Promax PROLINK-4 Manual De Instrucciones página 171

USER'S MANUAL. PROLINK-4
The information that appears in the Network, Service, Bouquet and Provider fields is
responsibility of the Operator in charge of the tuned transponder. The PROLINK-4 only
decodes this information, if it is present, and shows it on the screen.
4.9.3 Decoding MPEG-2 / DVB Channels, access to Digital Services.
The MPEG-2 is an ISO/IEC (13818-1) standard that defines the audio and video
multiplexation in chains of bits form, grouped in fixed length packets. These standards
offer two multiplexation layers: the first one (Packetized Elementary Stream) manages
the synchronization between video and audio, whereas the second one depends on
used transmission media. For error-free medias, this layer is the Program Stream,
whereas at not error-free medias is called Transport Stream.
In digital television is used the Transport Stream, in which two types of packets
can be distinguished clearly: those that content packetized video or audio, and those
that content the information necessary to be able to accede to video or audio. These
last ones form the specific information of the programs (PSI, Program Specific
Information), and allow to construct a series of tables that store the organization of the
programs or services that there are in the Multiplex, as well as data about their
conditional accesses (in case they are encrypted).
The DVB standard adds to tables MPEG-2 a few tables more than they offer
very useful complementary information in the case of digital television, between which
they emphasize the service table (Service Description Table), the network table
(Network Information Table), and the bouquet table (Bouquet Association Table).
In the list of services they will appear all the present services in the service table
according to the ETS 300 468 standard. Therefore will appear the decodable services
by any digital television decoding system that satisfies the MPEG-2 / DVB standard, as
well as the data services, the utility reserved services by the operator, and even the
discontinuous transmission services that, however, have been specified in the service
table outside of its hours of transmission.
The specification for the Service Information in DVB systems, recommends
that the table that contents the description of services (SDT, Service Description
Table), was faithful to services that at every moment are contained in the Multiplex.
Even so, it is responsibility of the operator that content of this one and other tables is
updated or that only correct information is contained.
When the BER measurement indicates acceptable reception quality (always to
the left of the QEF level), and the identification information confirms that you have found
the required channel, you will be able to ask for decoding some video and/or audio
service.
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