The analogical flows (video and audio) digitalizzatis come, that is you/they are converted in a sequence of 0 and 1 through a converter A/D and compressed with the algorithm MPEG2. If necessary criptatis come. These flows (anymore some information for the decoding and for the synchronism) multiplexatis together come in a stream DVB/MPEG2 to form the PES (Packetized elementary stream). Every PES is distributed in packets of transport TPS long 188 byte, containers a byte of synchronism, 3 byte of prefix (PID), of which currently only the 2 byte less meaningful you/they are used, and 184 byte said profits payload.
1 SYNC3 PID184 PAYLOAD
Every packet therefore, according to the standard DVB/MPEG-2 it is identifiable through his/her PID. The value of the PID of every packet of the PES is decided by the drawer. Nevertheless there are some packets with PID consosciuto that has some particular meanings. Everything this is established in the document DVB-him (Service information).
XXH00 00HPAT (Program Association Table)
It furnishes Us the relationship among the CHs ID (Identificativo of the channel) of all the channels and the Pid PMT associated to every channel.
XXHYY YYHPMT (Program Association Table)
Containing Chart all the values of the PIDs (audio, video, dates, clock, ecm/emm, etc) necessary for the vision of a channel.
The providers send in uplink to the satellite these packets modulated in QPSK. Multiplexatis together often come more channels to the purpose of utlizzare the whole gang.
The satellite trasla toward the frequencies of downlink the harmonic signal modulated in phase, changes, if necessary, its polarization and it rebroadcasts him/it I pour earth.
To earth a receiving system satellitare will deal him with to make to visualize on a common television a datum channel.
OPERATIONS OF AN IRD
 LNB: Low Noise Block. You/he/she is placed on the fire of the parabolic spar. Its assignment is that to amplify the signal and traslare the gang of the frequencies received by the satellite, currently inclusive among 10.700 and 12.750Mhz, in a gang of lower frequencies denominated 1° IF (first intermediary frequency) inclusive among 950 and 2150



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