現(xiàn)代音頻編碼的濾波器組設計與實現(xiàn).pdf

1、東南大學碩士學位論文現(xiàn)代音頻編碼的濾波器組設計與實現(xiàn)姓名：GEGEOMANETWUMASI申請學位級別：碩士專業(yè)：無線電工程指導教師：吳真陽2002.4.1、ABSTRACTAllaudiocodecsrelyonsometypeoftime—frequencyanalysisblocktOextractfromthetime—domaininputasetofparametersthatisamenabletoquantization

2、，anddecodinginaccordancewithperceptualmetricsThetoolcommonlyusedforthismappingisthefilterbank，aparallelbankofbandpassfilterscoveringtheentirespectrumThefilterbankdividesthesignalspectrumintofrequencysubbandsandgeneratesa

3、timeindexedseriesofcoefficientsrepresentingthefrequencylocalizedsignalpowerwitheachbandByprovidingexplicitinformationaboutthedistributionofsignalandhencemaskingpoweroverthetimefrequencyplane，thefilterbankplaysanessential

4、roleintheidentificationofperceptualirrelevancieswhenusedinconjunctionwithaperceptualmodelThefilterbankfacilitatespsychoacoustieanalysisaswellasperceptualnoiseshapingOntheotherhandbydecomposingthesignalintoitsconstituentf

5、requencycomponentthefilterbankalsoassistsinthereductionofstatisticalredundanciesThechoiceofanappropriatefilterbankiscriticaltothe∞c∞ssofaperceptualaudiocoderEfficientcodingperformancedependsheavilyonadequatelymatchingthe

6、propertiesofthemudysisfilterhanktothecharacteristicsoftheinputsignalIndesigningallalgorithmtheremustbeabalance／compromisebetweentimeandfrequencyresolutionwhenselectingafilterbankstmetareSincefailuretochooseasuitablefilte

7、rbankcanresultinperceptualartifactsintheoutput(egPreechoes)orimpracticallylowcodinggainandattendedhighbitratesAsaresultafilterbankusedfordigitalaudiocodingmusthavethefollowingproperties：(a)beeitheroftheperfectreconslruct

8、inntypeormustexhibitreconstructionerroBofaboutoI碡leastsignificantbit(LSB)ofanaudiosignal(1&bitwordlength)underworsecssecircumstances(b)Shouldkeepqunutizntion㈣r鵝constrainedinthefrequencydomain酗pessmle(ietheprototypefilter

9、shouldbenearlyofthebrickwalltype)(c)AfastalgorithmtocalculatethefilterbankisdesiredThisthesisthereforeconsidersthedesignandimplementationofModifiedDiscreteCosineTransform(MDCT)filterbankandPolyphasefilterbank也alcangnanmt

10、ennearperfectorDe成ctreconstruction眥TiSapem斌recommalctudcosinemodulatedfilterbankwithL烹2M，Thismeansthattheoutputisjustadelayversionoftheinputassumingnoquautization，thistypeoffilterisusedinColbyAC3，MPEG1layer3andMPEG2AACTh