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1、SOMESOFTWAREISSUESOFAREAL-TIMEMULTIMEDIANETWORKINGSYSTEMGabriel-MiroMuntean,LiamMurphyPerformanceEngineeringLaboratory,SchoolofElectronicEngineering,DublinCityUniversity,Dublin9,Irelandmunteang@eeng.dcu.ie,murphyl@eeng.dcu.ieAbstractThetransmissionofrelatedmultimediadatacausesprob
2、lemsbecauseoftheirverylargesizeandcontinuousnature.Unlikethemajorityoftheexistingsolutionsfortransmittingcontinuousmedia,whichuseconnectionlessprotocols,weproposeonethatusesaconnection-orientedprotocol(TCP/IP).Anobject-orientedapproachisusedtobuildbothserverandclient,allowingeasie
3、rsystemdebuggingandexpansion.Weimplementedabufferingmechanismwhichallowsustocontinueplayingforaperiodwhenthenetworkloadincreases.Multithreadingisusedtosolvesomeproblemswhichrequireconcurrentsolutions.1.IntroductionTheprocessoftransmissionofrelatedaudio,video,images,textand/ordataa
4、mongnetworkedcomputersisknownasmultimedianetworking.Bothaudioandvideostreamshavetimingrequirementsaswellasaneedtoplayouttheminacontinuousmanneratthereceiver.Besidestheseindividualtimingrequirements,acombinedmultimediastreamrequiressynchronizationatthereceivertobeunderstandable.Ano
5、therproblemwithmultimediastreamsistheirlargefilesize.Alotofworkhasalreadybeendone[1]toreducethesizeofmultimediafilesbyusingdifferentcompressionalgorithms,therebyreducingthenecessarybandwidthfortransmissionandthusthenetworkload.Forthesystemwehavebuilt,wehavechosenMPEGformatforcompr
6、essingaudioandvideobecauseofitshighcompressionfactoranditsabilitytoadjustthesizeofthecompressedstreamdependingontherequestedquality.Therequestedandexpectedqualityoftransmissiondependsonwherethemultimediastreamisused.Insomeapplicationsahighqualityofservice(QoS)isimportant.Inotherca
7、sestheexpectationsforQoSarelower,butasmoothflowofthemultimediastreamisdesirable.Thereweresomeproposalstoimprovemultimediatransmissionqualityliketrafficcontrolanddynamicbandwidthrenegotiationattheserver[2],dynamicbandwidthallocationandflow/congestioncontrol[3],rateshaping[4]orafeed
8、backmechanisms[5],[6].Themajority
