Exfo EXpert IPTV Test Tools (FTB-200v2) Manual do Utilizador descarregar pdf (Página 70)

70



 ErrorsinPMT,PAT,PID/PSI(PacketIdentifier/ProgramSpecificInformation)Errors

willcausethesettopboxlosecontactwiththestream.Theseerrorsmayoriginateat

anyoftheMPEGtransportmultiplexerswhennewstreamsareinserted.



A.4 PCRJitter



PCR(programcounterreference)timestampsisgeneratedbytheMPEG‐2encoder

andreceivedthroughoutthesubsequentlinksinthenetworkatleast100millisecondsapart.

ThedecoderusesthePCRtolockitsown27MHzclocktotheencodersystemtimeclock(STC).

This27Mhzclockisverysensitivetovaria

tionscausedprimarilybypackettransmissions

delays.Therefore,measurementofthePCRtimestamparrivaltimevariationcalledcommonly

“PCRjitter”isessential.The27Mhzoscillatoritselfmaynotexceed500nsecofinternaljitter

perTR101290.



1 2 ... 65 66 67 68 69 70 71 72 73 74 75 ... 81 82

Sem comentários

Exfo EXpert IPTV Test Tools (FTB-200v2) Manual do Utilizador Página 70