Canon XL1 3CCD Camcorder User Manual

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1.Interlacedversusprogressivescan

‐NTSCvideohasaframerateof29.97framespersecond(fps),orroughly30fps,withtwofieldsper

frame(59.94fieldspersecond).PALvideois25fps(50fieldspersecond).

‐Interlacedvideodoesnotlookgoodonprogressivescanmonitors.Compressiontechniquesforthe

webusuallychangethevideofrominterlacedscantoprogressivescan.Themostbasicmethodforthis

changeistodiscardonefieldandduplicatetheothertocreatethefullframe.

‐Thisprocessreducestheamountofdatayoustartedwithby50%,whichcanadverselyaffectthe

finalquality.Themorecomplexmethodisfortheencodertoreadbothfieldsandinterpolate(blend)

themintoasingleframebychangingthepixelstosmoothoutthetimingdifferencebetweenthe

fields.Thismorecomplexmethodallowsyoutostillusealltheoriginaldatafromthevideoand

producehigher‐qualityoutputforprogressivescanmonitors.



2.Cameramotion

‐Cameramotionchangeseverypixelofeveryframe.Lackofcameramotion

isthesimplest,ofcourse.

‐Butmoderncodecscanencodecameramotion,suchasthatcreatedusingdollies,quitewell.Tilts

andpansaremoredifficult.

‐Dependingonthecodec,rotatingthecamera(aDutch)canbetrivialorextremelycostlyin

compressionefficiency.

‐Themostdifficultmotionforanycodecishand‐heldcameramotionwithrandomjostling.

‐Forcompression,it’smucheasiertohandlechangesofviewbyeditingratherthancameramotion,

especiallyatlowerdatarates.

‐Inpost‐production,themotionstabilizationtoolsinAfterEffectscanremoveunwantedcamera

motionbeforecompressiontoreducethesizeoftheoutputvideofile.



3.Shutterspeed

‐Slowershutterspeedsletthroughmorelight,andhencelessgrain,whichhelpscompression.

‐Slowershutterspeedsalsocausemovingpartsoftheimagetobecomeblurry,whichmakesthem

easiertocompress.



4.Backgrounds

‐Adifficultmotionforcodecsisfoliagerustlinginthebreeze



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Canon XL1 3CCD Camcorder User Manual