Video codec method in error resilient mode and app.docx

Video codec method in error resilient mode and app.docx

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Videocodecmethodinerrorresilientmodeandapp

Videocodecmethodinerrorresilientmodeandapparatustherefor

BACKGROUNDOFTHEINVENTION

1.FieldoftheInvention

Thepresentinventionrelatestoavideocoding-decoding（CODEC）methodandanapparatustherefor,andmoreparticularly,toavideoCODECmethodinanerrorresilientmodeandanapparatustherefor.Also,thepresentapplicationisbasedonUSProvisionalPatentApplicationNo.60/067,013,entitled“VideoCODECMethodinErrorResilientMode”,bythepresentapplicant.

2.DescriptionoftheRelatedArt

Ingeneral,incasethatanerrorexistsinachannel,videoCODECcannotcopewitherrorofthechannelwhenencodingallframesintobitstreams.Thisisbecausethebitstreamshavenodecisionelementfordeterminationofwhetherstreamshavenodecisionelementfordeterminationofwhethertorestoreordiscardtheerrorregion.Thus,itisdifficulttodeterminewhetheracertainportionofaframehasbitlossbyanerror,orwhethertheentireframehasanerror,sothatthereisaproblemthatastartpointofthebitstreamshouldbesearchedinthenextframe,ignoringthecodedbitstreamoftheentireframe.InaconventionalCODEC,anadditionaldeviceisusedasthedecisionelementinordertosolvesuchproblem.Asanexample,accordingtotheCODECdefinedintheH.263standard,apicturestartcode（PSC）isemployedandifanerrorisdetectedafterthisfieldinformation,theregionfollowingthePSCisignoredandthenextPSCisthensearched.Further,agroupofblockstartcode（GBSC）indicatingthestartofthegroupofblock（GOB）isemployedandifanerrorisdetectedafterthisinformation,onlythecorrespondingblockoftheGBSCisignoredandthenthenextGOBissearched,therebyreducingtheamountoftheignoredregion.

FIG.1showsanexampleofavideodatapacketgeneratedbyaconventionalCODECinanerrorresilientmode.ThevideodatapacketofFIG.1isanexampleofthevideodatapacketgeneratedintheMPEG-4CODEC.Referringtothispacket,intheconventionalerrorresilientCODEC,dataisdividedintomotiondataandtexturedataforcoding.Themotiondataconsistsofamacroblockidentificationbit（COD）indicatingwhetherornotcodingisperformed,amacroblockpatternchrominance（MCBPC）bitindicatingthechrominanceofeachmacroblockandamotionvector,andthetexturedataconsistsofcodedblockpatternluminance（CBPY）data,dataquantization（DQUANT）dataanddiscretecosinetransform（DCT）data.Suchmotiondataandtexturedataaredividedbyamotionmarker（MM）.Also,theDCTdataiscodedbyreversiblevariablelengthcoding（RVLC）.

Thedecodingprocessofthebitstreamcodedintheabovemannerwillbedescribed.First,aresyncmarkerRMissearchedinthebitstream.IfanRMisfound,informationuptothenextRMisregardedasonepacket.Amotionvectordatapart（MVDP）consistingofmotionvectorshasonlypredictedmotionvectors,sothatitispossibletouseanactualmotionvectoronlywhenthepreviouslydecodedmotionvectorexists.Thus,ifanerrorisdetectedfromtheMVDPofthebitstream,thecorrespondingentirepacketisignored,andanRMcorrespondingtothenextpacketissearchedfordecoding,therebycausinglossofalargeamountofinformation.

SUMMARYOFTHEINVENTION

Tosolvetheaboveproblems,itisafirstobjectofthepresentinventiontoprovideavideocoding-decoding（CODEC）methodinanerrorresilientmode.

ItisasecondobjectofthepresentinventiontoprovideacomputerreadablemediahavingembodiedthereonacomputerprogramforthevideoCODECmethodinanerrorresilientmode.

ItisathirdobjectofthepresentinventiontoprovideavideoCODECapparatusinanerrorresilientmode,achievingthevideoCODECmethod.

Accordingly,toachievetheabovefirstobject,thereisprovidedavideoCODECcomprisingthestepsof:

（a）partitioningaheaderdatapart（HDP）bitregion,amotionvectordatapart（MVDP）bitregionandadiscretecosinetransformdatapart（DDP）bitregionfromeachmacroblockofthevideodatainanerrorresilientmode;（b）variable-length-codingthepartitionedbitregions;（c）reversible-variable-length-codingthebitregionsselectedfromthevariable-lengthcodedbitregionsaccordingtoapredeterminedpriorityforrecovery;and（d）insertingmarkersintothevariable-lengthcodedorreversible-variable-length-codedbitregions.

Toachievethesecondobject,thereisprovidedacomputerreadablemediumhavingembodiedthereonacomputerprogramforexecutingthevideoCODECmethodwhichcomprisesthestepsof:

（a）partitioningaheaderdatapart（HDP）bitregion,amotionvectordatapart（MVDP）bitregionandadiscretecosinetransformdatapart（DDP）bitregionfromeachmacroblockofthevideodatainanerrorresilientmode;（b）variable-length-codingthepartitionedbitregions;（c）reversible-variable-length-codingthebitregionsselectedfromthevariable-lengthcodedbitregionsaccordingtoapredeterminedpriorityforrecovery;and（d）insertingmarkersintothevariable-lengthcodedorreversible-variable-length-codedbitregions.

Toachievethethirdobject,thereisprovidedavideoCODECapparatuscomprising:

apartitioningunitforpartitioningaheaderdatapart（HDP）bitregion,amotionvectordatapart（MVDP）bitregionandadiscretecosinetransformdatapart（DDP）bitregionfromeachmacroblockofthevideodatainanerrorresilientmode;avariablelengthcodingunitforvariable-length-codingthepartitionedbitregions;areversiblevariablelengthcodingunitforreversible-variable-length-codingthebitregionsselectedfromthevariable-lengthcodedbitregionsaccordingtoapredeterminedpriorityforrecovery;andamarkerinsertingunitforinsertingmarkersintothevariable-lengthcodedorreversible-variable-length-codedbitregions.

BRIEFDESCRIPTIONOFTHEDRAWINGS

Theaboveobjectsandadvantagesofthepresentinventionwillbecomemoreapparentbydescribingindetailpreferredembodimentsthereofwithreferencetotheattacheddrawingsinwhich:

FIG.1showsanexampleofavideodatapacketgeneratedduringconventionalcoding-decoding（CODEC）inanerrorresilientmode;

FIG.2isaflowchartillustratingthemainstepsofavideoCODECmethodinanerrorresilientmodeaccordingtoapreferredembodimentofthepresentinvention;

FIG.3isablockdiagramofavideoCODECapparatusinanerrorresilientmodeaccordingtoapreferredembodimentofthepresentinvention;

FIG.4showsanexampleofavideodatapacketgeneratedbytheerrorresilientvideoCODECmethodaccordingtothepresentinvention;

FIG.5isaflowchartillustratingthestepsofadecodingmethodofavideoCODEC;and

FIG.6isaflowchartillustratinginmoredetailthedecodingstepoftheflowchartofFIG.5.

DESCRIPTIONOFTHEPREFERREDEMBODIMENTS

ReferringtoFIG.2,whereinthemainstepsofavideocoding-decoding（CODEC）methodinanerrorresilientmodeaccordingtoapreferredembodimentofthepresentinventionareillustrated,thevideoCODECmethodincludesapartitioningstep20,avariablelengthcodingstep22,areversiblevariablelengthcodingstep24performedforselectedbitregions,andamarkerinsertingstep26.

Inthestep20,aheaderdatapart（HDP）bitregionisconstitutedbypartitioningheaderdata.Inasimilarmanner,amotionvectordatapart（MVDP）bitregionandadiscretecosinetransform（DCT）datapart（DDP）bitregionareconstitutedbypartitioningmotionvectordataandDCTdata,respectively.

Theheaderdataincludesinformationaboutcodingstatusofthecurrentmacroblock.Thatis,theheaderdatarepresentswhetherthecurrentmacroblockisanintramacroblockinwhichthecontentofthecurrentframeiscodedasitis,oranintermacroblockinwhichthedifferencefromapreviousmacroblockiscoded.Thus,ifanerroroccursinthedeaderdata,verycriticalinformationlosswouldbecaused.

Thus,duetothesignificanceoftheheaderdata,theheaderdatamustberecoveredfirst.Forthisreason,amongtheHDP,amacroblockidentificationbit（COD）indicatingwhethercodingisperformedornotandamacroblockpatternchrominance（MCBPC）bitmaybecombinedintoonenewsyntax（COD+MCBPC）forpartitioning.Thiscombinationforpartitioningispreferredduetothefollowingreasons.IntheH.263standard,1bitisusedfortheCODbitandavariablelengthcodeisusedfortheMCBPCbitoftheheaderdata.However,becausetheCODbitcanhaveboth0and1,itisdifficulttodetectthattheCODbithasanerror.Also,incasethattheMCBPCbitusingavariablelengthcodetablehasanerror,itisverylikelythattheerroneousbitexistsinavariablelengthcodetable,sothatthedetectingtheerrorisdifficult.Thus,inthisembodiment,theCODbitandtheMCBPCbitarecombinedforpartitioning,andthecombinedbitregionisreversible-variable-length-coded,therebyeasilydetectingthechangeinthebit.Forexample,inthecaseofdata0110,anerrorsuchas0101or1001canbedetected,sothatthepossibilityofusingtheerroneousinformationisreduced.Further,becausethereversiblevariablelengthcodingisperformed,backwardrecoveryisalsopossible.However,theHDPregionmaybeconstitutedthroughpartitioningwithoutacombinationofbits.

Also,thestep20isperformedinmacroblockunitssothatitispreferredtoincludethestepofinsertingafirstmacroblockindex（FMBI）bitregionindicatingtheserialnumberofthefirstmacroblockintoeachpacket,whichcanbereferredtofordecoding.Also,preferably,thestep20includesthestepofinsertingalastabsolutemotionvector（LAMV）bitincludingabsolutemotionvectorinformation,notapredi