Slides_Chapters_1_to_22PPT英文课件Slides_Chapter20

Chapter20Videofundamentals,PracticalImageandVideoProcessingUsingMATLAB,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Whatwillwelearn?,Whatisananalogvideorasterandwhatareitsmaincomponentsandparameters?WhatarethemostpopularanalogTVandvideostandards?Whatisdigitalvideoandhowitdiffersfromanalogvideo?Whatarethemostpopulardigitalvideostandards?Howiscolorinformationencodedinanaloganddigitalvideosystems?Howcanweread,manipulate,andplaydigitalvideofilesinMATLAB?,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Videosignal:1Danalogordigitalsignalvaryingovertime,whosespatio-temporalcontentsrepresentasequenceofimages(orframes)accordingtoapredefinedscanningconvention.Mathematically,acontinuous(analog)videosignalwillbedenotedf(x,y,t),wheretisthetemporalvariable.Ananalogvideosignalreferstoa1Delectricalsignalf(t)thatisobtainedbysamplingf(x,y,t)intheverticalandtemporaldimensions.Adigitalvideosignalisalsosampledalongthehorizontalaxisofeachframe.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Scanningraster,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Scanandretrace:(a)Progressivescan(b)Interlacedscan,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,BlankingintervalThetimeintervalattheendofeachline(horizontalretrace)orfield(verticalretrace)duringwhichthevideosignalmustbeblankedbeforeanewlineorfieldisscanned.RefreshrateTherateatwhichimagesare.Typicalvalues:48Hz(cinema)60Hz(conventionalTV)75Hz(computermonitors),ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Analogmonochromevideoscanningsystemsnotation:Totalnumberoflines(includingsyncandblankingoverhead)Refreshrate(inHz)(whichwillbeequaltothefieldrateforinterlacedscanortheframerateforprogressivescan)Indicationofinterlaced(2:1)orprogressive(1:1)scanExamples:NorthAmericananalogTVsystem:525/60/2:1(525/59.94/2:1)EuropeanSDTV:wouldbe625/50/2:1.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Morecompactnotation:Concatenatingthenumberofvisiblelinesperframewiththetypeofscanning(progressiveorinterlaced)andtheverticalfrequency(roughlyequaltotheframerate).Examples:480i29.97and576i25.HDTVstandards:evenmorecompactnotation(numberoflinesandthetypeofscanning).Examples:720pand1080i.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Aspectratio(AR)=theratioofframewidthtoheight.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Gammacorrection:Theprocessofcompensatingfornon-linearitiesinimageacquisitionandimagedisplaydevices.Typicallyperformedatthetransmitterside.Bygamma-correctingthesignalbeforedisplayingit,theintensityoutputofthedisplayisroughlylinear.Byproduct(“amazingcoincidence”):alsocodestheluminanceinformationintoaperceptuallyuniformspace,thuscompensatingforthenonlinearcharacteristicsofthehumanvisualsystem.Moreover,thegamma-correctedsignalalsobecomeslesssensitivetonoise.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,GammacorrectioninTVandvideosystems,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Basicconceptsandterminology,Componentanalogvideo(CAV):colorvideorepresentationthatusesthreeindependentone-dimensionalcolorcomponentsignals(e.g.,RGBorYCBCR),freefrommutualinterference.Compositevideo:combinestheintensityandcolorinformationintoacompositesignal.BackwardcompatiblewithlegacyB&WTVsystems.Reliesonthefactthatthechrominancecomponentscanbeencodedusingasignificantlysmallerbandwidththantheluminancecomponent.Combinebrightnessandcolorintoonesignal,attheexpenseofintroducingacertaindegreeofmutualinterference.S-video(alsoknownasY/Cvideo):twocomponents,luminanceandamultiplexedchrominancecomponent.S-videosystemsrequirelessbandwidth(ordatarate)thancomponentvideo,andproducebetterimagequalitythancompositevideo.,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Monochromeanalogvideo,Analogvideoraster,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Monochromeanalogvideo,Spectralcontentofmonochromeanalogvideo,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Colorinvideo,NTSCspectrum,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Analogvideostandards,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Digitalvideobasics,Samplinginthehorizontal,vertical,andtemporaldimensions,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Analog-to-digitalconversion(ADC),ADC,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Analog-to-digitalconversion(ADC),Samplingpoints,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Analog-to-digitalconversion(ADC),Assignmentofquantizationlevelsforcompositeandcomponentvideo,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Colorrepresentationandchromasubsampling,Mostcommonchromasubsamplingpatterns,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,Digitalvideoformatsandstandards,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,TheRec.601digitalvideoformat,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc.Allrightsreserved.,TheRec.601digitalvideoformat,ByOgeMarquesCopyright2011byJohnWiley&Sons,Inc