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Canon XL1 3CCD Camcorder User Manual

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TemporalCompression

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Interframe

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Canuseotherframesasreferences

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AFrametendstobesimilartotheframeprecedingit

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SoTCencodesonlythechangesinoneframetoanother

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Withtheexceptionofkeyframes

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FRAMETYPESANDCOMPRESSION 

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*Akeyframe=acompleteimagecompressedusingintraframecompression

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notbasedonanyotherframes…alwaysthefirstframe

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importantforrandompointsastheytheonlyframesthatcanbedecodedallbythemselves

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mostauthoringcodecs,likeMotionJPEGandDVuseonlykeyframes–makeseditingeasier

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*Deltaframe=compressedusinginterframecompression+containsonlyportionsoftheadjacent

framethataredifferent

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Fortypicalcontent,adeltaframemightbeonly10‐20%thesizeofthesameframeatthesame

qualityasakeyframe

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2maintypes:P‐frames(predictive–basedonpreviousframe)&B‐frames(bi‐directional–based

onpreviousandsubsequentframes)

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Note:

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Codecsvaryinhowwelltheyencodecomplexframetransitions.Forexample,fadesupanddownare

verydifficultforsomecodecs,butsomenewercodecshavecodebuiltintohandlefades.

COLOURMODES

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‐Waycodecsdescribecolour=important

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3basictypesofcolourintoday’scodecs:

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