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1、ABSTRACTABSTRACTAstheinternetbecomesuniversalinscopeandthetechnologydevelopsrapidlyinrecentyears,VoIPsystemhasdevelopedrapidlythroughouttheworldbyitscomparativelylowcostofspeechbusiness.SpeechcodingtechnologyisthekeytechnologyofVoIPsystemwhichdecidesitsperfo
2、rmancedirectly.Thestudyofspeechcodingtechnologyistoreducethebitrateandthetransmissionbandwidth,meanwhileaimstoensurecertainspeechqualityandthedelay.G.723.1speechcodingstandardisoneofthecodingstandardswhichiswidelyusedintheVoIPsystemwithitsgoodcomprehensivepe
3、rformance,thereforeitbecomesthestudyofthisdissertation.Inthevideophoneandvideoconferencesystems,ittakesmoretimetocodeanddecodespeechandimage,thatcausestheG.723.1speechcoderhaslargerdelay,anditcan'tbeusedinpractice,thereforetheefficiencyofG.723.1speechcoderal
4、gorithmicmustbeimproved.BecauseoftheproblemsofG.723.1codingstandard,thisdissertationcarriesoutmorein-depthresearchaboutit,andalsoproposessomeoptimizationandimprovementonthealgorithmic.Therearemainlytwoaspects:First,accordingtothefeatureofthesolutionoflinespe
5、ctralpairthatrequiresresearchingandcalculatingmanytimes,thedissertationproposesakindofoptimizationalgorithmwhichcanreducethenumberofresearchandthecomputingcomplexity,atthesametime,accordingtotheresultofsimulation,theoptimizedalgorithmcanincreasealevelofpreci
6、sionofthelinespectralpairwithitslowcomplexity.Second,thedissertationdiscussesthealgorithmicimprovementaboutthesearchalgorithmicoftheclosedlooppitchlag,proposesanewandfastsearchalgorithmicoftheclosedlooppitchlag.Comparingwiththestandardoftheresearchwhichsearc
7、hestheclosedlooppitchlagandthefifthorderpitchpredictorgainsatthesametime,theproposedalgorithmicisamethodtoresearchsequentially.Firstofall,usingthefirstorderpitchpredictorgainstofindtheclosedlooppitchlag,second,findthebestvectorquantizationcodebookofthepitchp
8、redictorbasedonthelagwhichhasbeenjustfound.TheresultoftheexperimentshowsthatthecomplexityII万方数据ABSTRACTlevelofthedevelopedalgorithmicreducedbyabout30%duringtheprocessofcoding.Althoughthequalityo
