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1、上海交通大学硕士学位论文ABSTRACTWiththewideapplicationandfastdevelopmentofnetworkand
multimediatechnology,itbecomesatrendtotransmitvideosthroughthe
network.However,thebandwidthislimited,andthevideodataneedstobe
compressed.Tomeetthisdemand,manyvideocodingstandardscameout,
includingMPEG-
2、4,MPEG-2,H.264,AVSandHEVC.Videoresourcesare
various,andterminalequipmenthavedifferentabilitiestoprocessvideo
streams,suchasdisplayabilityandstorageability.Consideringthis,video
transcodingtechniquescanbeusedtosolvetheproblems.HEVCisthelatestvideocodingstandard,whichcanimpro
3、veabout
50percentofcompressingefficiencycomparedwithH.264.AVSwas
developedbyChinaandpalyedasiginificantroleinChinesemarkets.To
makeAVSmorecompatiblewithinternationalstandards,westudiedthe
AVStoHEVChigheffiencyvideotranscodingtechniques.Andthetopic
containstwobasicideas,whic
4、haretranscoderbasedonROIdetection
usingvisualcharacteristicsandtranscoderbasedonmachinelearning.
OneofthemethodsisAVStoHEVCvideotranscoderbasedonROI
detectionusingvisualcharacteristics.Thismethodtakesaccountthe
humanvisualsystemintothetranscoder.Combinedwiththis,the
transco
5、dercanachievebettersubjectivevideoquality.Thealgorithmis
mainlycomposedoftwoparts:ROIdetectionalgorithmandfast
transcodingalgorithm.Firstly,weextractthecodinginformationcontained
inAVSvideostream.Theinformationincludespredictionmode,motion
vectorandtransformcoefficients.Wit
6、hthecodinginformation,wepartthe
videointothreekindsofregions:regionofmost-interest(mostROI),region
ofinterest(ROI),regionofless-interest(lessROI).Afterthen,thedetection
resultscanbeusedtoguidethere-encodingprocessinHEVC.For
differentregions,algorithmswithdifferentcomplexity
7、areused
accordingly.Inthisway,thecomputationalcomplexitiescanbedecreasedIII万方数据上海交通大学硕士学位论文dramatically.Experimentalresultsshowthatthealgorithmcansaveabout50%oftranscodingtime,withPSNRdroplessthan0.05dB,whilemaintainingbettervisualquality.TheothermethodisAVStoHEVCtranscodin
8、gbasedonSVM.Weapplythemachinelearningintotranscoder.Thisalgorithmdividedthetransco
