Exfo EXpert IPTV Test Tools (FTB-200v2) Manuel d'utilisateur télécharger pdf (Page 64)

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 RelativeMOS‐Visanestimatedperceptualqualityscorethatconsidersthe

effectsofcodec/quantizationlevel,theimpactofIPTVimpairments(e.g.,packetloss)

ontheGoPstructureandvideocontent,andtheeffectivenessoflossconcealment

methods—butdoesnotconsidertheimagesize/resolution,framerate,orscanning

method(interlacedvs.progressive).

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 AbsoluteMOS‐Visanestimatedperceptualqualityscorethatconsidersallthe

abovementionedfactorsaswellasimageresolution,framerate,andtheuseof

progressivevs.interlacedscanning.

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Somevideoformatsofferinherentlyhigherperceptualqualitythanothers—for

example,inunimpairedconditions,thequalityofanHDbroadcastwillbehigherthan

thatofSD;1080pbetterthan1080ior720p;60framespersecondbetterthan30fps,

etc.VQmon/HD’sAbsoluteMOS‐Vscoretakesthesefactorsintoconsideration,and

thusprovidesanaccurateestimateof“overall”perceptualquality.

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Becauseitisindependentofimageresolution/framerate,theRelativeMOS‐Vscore

helpsprovideanindicationofvideoqualityrelativetotheidealforagivenvideo

format.

Example:AnIPTVserviceprovideroffers480iSD,720pHD,and1080pHDbroadcasts.

Assumingunimpairedconditions,theservicesmightreceivethefollowingscores

(valuesprovidedforexampleonly):

AbsoluteMOS‐V:480i=4.0720p=4.31080p=4.7

RelativeMOS‐V:480i=4.5720p=4.51080p=4.5

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RelativeMOS‐Vcanbeusedtosimplifyalertthresholdingincaseswheremultiple

videoformatsareinuse.

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A.2.3.2 VQmon/HDVideoServiceTransmissionQualityMetric‐VSTQ

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VQmon/HDproducesavideoservicesqualitymetric,VSTQ(VideoService

TransmissionQuality),whichisacodec‐independentmeasureoftheabilityofthe

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Exfo EXpert IPTV Test Tools (FTB-200v2) Manuel d'utilisateur Page 64