Video codec method in error resilient mode and app.docx
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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
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