通信专业文献及翻译基于JPEG技术融合DSP和FPGA的可纠错图像传输系统.docx

通信专业文献及翻译基于JPEG技术融合DSP和FPGA的可纠错图像传输系统.docx

《通信专业文献及翻译基于JPEG技术融合DSP和FPGA的可纠错图像传输系统.docx》由会员分享，可在线阅读，更多相关《通信专业文献及翻译基于JPEG技术融合DSP和FPGA的可纠错图像传输系统.docx（10页珍藏版）》请在冰豆网上搜索。

通信专业文献及翻译基于JPEG技术融合DSP和FPGA的可纠错图像传输系统

英文原文

MixedDSP/FPGAimplementationofanerror-resilientimagetransmissionsystembasedonJPEG2000

MarcoGrangetto,EnricoMagli,MaurizioMartina,FabrizioVacca

Abstract

Thispaperdescribesademonstratorofanerror-resilientimagecommunicationsystemoverwirelesspacketnetworks,basedonthenovelJPEG2000standard.Inparticular,thedecoderimplementationisaddressed,whichisthemostcriticaltaskintermsofcomplexityandpowerconsumption,inviewofuseonawirelessportableterminalforcellularapplications.ThesystemimplementationisbasedonamixedDSP/FPGAarchitecture,whichallowstoparallelizesomecomputationaltasks,thusleadingtoefficientsystemoperation.

1Introduction

Nowadays,thereisagrowinginterestintheend-to-endtransmissionofimages,especiallymotivatedbytheshort-termdeploymentofnextgenerationmobilecommunicationservices（UMTS-IMT2000）.However,transmissioninanetworked,tetherlessenvironmentprovidesbothopportunitiesandchallenges.Thewirelesscontextimpliesthatthedatamayundergobiterrorsandpacketlosses,makingitnecessarytoforeseeerrorrecoverymodalities.Itistherebynecessarythatimagecommunicationtechniquesareprovidedwiththeabilitytorecover,oratleastconceal,theeffectofsuchlosses.TheforthcomingJPEG2000imagecompressionstandardhasbeendesignedtomatchtheserequirements,andembedssomeerrordetectionandconcealmenttools.

Thispaperaddressesthedevelopmentofademonstratorofanerror-resilientJPEG2000decoderimplementationforimagecommunicationoveralossypacketnetwork.TherobustnesstopacketerasuresisachievedbycombiningtheflexibilityoftheJPEG2000frameworkwiththepowerfulnessofsource-channeladaptive,optimizedReed-Solomoncodes.Thedecoderimplementationisparticularlysignificantinthecontextofwirelessportableterminalsfornext-generationcellularsystems,wherethelimitedpowerbudgetandavailabledimensionsimposesevereconstraintsonthedesignofamultimediaprocessingsystem.

2Systemoverview

Inthefollowingweprovideabriefdescriptionofthefunctionalunitsoftheimplementedsystem.

2.1JPEG2000imagecompression

JPEG2000isthenovelISOstandardforstillimagecoding,andisintendedtoprovideinnovativesolutionsaccordingtothenewtrendsinmultimediatechnologies.Atthetimeofthiswriting,thestandardisinadvancedpublicationstage;theFinalCommitteeDraftisthemostrecentJPEG2000descriptionpubliclyavailable,whichourimplementationconformsto.JPEG2000notonlyyieldssuperiorperformancewithrespecttoexistingstandardsintermsofcompressioncapabilityandsubjectivequality,butalsonumerousadditionalfunctionalities,suchaslosslessandlossycompression,progressivetransmission,anderrorresilience.ThearchitectureoftheJPEG2000isbasedonthetransformcodingapproach.Animagemaybedividedintoseveralsub-images（tiles）,toreducememoryandcomputingrequirements.Abiorthogonaldiscretewavelettransform（DWT）isfirstappliedtoeachtile,whoseoutputisaseriesofversionsofthetileatdifferentresolutionlevels（subbands）;then,thetransformcoefficientsarequantized,independentlyforeachsubband,withanembeddeddead-zonequantizer.Eachsubbandofthewaveletdecompositionisdividedintorectangularblocks（code-blocks）,whicharein-dependentlyencodedwithEBCOT（EmbeddedBlockCodingwithOptimizedTruncation）;thislatterisbasedonabit-planeapproach（i.e.themostsignificantbitsofthesubbandcoefficientsaretransmittedfirst）,contextmodelingandarithmeticcoding.ThebitstreamoutputbyEBCOTisorganizedbytherateallocatorintoasequenceoflayers,eachlayercontainingcontributionsfromeachcode-block;thetruncationpointsassociatedwitheachlayerareoptimizedintheratedistortionsense.ThefinalJPEG2000bitstreamconsistsofamainheader,followedbyoneormoresectionscorrespondingtoindividualtiles.Eachtilecomprisesatileheaderandalayeredrepresentationoftheincludedcode-blocks,organizedintopackets.Inordertoformaprogressivebitstream,i.e.onethatcanbeonlypartiallydecodedwithminimalpenalty,thelayersareformedandorderedinsuchawaythatthemostimportantinformationisplacedatthebeginningofthebitstream.TheJPEG2000decoderperformsexactlythesamesteps（exceptforrateallocation）,inreverseorder:

syntaxparsing,codeblockdecodingbyEBCOT,inversequantization,inverseDWT,andtilemosaicking;thisissketchedintheright-hand-sideboxofFig.1.

2.2AdaptiveReed-Solomonpacketprotection

AlthoughJPEG2000embodiesadvancederrorconcealmenttechniquestomitigatetheeffectoferrors,itdoesneithercontain,norspecifyanyerrorcorrectionmethod,inordertorecoverlostpackets.Ontheotherhand,packetlossesarelikelytooccurinanetworkpotentiallysubjecttocongestion,asisoftenthecaseinpractice.Inordertoovercomethisproblem,atechniquehasbeenrecentlyproposed,calledUnequalLossProtection（ULP）,andbasedonthejointuseofRScodesandpacketinterleaving,asshownintheleft-hand-sideofFig.1.Letusconsideramaximumrateallocatedtotheimagetransmission,e.g.NpacketsofsizeL;thesourcebitstreamisrowwiseinsertedintheinterleavingmatrix,followedbyaproperamountofparitysymbols,sayTiforthei-throw.Thepacketsarereadonthecolumnsoftheinterleaver.Theallocationproblemconsistsinfindingtheoptimalpartitioningbetweensourceandcodesymbolsforeachrowoftheinterleaver,soastomaximizethequalityofserviceatthereceiver;seeforimplementationdetails.Atthedecoder,duetotheerrorcorrectioncapabilityofRScodes,thei-throwcanbeexactlyrecoveredprovidedthatthenumberofpacketerasureshasbeenlessthanTi.

Figure1Systemarchitecture

2.3Proposedsystem

Inthispaperwepresentademonstratorofacompletedecoderforimagecommunicationoveralossypacketnetwork.Thedecoderconsistsof1）ULPdecoder,followedby2）JPEG2000decoder.ThegoalistodemonstratethatsuchtaskscanbeeffectivelyperformedonamodernDSP,satisfyingreal-timeoperationrequirements.ThisobjectivehasbeenaccomplishedbyusingamixedDSP/FPGAarchitecture.Inparticular,theimplementationhasbeendevelopedusingaTexasInstruments（TI）TMS320C6201DSPboardastargetdevice.Theadditionalbitstreamprotectionprotocol,basedonRScodes,hasbeenimplementedonaVirtexXCVl000FPGAdevicefromXILINX,whichisabletoconcurrentlyexchangedatawiththeDSP.AsisshowninSect.4,thedevelopedsystemisabletoperformveryfastdecodingofstillimages,ataratecompatiblewithreal-timevideoapplications;thus,anextensiontoMotionJPEG2000videocodingcanbeenvisaged,withminormodificationsofthecurrentdemonstrator.

3Systemarchitecture

ResortingtomixedDSP/FPGAbasedarchitecturesallowstoachievevery-highperformancesystems,withexcellentpropertiesofreconfigurability.PreliminarypartitioningstudieshaveputintoevidencethatwavelettransformandEBCOTarethemostdemandingtasksinJPEG2000decodingprocess.However,sincemanyextensionsofthestandardarestillpossible,anall-DSPimplementationoffersanexcellentdegreeofreconfigurability.Ontheotherhand,FPGAiswellsuitedtotheimplementationofaReedSolomoncore,neededtogranterrorresilienceofthecommunicationsystem.Itisworthnoticingthat,withanULP,theRSdecoderneedstobere-adaptedtoworkwithwordsofbitswhichcankeepdifferentamountsofinformationsymbolsand,asaconsequence,differentamountsofprotectionsymbols.Theneedforchangingtheseparameters"on-the-fly"isperfectlyfulfilledbyanFPGA,bysimplyloadingnewvaluesintosomeconfigurationregisters.Moreover,thehighmemorybandwidthneededtoquicklyde-packetizeandde-codethereceivedbitstreammakestheuseofaReedSolomonFPGAimplementationveryattractive.TheJPEG2000decodermodule,entirelyimplementedonDSP,iscomposedbyfourmainblocks:

syntaxparser,entropydecoder（EBCOT）,uniformscalardequantizer,andinversewavelettransform.Moreover,twoadditionaltasks,devotedtocommunicationmanagementbetweenDSP,FPGAandapersonalcomputer,havebeenintroduced.

3.1Syntaxparser

TheparseristhefunctionalblockthatinterfacestheJPEG2000decoderwiththeRSdecoder.ItretrievesRSdecodedpackets,andextractsfromthecompressedJPEG2000bitstreamalltherelevantinformationneededtoperformimagereconstruction.Firstly,thebitstreammainheaderisread,whichcontainsinformationontheparametersusedduringtheencodingprocess（e.g.imagesize,waveletfilterused,numberofdecompositionlevels,quantizationthresholds,andsoon）.Afterthat,tileheadersareread,whichprovideinformationspecifictoeachimagetile.Finally,eachpacketcontainedinthebitstreamisread,andthedataandparametersofeachcodeblockareextracted,andfedasinputstotheEBCOTdecoder.

3.2EBCOT

Rightafterthebitstreamsyntaxparser,thesubsequentstageintheJPEG2000decompressionchainistheentropydecoder（EBCOT）.Fromanalgorithmicpointofview,EBCOTisablock-basedbitplaneencoderfollowedbyareducedcomplexityarithmeticcoder（MQ）.Itsubdivideseachwaveletsubbandintoadisjointsetofrectangularblocks,calledcode-blocks.Thenthecompressionalgorithmisindependentlyappliedtoeverycode-block.Thesamplesofeverycodeblockarearrangedintoso-calledbitplanes.Todecodeacode-block,EBCOTalwaysstartsfromthemostsignificantbitplanes,andthenmovestowardstheleastsignificantones.Thecompressedinformationofeverycode-blockisth