ITU-T J.51 (08 1994)(英) General principles and use

INTERNATIONALTELECOMMUNICATIONUNION)454*EX#-44 TELECOMMUNICATION(08/94)STANDARDIZATIONSECTOROFITU4%,%6)3)/.!.$3/5.$42!.3-)33)/.'%.%2!,02).#)0,%3!.$53%22%15)2%-%.43&/24(%$)')4!,42!.3-)33)/./&()'(15!,)493/5.$02/'2!--%3)454Recommendation*(Formerly“RecommendationITU-RCMTT”)FOREWORDTheITU-T(TelecommunicationStandardizationSector)isapermanentorganoftheInternationalTelecommunicationUnion(ITU).TheITU-Tisresponsibleforstudyingtechnical,operatingandtariffquestionsandissuingRecommen-dationsonthemwithaviewtostandardizingtelecommunicationsonaworldwidebasis.TheWorldTelecommunicationStandardizationConference(WTSC),whichmeetseveryfouryears,establishesthetopicsforstudybytheITU-TStudyGroupswhich,intheirturn,produceRecommendationsonthesetopics.TheapprovalofRecommendationsbytheMembersoftheITU-TiscoveredbytheprocedurelaiddowninWTSCResolutionNo.1(Helsinki,March1-12,1993).ITU-TRecommendationJ.51wasrevisedbyITU-TStudyGroup9(1993-1996)andwasapprovedundertheWTSCResolutionNo.1procedureonthe22ndofAugust1994.___________________NOTEInthisRecommendation,theexpression“Administration”isusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.ITU1995Allrightsreserved.Nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromtheITU.RecommendationJ.51(08/94)iCONTENTSRecommendationJ.51(08/94)PageAnnexA–Parameterstobeusedforthedefinitionoffuturesystems.....................................................................1A.1Samplingfrequency..........................................................................................................................1A.2Dynamicrange..................................................................................................................................2A.3Transmissiondelay...........................................................................................................................2A.4Ancillarydata....................................................................................................................................2A.5Errorcontrol.....................................................................................................................................2A.6ISDNcompatibility...........................................................................................................................2AnnexB–Recommendationsfordigitaltransmissionofhigh-qualitysoundprogrammesexistingattheendof1993...........................................................................................................................................................3iiRecommendationJ.51(08/94)SUMMARYThisRecommendationhasbeendevelopedtohelpplannersofcircuitsfordigitalsound-programmetransmission.Itreferstothecodingformandthestudiointerface,anditlistsdifferentcodecsrecommendedforuse.Additionally,theRecommendationgivessomeguidancetodesignersoffuturesystemsontheparametersofageneralnaturewhichwillneedtobespecified.RecommendationJ.51(08/94)1RecommendationJ.511)RecommendationJ.51(08/94)GENERALPRINCIPLESANDUSERREQUIREMENTSFORTHEDIGITALTRANSMISSIONOFHIGHQUALITYSOUNDPROGRAMMES(1986;revised1994)TheITU-T,considering(a)thatitisdesirabletousecommonstandardsforthetransmissionofhigh-qualitysound;(b)thatitisdesirabletouseasfewcodeconversionsaspossibleintheinternationaldigitalsoundexchangeprocedure;(c)thattofacilitatetheexchangeofsignals,itisdesirabletorenderthetransmissioninterfacesastransparentaspossibletothetransmittedmessagecontent;(d)thatthenetworkinterfacebitratesshouldtakeintoaccountthehierarchicallevelsrecommendedbyITU-T;(e)thatitmaybeefficienttoapplybit-ratereductionanderror-protectionmethodstolowertransmissioncosts;(f)thatqualityandavailabilityshouldnotberestrictedbythesignalprocessingequipmentormethodsemployedinthetransmissioncircuit;(g)thatthereisaneedtoclearlyidentifyuser’srequirementsinthedevelopmentoffuturesystemsandintheselectionofanexistingoneforaspecificapplication,recommends(1)thatasoundprogrammeoriginatingindigitalformshouldpreferablybemaintainedindigitalformfortransmission;(2)thattheinterfacebetweenthestudioandthecodecshould,wherepossible,beindigitalformandinaccordancetoITU-RRecommendationBS.647;(3)thatparameterslistedinAnnexAshouldbeusedforguidanceinthedefinitionoffuturesystems;(4)thattheselectionofatransmissionsystemshouldbemadeamongthoserecommendedbyITU-Rforhigh-qualityapplications(AnnexBlistssuchRecommendationsexistingattheendof1993).AnnexAParameterstobeusedforthedefinitionoffuturesystems(ThisannexformsanintegralpartofthisRecommendation)A.1SamplingfrequencyITU-RRecommendationBS.646specifiesasamplingfrequencyof48kHztobeusedindigitalstudios.Conversionofsamplingfrequencyleadstoareductionofsignal-to-noiseratioanderodesthesystembandwidth;italsointroducesanadditionaldelay.Forcontributionofsound-programmesignalsofdigitalstudioqualityitisrecommendedtomaintainthe48kHzsamplingfrequency._______________1)FormerlyReco