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VN-Matrix 300 • System Conguration 40
ANC Panel
Provides for control and configuration of the ancillary data channels.
Selecting the Audio group
There are 16 audio channels present in the SDI/HDSDI/3G SDI video transport. These are
arranged in 4 groups each of 4 channels. The VN-Matrix 300 units can transport 1 group
(4 audio channels). The required audio group is selected here. The groups are presented as
channel pairs as described below.
z Channel pair 1: Group 1, channels 1&2
z Channel pair 2: Group 1, channels 3&4.
z Channel pair 3: Group 2, channels 1&2
z Channel pair 4: Group 2, channels 3&4.
z Channel pair 5: Group 3, channels 1&2
z Channel pair 6: Group 3, channels 3&4.
z Channel pair 7: Group 4, channels 1&2
z Channel pair 8: Group 4, channels 3&4.
The indicator to the right of the list showing each channel pair is green if that audio group is
present in the SDI source.
Selecting either of the check boxes associated with a group will automatically enable both of
the channel pairs in that group. It is not possible to select fewer than 2 channel pairs.
FEC Panel
Forward error correction may be applied to the ancillary data. This protects against packet
loss when the ancillary data is transported across a network.
Forward Error Correction
Forward error correction may be applied to the Ancillary data to protect against errors
caused by packet loss when the data is transported over a network. Forward Error Correction
(FEC) enables the decoder to recreate data that has been lost or corrupted without the need
for retransmission. The FEC data is sent separate from the image and ancillary data.
The level of FEC can be set to protect against different levels of data loss. This produces a
corresponding change in the amount of data that is transported and thus, the bit rate is
increased or decreased in proportion to the amount of FEC applied.
PRO-MPEG COP3
The error correction scheme employed on the VN-Matrix 300 product range is implemented
using the recommendations of PRO-MPEG COP3.
Row and Column FEC
The FEC may be applied as either column or column and row.
z Column FEC is used to protect against burst packet losses, providing that the burst of
packet losses are not in the same row. Column FEC is known as 1D (dimension) FEC, as
correction data is only calculated on one dimension.
z Row FEC is used to protect against the loss of a single packet. It is the simplest method
of protection and results in the lowest overhead in terms of bit rate and latency.
However, it is not able to handle consecutive (burst) burst packet loss.