Exfo EXpert IPTV Test Tools (FTB-200v2) Manual de usuario descargar pdf (Pagina 52)

52



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.



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

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 81 82

Sin comentarios

Exfo EXpert IPTV Test Tools (FTB-200v2) Manual de usuario Pagina 52