Exfo EXpert IPTV Test Tools (FTB-200v2) Uživatelský manuál stáhnout pdf (Strana 59)

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A.2.1.4 FrameTypeDetection

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VQmon/HDidentifiesindividualI,P,andBframesintheGoPandmeasuresthepacket

lossrateandlossdistributionoccurringineachframetyp e.Forunencryptedvideostreams,

VQmon/HDperformspictureheaderdecodingtoidentifyindividualframes,GoPsize,and

framerate.Forencrypted/scrambledstreams,heuristicalgorithmsareappliedinorderto

detectframeboundarie

sandmeasureframesize. 

AsmentionedinSection2.1.1.1,theGoPstructurehasimpactonboththeefficiencyofvideo

encodingandtherobustnessofencodedvideo.VQmon/HDtakesthedifferentI,P,andB

framepacketloss/discardratesintoaccountwhencalculatingperceptualvideoquality

metrics.

A.2.1.5 Per‐frameQualityAnalysi s

VQmon/HDperformsper‐framequalitycalculationusingtheframetype,framesize,

codectype,videobandwidth,andpacketlossdata.Theproportionofeachframetype

impairedbyloss/discardisreported,alongwiththeproportionofBandPframesimpaired

duetothepropagationoferrorsfromearlierreference(IorP)framesintheGoP

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A.2.1.6 PerceptualQualityModel

VQmon/HD’sperce ptualqualitymodelcalculatesestimatedperceptualquality(MOS)

scoresusingtheper‐framequalitymetricsandcontentanalysisasinputs.Thecalculation

modelconsidersthesensitivityofthecontenttoqualitydegradation(e.g.,thatframefreezes

occurringduringahigh‐motionscenewillbemorevisibleandannoyingthanthoseoccurring

duringastaticscene)andoth

ersubjectivefactorssuchasviewerreactiontime,recency,and

temporalmasking(seeSection2.1.3.2).

A.2.1.7 VQmonMarkovModel(VMM)

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VQmon/HDusesafour‐stateMarkovModeltogatherandreportpacketlossstatistics

for“burst”periods(wherequalityissignificantlydegraded)and“gap”periods(periods

betweeneachburstintervalwhenqualityisrelativelyunimpaired).

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Exfo EXpert IPTV Test Tools (FTB-200v2) Uživatelský manuál Strana 59