Albalá Ingenieros AGW3000C01, Руководство пользователя

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Albalá Ingenieros | Manual AGW3000C01
4.3.3. Operation in manual mode
Manual mode is useful for maintenance of the installation. The user selects the input
to be used and no switching will occur even if an error occurs in that input. Input
selection is stored in non-volatile memory and is recalled in case of a power supply
failure.
Selection of the input in manual mode is done using the SELECT button in the INPUT
SELECTION box on the front panel. Long presses are used to select the output to be
used and, once selected, the LED corresponding to the selected output will blink. Short
presses of the button cycles through the inputs that will be assigned to the selected
output. Note that if one or more inputs are deactivated then they cannot be selected
in this manner. However if the inputs are selected using the module's control
software then even deactivated inputs can be selected.
The elements within the ALARM box on the front panel operate in the same fashion as
in automatic mode.
4.4. Description of the TS over IP encapsulators/de-encapsulators
Several different protocols exist for encapsulation of DVB transport streams over IP.
• Protocol UDP: This is the simpler protocol that can be used, but it is the least robust.
UDP consists of grouping up to seven TS packets and transmitting them within one
UDP packet. This protocol does not detect dropped packets nor packets arriving out of
sequence.
• Protocol RTP: This protocol is similar to UDP with respect to the way in which packets
are grouped for transmission but adds a header that includes a continuity flag for
detection of dropped packets and packets received out of sequence along with a
timestamp to facilitate elimination of jitter introduced by the network. When using the
RTP protocol a single frame (FEC Type A) or two frames (FEC Type B) of auxiliary data
can be sent in order to correct errors or dropped packets. When using the RTP protocol
the AGW3000C01 can be configured to substitute dropped and non-recoverable
packets of the TS with null packets.
4.5. System latencies
When transporting DVB frames over ASI interfaces the latency introduced due to
serialization and de-serialization is minimal in comparison to other delays that may exist
in the system. During encapsulation of the DVB over IP frames mechanisms are
employed to correct errors and absorb any jitter generated by the IP networks. These
mechanisms introduce delays in the transport of the frames that may on occasion need
to be accounted for. This section describes the latencies introduced for each of the
modules within the AGW3000C01:
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