Exfo EXpert IPTV Test Tools (FTB-200v2) Bedienungsanleitung PDF herunterladen (Seite 52)

52

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Interleaving‐inwhichthevideostreamissplitintoalternateframesandeachencoded

separately

Macro‐blockerrorconcealment‐spatia llycorrespondingmacro‐blocksarecopiedfromthe

previousframe

Theseapproachescanhelpconsiderablywithtolerancetopacketloss.

A.1.1.3 PlayoutBufferConfiguration

Itisassumedthatbothvideoconferencingandstr

eamingvideosystemsprovidea

playoutbuffer;however,theconfigurationoftheseisquitedifferent.Itishighlydesirableto

determinewhetheranapplicationisstreamingorinteractive,sincetheplayoutbuffer

configurationistypicallyverydifferentforthesetwoapplications.

Followingareexamplesfortheplayoutbuffersettings:

Videoconfer

encing‐nominal100ms(0.1seconds),adaptive

StreamingVideo‐nominal3,000ms(3seconds),fixed

A.1.2  Encoding/DecodingImpairments

Whiletransmissionimpairmentssuchaspacketlossareacommonsourceofvideo

qualitydegradation,qualitycanalsobeaffectedbytheencoding/decodingprocessitself;i.e.,

somedistortioncanbeintroducedbythebitrateandcodecused.

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A.1.2.1 ImpactofCodingBitrateonVideoQuality

ForatypicalMPEG‐2encodedvideostreamwithstandardresolution720x486,GOP

sequenceIBBPBBPBBPBBPBB,at30framespersecond,themeansquareerror(MSE)dueto

bitratecanbeapproximatedby:

MSE

=0.00001+1.5/(B+B



/30000).

WhereBisthebitrateinkilobitspersecond.Thecorrespondingpeaksignal‐to‐noiseratio

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Exfo EXpert IPTV Test Tools (FTB-200v2) Bedienungsanleitung Seite 52