73
ThejoinmessageasksthenetworktosendtherequestedprogramorchanneltotheSTBby
joiningamulticastgroupcarryingthedesiredbroadcastchannel.
IGMPlatency,then,isthetimebetweenwhenthejoinmessageissentandthefirstvideo
packetisreceivedbytheSTB.
Thisparame
termeasuresnetworkperformance,butnottheenduser'sexperiencewith
regardtochannelchangingtime.
TheIGMPlatencyplusthetimeittakestofillthedecodebufferandtodecodeanddisplaythe
contentisthetotaluserexperiencetime.However,thebufferfilltimeandthedecodetime
arefuncti
onsofthenetworkarchitectureandarenotvariables.ThistotaltimeiscalledZap
Time.
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