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1、上海交通大学硕士学位论文ABSTRACTThemainobjectofvideocodingistominimizethedistortionsubjecttoaconstraintbitrate.Rate-distortionanalysisandratecontrolplayakeyroleinvideocodingandcommunicationsystemsbyprovidingtherate-distortionoptimizedcompressionperformance,assuringthesuccessfulnetwork
2、transmissionofthecodedvideodata,andachievingthebestvisualqualityatthereceiver.Amongvariousmacroblocktypes,H.264/AVCobtainsthebestcompressionperformancebytherate-distortionoptimization(RDO)algorithm.However,duetothecharacteristicofRDOalgorithmandtheuseofsomerefinedmotionest
3、imationmethods,thecomputationcomplexityincreaseslinearlywiththenumberofmacroblock(MB)type,andthevideoprocessingtimeincreasesgreatlyInaddition,MBactivitycharacteristicisdistinctlydifferentamongtheMBsinthesameframe.ThesamequantizationparameterisusedforalltheMBs,apparentlyiti
4、snotperfect.Inthisthesis,fromtheextensiveexperimentresultsofvariousQCIFvideotestsequence,itisclearthatthestrongcorrelationofMBtypeexistsinspatialdomain,nomatterintraIframeorinterP/Bframe.InordertoanalyzetheMBtyperelationshipbetweentheneighborMBs,meanofsquareddifferenceands
5、umofabsolutedifference(SAD)areintroducedtomeasurethecomplexityofMBinIframeortheactivityofMBinPBframe,respectively.Thenthestrictpredictionruleissetdown.Finally,anadaptiveMBencodingalgorithmisproposedbasedonMBtypespatialdomainprediction.AndthealgorithmisimplementedonH.264/AV
6、CtestmodelJM8.6.Extensiveexperimentalresultsshownotonlyvideocodingtimedecreasesgreatly,butalsovideoqualityandcompressionperformanceretainnoworse.Accordingly,thedisadvantageofRDOalgorithmislessenedsothattheencoderworkefficiencyisimprovedeffectively.Inaddition,duetothedistin
7、ctdifferenceamongtheMBsinthesameframe,inordertoimprovebitallocation,oneMBlayeradaptive-quantizationstrategyis-iii-上海交通大学硕士学位论文proposedbasedonJM8.6ratecontrolalgorithm.Theexperimentalresultsshowthemodifiedalgorithmimprovesthevideoqualityandensurestheoutputbitstreammoreclose
8、totargetbitrate.KEYWORDS:Rate-DistortionOptimization;MacroblockType;RateControl;PredictCo
