercancommunicatewith severalDSPsconcurrently,requireandacceptrecog

    nizedrestlltandrelatedimagesfromdifferentDSP boards.Atthesametime,thecapturedvideoisoutput toanencodertorestorethedigitalvideointoanalog datawhicharesenttothemonitorfordisplay.Since

    DSP'sonchipmemoryisnotenoughforthesoflware torun,andthewholesofiwareshouldbestoredina nonvolatilememorydevice.weinstalledSDRAMs andFlashfortheDSPthroughtheExternaMemor,/

    InterFacerEMIF).

    CorechipDM642

    TheTMS320DM642(DM642forshort)devel

    2007

    opedbyTexasInstrumentIncorporatedisanexcellent optionfordigitalmultimediaapplications.Itoffers cost..effectivesolutionstohigh..performanceDSP programmingchallengeswithupto5760MIPSata clockrateof720MHz.Itscoreprocessorhas64 generalpurposeregistersor32bitwordlengthand8

    highlyindependentfunctionalunits2multipliers

    f0ra32bitresultand6ALUs.TheDM642usesa twolevelcachebasedarchitectureandhasapower

    fulanddiversesetofperipherals.Italsohasa64bit

    seamlessEMIFwhichcaninterfacetosynchronous andasynchronousmemoriesandperipherals.The TM$320DM642DSPisIEEE1J49.IJAGBound

    aryScanCompatible.Inordertosupportmultimedia applications.theDM642devicehasbeenintegrated with3configurableVideoPortfVP0,VP1,andVP2) peripheralsandMultiChannelAudioSerialPort

    rMCASP).TheEthernetMediaAccessController rEMAOprovidesanefficientinterfacebetweenthe DM642DSPcoreprocessorandthenetwork.The DM642EMACsupportboth10BaseTand100Base

    TX.orl0Mbpsand100Mbpsineitherhalf-or

    fu11duplex,withhardwareflowcontrolandOoS supportfTl,2005).TheDM642EMACusesacustom interfacetotheDSPcorethatallowsef.ficientdata transmissionandreception.SinceDM642hasthe aboveadvantages.ourVLPRsystemiscoredwith DM642toaccomplishrealtimevideocapturing. imageprocessing,compressing,1nlormationtrans. mission,etc.

    Videoinputandoutputcircuit

    WeadoptedPhilipsSemiconductors'

    SAA7ll5Hasourvideodecoderdevice.Theanalog videosignalinputfromSvideoportorcomposite portisclamped.antialiasingfiltered,A/D.converted. YUVseparatedfLambers,2001),andthenchanged intodigitalparallelBT.656videostreamwhichiSin turnsenttocorechipDM642,whichhas3videoports VP0.VP1.andVP2.HereweuseVPOasthevideo inputporttoconnectwiththedecoderSAA7ll5H andVP2asthevideooutputporttoconnectwiththe encoder.VP0channelisconfiguredinto8bitBT.656

    inputvideoport.Thelineorfieldsvnchronization signalsareincludedintheEndofActiveVideofEA\,) andStartofActiveVideofSAV)timebasedsignalsor BT.656digitalvideoflow.Settinguptheparameters andreadingthestatutesofinternalregistersin FM

    E2

    MGTA

    V

Zhuetal/JZhejiangUnivSciA20078(12:20052016

    SAA7ll5HarecarriedonthroughI2Cbus.DM642 decodestheBT.656streamandgetstheimages. whicharestoredintotheSDRAMautomatically throughtheEDMAchanne1.

    DM642videooutputportgetsthedatafromthe SDRAMoutoutbufferthroughEDMAandfornls BT656stream.WeusePhilipsSemiconductors' SAA7105HtoencodetheBT656streamandturnit intostandardTVsigna1.Thesignaloutoutfromthe SAA7l05Hissenttothemonitorthroughcomposite port.

    Extendedmemory.

    circuit

    DM642has16kBLevel1fL1programcache,

    16kBL1datacacheand256kBLevel2rL2mem- pry/cachethatissharedbetweenprogramanddata spaceandcouldbeconfiguredasmappedmemory, cache.orcombinationofboth.Thatisnotenoughfor processingimage.Weextendedtwo32MBSDRAM (MT48LC4M32B2)chipstostoretheoriginalimage dataandan8MBFlash(AM29LV640MT)tostore applicationprogram,whicharemappedtotheexter- nalmemoryspaceCE0andCE1ofDM642.respec. tively.

    Ethernetinterfacecircuit

    ThesystemusesIntel'sLXT97lasthehigh speedEthernetphysicallayerself-adaptivetrans- ceiver.LXT97lsupportstheIEEE802.3standardand providesMediaIndependentInterface(MII).Italso

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