Axis P1254 - Page 17

AXISP1254NetworkCamera
Video
•Overlaysettings.SeeAboutoverlaytextonpage20.
ClickSavetoapplythenewsettings.
H.264
H.264,alsoknownasMPEG-4Part10/AVC,isavideocompressionstandardthatprovideshighqualityvideostreamsatlowbitrates.
AnH.264videostreamconsistsofdifferenttypesofframessuchasI-framesandP-frames.AnI-frameisacompleteimagewhereas
P-framesonlycontainthedifferencesfrompreviousframes.
TheH.264streamsettingscanbeconguredfromtheVideo>VideoStreampage.SelecttheH.264tab.Thesettingsdenedinthis
pagewillapplytoallH.264streamsthatdonotuseastreamprole.
TheGOPlengthisthenumberofframesbetweentwoconsecutiveI-frames.IncreasingtheGOPlengthmaysaveconsiderablyon
bandwidthrequirementsinsomecases,butmayalsohaveanadverseaffectonimagequality.
TheAxisproductsupportsthefollowingH.264prole(s):
•Baseline.TheBaselineproleisrecommendedforclientsthatdon’tsupportCABACentropycoding.
•Main.TheMainproleprovideshighercompressionwithmaintainedvideoqualitycomparedtotheBaselineprolebut
requiresmoreprocessingpowertodecode.
•High.TheHighproleprovidesreducedbitrateandhighercompressionwithmaintainedvideoqualitycomparedtothe
Mainprolebutrequiresmoreprocessingpowertodecode.
ThebitratecanbesetasVariablebitrate(VBR)orMaximumbitrate(MBR).VBRadjuststhebitrateaccordingtotheimage
complexity,usingupmorebandwidthforincreasedactivityintheimage,andlessforlowerimageactivity.Whentheactivityin
thesceneincreases,thebitratewouldusuallyincreaseaswell.Ifthereisasurplusinbandwidth,thismaynotbeanissueand
selectingVariablebitrate(VBR)willbesufcient.Butifbandwidthislimited,itisrecommendedtocontrolthebitratebyselecting
Maximumbitrate(MBR).Whentheactivityinthesceneincreases,VBRadjuststhebitrateaccordingtothecomplexity,usingup
morebandwidthforincreasedactivityinthescene,andlessforlowersceneactivity.MBRallowsyoutosetatargetbitratethat
limitsthebandwidthconsumption.
TheMBRtargetbitrateworksliketheceilingofatent.Itlimitsthebitrate,whilemaintainingsomeexibility.Thebitrate
maybounceupanddownwithinthesettargetbutwhenitnearsthesettargetvalue,thelimitationkicksin.However,because
MBRwillalwaysprioritizeacontinuousvideostream,itallowstemporaryovershootsfromthetargetbitrate.Becausesettinga
targetvaluepreventsthebitratefromincreasing,framerateandimagequalityareaffectednegatively.Topartlycompensatefor
this,selectwhichvariableshallbeprioritized,framerateorimagequality.Notsettingaprioritymeansthatframerateand
imagequalityareequallyaffected.
Thecurrentbitratecanbesettoappearastextoverlay.UnderOverlaySettings,selectIncludetextandenterthemodier
#bintheeld.
Toapplythesettings,clickSave.
Axis’ZipstreamTechnology
Zipstreamisabitrate-reductiontechnologyoptimizedforvideosurveillance.ZipstreamreducestheaveragebitrateintheH.264
streambyremovingunnecessarydataandmakesitpossibletoallowhigherresolutions,reducestoragecostortokeeprecordingsfor
alongertime.Toreducethebitrate,Zipstreamreducesthenumberofbitsintheareasoftheimagethatarelessinterestingfroma
videosurveillanceperspective,forexamplethebackground.Imagedetailsthatareimportantforforensicvideoanalysis,forexample
facesandlicenseplates,arepreservedwithenoughnumberofbits.
TheseZipstreamstrengthoptionsareavailable:
•Off.Zipstreamdisabled.
•LowestZipstreamstrength.Lowbandwidthreduction.Novisiblequalitydegradationinmostscenes
•MediumZipstreamstrength.Mediumbandwidthreduction.Limitedvisualqualitydegradationinnotprioritizedareasin
somescenes
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