Operation Manual

83
 FEC Mode: If you select Column Only, the B264 will send a single FEC flow,
corresponding to the column protection data, using a UDP port number corresponding to
the media UDP port number plus 2. If you select Row and Column, the B264 will send
two FEC flows, the first corresponding to the column protection data, and the second
corresponding to the row protection data. The row protection data will be sent using a
UDP port number corresponding to the media UDP port number plus 4. Note that not all
receivers support Row and Column mode; such receivers will only use the FEC Column
data and discard the FEC Row data.
 Columns: Number of columns in the FEC matrix. This variable must be between 1 and
20 if FEC Mode is set to Column Only, and between 4 and 20 if it is set to Row and
Column.
 Rows: Number of rows in the FEC matrix. This variable must be between 4 and 20.
 FEC Overhead: This field is updated as configuration is entered, and contains the
overhead for the selected FEC configuration. Note that not all parameter changes cause
the overhead to change. The FEC overhead is the sum of a Column overhead and a Row
overhead (which is zero if FEC Mode is Column Only). The overhead is a function of
the settings, as follows:
o Increasing the number of columns decreases the Row overhead (if enabled) and
does not change the Column overhead.
o Increasing the number of rows does not change the Row overhead and
decreases the Column overhead.
o Decreasing the number of rows and columns has the opposite effect as the
previous items.
The following constraints apply to the FEC function:
 The number of rows must be between 4 and 20.
 The number of columns must be between 1 and 20 for Column Only mode, or between 4
and 20 in Row and Column mode.
 The size of the FEC matrix (product of the number of rows and the number of columns)
must not exceed 100.
The user interface will not allow invalid configurations to be entered, and will automatically
make parameter adjustments as required. Examples: