Lesson 28 Digital Storage Media电子技术专业英语教程

Unit10DigitalMultimediaSystemsLesson28DigitalStorageMedia《电子技术专业英语教程》冯新宇主编电子工业出版社《电子技术专业英语教程》228DigitalStorageMedia•Backgrounds•Texttour•Languageinuse–Vocabulary–Structure–Reading/writingtechniques2020/2/29《电子技术专业英语教程》3•Terminology–fiber-optic【计】光导纤维–servon.伺服，伺服系统；【计】伺服装置–Hypermedia【计】多介质的，超媒体–CD-DA数字音频光盘–compact-disc激光唱片，压缩磁盘，光盘–CD-ROM只读存储器，只读光盘–FiberDistributedDataInterface光纤分布式数据接口–seektime寻道时间–ordersofmagnitude数量级Backgrounds2020/2/29《电子技术专业英语教程》4Texttour•Outline-Whatisdigitalstoragemedia?-Storage•CDROM•CDROMdevelopment-Network•Whyshouldtheintroductionofnetworkstorage?•Therealizationofnetworkedstorage2020/2/29《电子技术专业英语教程》5Whatisdigitalstoragemedia?•digitalstoragemediareferstobothstorageandcommunicationcapabilities•Thesehaveincreasedincapacitymorethanathousandfoldinthepastdecade,allowingdigitalmultimediatoemergeasacosteffectivecompetitorforanalogapproaches.•In1985,CD-ROM(compactdiscread-onlymemory)withacapacityofmorethan600Mbytesbutamanufacturedcostunderadollarwasfirstappliedtoelectronicpublishing.Similarly,fiber-opticcablenowmakesgigabit-per-secondcommunicationchannelsarealityworldwide.2020/2/29《电子技术专业英语教程》6CD-ROM•CD-ROMs,themostcosteffectivestoragemediumfordistributinglargequantitiesofdigitaldata,arerelatedtoregularcompactdiscs-thatis,CD-DA,orcompact-discdigitalaudio.•Bothsupportdirectaccesstoindividualsectorsofdatathatcanstore1/75secondofCD-qualitydigitalaudioinCD-DAformat,using2,336bytes,or2,048bytesofarbitrarydigitaldatainCD-ROMformatwiththerestofthespaceforerrorcorrection.Thus,CD-ROMdatatransferspeedis150Kbytespersecondor1.2Mbitspersecond.2020/2/29《电子技术专业英语教程》7CDROMdevelopment•Anelaboratesystemofoptics,servos,andsignaldecodingcircuitsallowsdatatobeaccessedwithinasecond.ISO9660(basedontheHighSierrastandard)specifiesthevolumeandfilecharacteristics,allowingaccessthroughnearlyanyCD-ROMdriveandoperatingsystem.EffortsoftheRockRidgeGrouphaveextendedtheutilityofISO9660forUNIXsystemsandservers.2020/2/29《电子技术专业英语教程》8CDROMdevelopment•Compactdiscsarepartofthefamilyofopticalmedia.Thereareprospectsforfurtherimprovement,includingwrite-onceanderasablediscsofvaryingsizes.Forexample,announcementsindicatethatin1992,write-onceCD-ROMdriveswillcostunder$3000,andminidisk(2.5-inch,128-Mbyte)driveswillcostaboutthesameasthoseforCD-ROMs,handlingbothformats.•Magneticdisksarereadilyavailablewithcapacitiesontheorderofagigabyte,buttheyarenotlow-cost，removable,orproducedbymassreplication.Useofcaching,memoryhierarchies,andminimalperfecthashingwillmakeallstorageunitsevenmoreeffectivecontributorstodigitalmultimedia.2020/2/29《电子技术专业英语教程》9NetworkWhyshouldtheintroductionofnetworkstorage?–Whilefiber-opticconnectionsarethemostcost-effectiveschemeforrapidlytransmittinglargevolumesofdigitaldata，agreatdealofresearchregardingnetworkedmultimediaisrequired.–TheFiberDistributedDataInterfaceoperatesat100Mbps,andconnectioncostsdroppedbelow$5000intheearly1990s.Gigabit-per-secondnetworksarebeingtested,andwillformthebackbonefornationaltelecommunication.However,researchregardingnetworkprotocols,localareanetworkandworkstationarchitectures,andoperating-systemsupportsoftwarefordigitalmultimediaisstillinitsinfancy.Thefirstinternationalworkshopexclusivelyonthesetopicswasheldlatein1990.2020/2/29《电子技术专业英语教程》10Therealizationofnetworkedstorage•AsynchronoustransfermodenetworkssupportbothvariableandconstantbitrateservicesatveryhighspeedsandserveasthebasisfortheBroadbandIntegratedServicesDigitalNetwork.–Streamsofdigitalmultimedia,includinguncompressedlivevideo,canusetheconstantbitrateservices.–Thesetypesoffastpacketswitchingcansupportreal-timecommunicationwithreducedjitter(Jitteriscausedbydelaysofpackets).–Yetmanyquestionsremainregardingsynchronizationofrelateddatatypes,dynamicadaptationtodifferentterminalandnetworkservices,andreal-timerequirementsforhypermedia.–Researchisalsoneededonratestructures,spectrumandchannelallocation,andhandlingofscalablerepresentationsofvideostreams.2020/2/29《电子技术专业英语教程》11•Networkandoperating-systemconcernscoalescebecauseoftheneedforopensystems,synchronization,andfasttransferfromnetworktopresentationunit.–Highperformanceandreliabilityarealsoimportant.Researchisproceedingonobject-orientedmodelstohandlethevariousclassesofmultimedia,abstractionsforcontinuousmedia(forexample,anaudiostream)I/O,andconnectionarchitecturesfornetworksandworkstation.–Thereisatrade-offbetweennetworkreliability,howcloselythenetworkapproximatesprovidingaconstantratestream,andotherfactors.–Withoutbuffering,thestreamofdatamustbecarefullyprepared,suchasbyinterleavingdataonstorageunits.–ThatisespeciallyimportantwithCDROM,whereseektimesareonetotwoordersofmagnitudeslowerthanwithmagneticdisks.Asmemorypricesdecline,however,bufferingofmultimediadatawillallowfastprocessorstocompensateformanyperformanceproblemsindigitalstoragemedia.2020/2/29《电子技术专业英语教程》12•Vocabulary–backbonecoalesce•Reading/writingtechniquesLanguageinuse2020/2/29《电子技术专业英语教程》13Vocabulary2020/2/29《电子技术专业英语教程》14backboneindictionary–Thebackboneorspine.脊骨或脊柱–Thebackboneofathesis.论文的主旨–Havi