Vislink Strata RX, Техническое справочное руководство

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Link Quality D-7
Strata RX
Technical Reference Manual
least robust BW setting.
Note
that the receiver must be
manually
set to match the BW
setting of the transmitter.
D.4.5 BER
When the receiver applies its error corrections to the incoming
data, it counts both the total number of errors it has detected and
the number it cannot correct.
• The Pre-Viterbi BER measures the
total
number of errors
the FEC algorithm attempted to correct. This BER is
defined as
# Errors Detected / # Bits Received
• The Post-Viterbi BER measures only the errors the FEC
algorithm was
not
able to correct. This BER is defined as
# Errors Not Corrected / # Bits Received
As signal quality degrades, the Pre-Viterbi BER will increase.
This indicates the System is detecting more errors. However, the
FEC algorithm will be able to correct these errors, and the Post-
Viterbi BER will be maintained at 0. Video and audio will be
undisturbed.
As the signal continues to degrade, the Pre-Viterbi BER will
continue to increase. At some point the FEC algorithms will
reach the limit of errors they can correct. The uncorrected errors
will then appear in the Post-Viterbi BER. These Post-Viterbi
errors are a warning sign, even though the video may still be
acceptable.
If the Post-Viterbi BER becomes too large, the MPEG decoder
will be unable to make sense of the data, and video will suddenly
be lost.
The BER at which this occurs will vary depending on the design
of the MPEG decoder and the location of the errors in the data
stream.