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1、VideoCompressionforthePandoraMultimediaSystemDJClarkeOlivettiResearchLimitedORLTechnicalReport94-6Contents1Introduction11.1ThePandoraSystem:::::::::::::::::::::::::::11.2RequirementsontheVideoCompressionsystem:::::::::::22ChoiceofVideoCompressionalgorithm32.1StandardTechniques::::::::::::::
2、:::::::::::::32.2Horsepower::::::::::::::::::::::::::::::::32.3Thechosencompressionalgorithm:::::::::::::::::::42.4Decompression::::::::::::::::::::::::::::::62.5TestImages::::::::::::::::::::::::::::::::83HardwareOverview123.1IntegrationwiththerestofthePandoraBox:::::::::::::123.2FlexibleH
3、ardware::::::::::::::::::::::::::::153.3CompressionRatio::::::::::::::::::::::::::::174Conclusion181Introduction1.1ThePandoraSystemIn1990OlivettiResearchLimitedinCambridgebegantodeployanetworkofMul-timediaworkstationsknownasPandora.EachWorkstationconsistedofacomputerrunningUnix(anARM-basedm
4、achinefromAcornComputer)andanadd-onbox(the`PandoraBox')tohandleVideoandAudiotrac.[3][2]TheVideoandAudiowascarriedonthelocal50Mbit/snetwork,theCambridgeFastRing(CFR).[1]Thisset-upallowedmultiplestreamsofvideoandaudiotobesentconcurrentlybetweentheworkstationsand,later,aleservermachineaswell
5、.ThewholewasintegratedsothatausercouldmanipulatetheVideoandAudiousingfamiliar-1lookingX-Windowstools,withtheVideoappearinginoneormorewindowsontheWorkstationscreen.(SeeFig15.)ThePandoraBoxisaMIMD(MultipleInstructionMultipleData)multiprocessorimplementedusingInmosTransputers.[4]Thearchitectur
6、eoftheBoxisoutlinedbelowinFig1.Figure1:ArchitectureofaPandoraBoxVideoistransferredbetweentheCapture,ServerandMixersubsystemsbymeansofFIFO(FirstInFirstOut)buers.TheCompressionhardwareislocatedinthesebuereddatapaths,asshowninthegure.1.2RequirementsontheVideoCompressionsystemPandorawasdesig
7、nedtohandleonlymonochromevideo.Colourvideowouldhaveincreasedthedatarateandmadethesystemmorecomplex;itwasfeltatthattime,(1989)thatwedidnotneedcolourvideotodoresearchintolivenetworkedcontinuousmedia.Thechosennetwork,theCFR,hadmanygoodpropertiesforliveconti