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领先的数字音频压缩技术
Introduction
Withtherapiddevelopmentofdigitaltechnology,digitalaudiocontenthasbecomeanintegralpartofourlives.However,digitalaudiofilesareverylargeinsize,whichlimitstheirusageandtransferability.Therefore,audiocompressiontechnologyhasemergedasoneofthemostimportanttechnologiesinthefieldofdigitalaudio.Themaingoalofaudiocompressiontechnologyistoreducethesizeofdigitalaudiofileswhilepreservingtheirquality.Therearevariousaudiocompressiontechniquesavailable,butthemostcommonlyusedandleadingtechnologyistheMPEGaudiocompressiontechnology.
MPEGAudioCompressionTechnology
MPEG(MovingPictureExpertsGroup)isastandardizationgroupthatwasformedbytheInternationalOrganizationforStandardization(ISO)andInternationalElectrotechnicalCommission(IEC)inordertodevelopstandardsforthecompressionandtransmissionofdigitalaudioandvideocontent.
MPEGaudiocompressiontechnologyisbasedonapsychoacousticmodel,whichisamodelthatsimulatesthehumanauditorysystem.Thehumanearissensitivetodifferenttypesofsounds,andthepsychoacousticmodeltakesthesesensitivitiesintoaccountwhencompressingdigitalaudiofiles.Themodelidentifiesthepartsoftheaudiostreamthatarenotperceptibletothehumanearandremovesthem,therebyreducingthesizeofthefilewithoutaffectingitsperceivedquality.
TherearevariousversionsofMPEGaudiocompressiontechnology,includingMPEG-1,MPEG-2,andMPEG-4.MPEG-1isthefirstversionthatwasdevelopedandiscommonlyusedfordigitalaudiotransmissionandstorage.ItusesacompressionalgorithmcalledMP3(MPEG-1AudioLayer3)tocompressaudiofiles.MP3isalossycompressiontechnique,whichmeansthatsomeoftheoriginalaudiodataisdiscardedduringcompression.However,thediscardeddataischosenbasedonthepsychoacousticmodelandisthereforenotperceptibletothehumanear.MP3isthemostwidelyusedaudiocompressiontechnologyintheworldandcancompressaudiofilesupto12timestheiroriginalsize.
MPEG-2isanextensionofMPEG-1andismainlyusedforbroadcastinganddigitaltelevision.ItsupportshigherbitratesandsamplingratesthanMPEG-1andcancompressaudiofilesupto24timestheiroriginalsize.
MPEG-4