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Canon XL1 3CCD Camcorder User Manual

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timetonoticeeachartifact;thus,theimagequalityperframemustbehighertoprovidethesame

perceivedquality.

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Consequently,youshouldtrytousethesourceframerateifpossible,andnolessthanhalfthe

sourceframerate,unlessyoutargetreal‐timestreamingtodial‐upmodemusers.

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Raisingframeratesgenerallypaysoffmorethanraisingframesizesinimprovingtheuser

experience.



NEGOTIATINGFRAMEDROPPING

‐Somecodecsoptionallyorautomaticallyreduceframerateinordertomaintainthequalityof

difficultframesandkeepwithinthetargetaveragedatarate.Thisprocessgenerallytakestheformof

acontrolthatsetstheminimumimagequalityperframe.Ifthebitsthatthecodecwouldnormally

allocatetoagivenframearen’tsufficienttohitthetargetquality,itraisesthedataratefortheframe

totheminimumrequiredforquality;thendropsoneormoreframesthatfollowtokeeptheaverage

datarateontarget.

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Whetherthisprocessisappropriatedependsonthecontent.

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Variousfactorscomeintoplayhere:

‐Keyframerate

‐Samplerate

‐Channels



Deliverymethodsforvideo





Themethodyouusetocompresscontentdependsgreatlyonhowyouplantodeliverit.

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Disc‐baseddelivery

‐Discplaybackkeepsgettingbetterevenasthefocusoftheindustrymovestonetworkdelivery.

‐Disc‐baseddeliveryworkswell,andtheavailabledataratesareradicallyhigherthanthoseforweb

video.



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Downloadablefiles

‐Themostbasictypeofvideoonthewebisasimple,downloadablefile.

‐Theadvantageofdownloadablefilesisthatusersdon’texpectreal‐timeplaybackduringthe

download.

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