Topic-3：StillImageCodingStandardSeveraltypicalimage/videocompressioncodingstandardH.261、H.263:TVConferenceandVisualTelephoneSystem；JPEG、JPEG2000:StillImageCompression；MPEG-1:VCD；MPEG-2:DTV、DVD、HDTV；MPEG-4:MultimediaCommunication。JPEGstandardJPEG(JointPhotographicExpertsGroup)Reducingthesizeofphotographicimagesorcontinuous-toneartwork–picturesJPEGcompressioncanbeperformedon24-bitcoloror8-bitgrayscaleimages.JPEGCompressionArithmeticDCT:lossycompressionPredictivecoding:losslesscompressionJPEGimagereconstructionmode：Sequentialdecoding(line-by-line)；Progressivedecoding(refinementofthewholeimage)FourdifferentmodesLossySequentialDCTbasedmodeBaselineprocessthatmustbesupportedbyeveryJPEGimplementation.ExpandedLossyDCTbasedmodeenhancementstobaselineprocessLosslessmodelowcompressionratioallowsperfectreconstructionoforiginalimageHierarchicalmodeaccomodateimagesofdifferentresolutionsJPEGcodingsystemThebaselineprocessTheextendedprocessDiagramofDCTencodeanddecodeOriginalimagedataRebuildimagedataDCTIDCTQuantizerRe-quantizeQuantizetableEntropyencodeEntropydecodeCodeoutputchannel8×8subMB8×8subMBf(x,y)f’(x,y)F(u,v)F’(u,v)S(u,v)Q(u,v)Q(u,v)JPEGstandardgivethebrightnessDCTcoefficientquantizationstepJPEGstandardgivethechromaDCTcoefficientquantizationstepOriginalimagesubMBbrightnessvalueRelativeDCTcoef