Exfo EXpert IPTV Test Tools (FTB-200v2) Instrukcja Użytkownika Pobierz pdf (Strona 65)

65



bearerchanneltosupportreliablevideo.Thisvideoservicequalitymetricisexpressed

intherangeof0.0to50.0,asdefinedin[14].

VSTQcanbecalculatedbyamappingfunctionfromPeakSignal‐to‐NoiseRatioPSNR

valuesasfollows:



VSTQ=max(0,min(50,(PSNR‐12)*1.8))



Ofcourse,VQmon/HDusesamoresophisticatedalgorithmtocalculatetheresulting

VSTQ

score,whichtakestime‐varyingdistributionsofnetworkimpairmentsandrecency

intoaccount.



Note:TheVSTQscorethatVQmon/HD’sAPIfunctionproducesactuallyrangesfrom0

to100.Thisvalueisscaledby2togethalf‐pointaccuracyforthescore.

A.2.3.3 DegradationFactors

Tofacilitatetroubleshooting,VQmon/HDhastheabilitytoobtainabreakdownof

factorscontributingtoqualitydegradation.VQmon/HDreportstheseverityofquality

degradation(onascaleof0‐10,with0indicatingnodegradationand10indicatingthe

mostseverelevelofdegradation)attributabletoeachofthefollowingfactors:

 Packetloss

 Audio‐videosync

 Codecquantization

 GOPlength

 Codecbandwidthrestriction

 Frameresolution

 Packetdiscardsduetojitter

 Framerate

 (One‐way)delay

 Recency



*Note:Information in this document is proprietary to Telchemy, Incorporated and was

published with its permission.

1 2 ... 60 61 62 63 64 65 66 67 68 69 70 ... 81 82

Brak uwag

Exfo EXpert IPTV Test Tools (FTB-200v2) Instrukcja Użytkownika Strona 65