Tieline ViA User Manual page 159

The four FEC settings are outlined in the following table with their bit rate ratios.
FEC Setting
100%
(Lowest
delay)
50%
33%
20% (Highest
delay)
Off
Important Note: FEC can only be programmed for use with the Music and MusicPLUS
algorithms.
How does FEC work?
If you configure a FEC setting of 20% and you are losing one packet in every five sent, the lost
packet will be replaced by FEC to maintain the quality of the connection. If you are losing more
packets than this, say one in three, it will be necessary to increase the FEC setting to 33% to
compensate.
Note: There is an inverse relationship between FEC settings and the jitter-buffer millisecond setting
that you use for IP connections.
So why not use 100% FEC every time? The answer is because you need twice the bit rate to
achieve full redundancy and depending on the link conditions, this could potentially cause more
dropouts because of network congestion than it fixes. Here is a simple rule to remember: Your
maximum uplink speed is all the bandwidth you have to play with. As a rule of thumb, try not to
© Tieline Pty. Ltd. 2017
Bit rate Ratios
A simultaneous dual-redundant
stream (1:1 ratio) is sent from the
codec. Twice the connection bit
rate is required to operate the
codec using the 100% setting.
E.g. if your connection
14,400kbps, you will require an
additional 14,400
bandwidth to allow for the FEC
data stream.
Additional data is sent using FEC
in a ratio of 2:1.
Additional data is sent using FEC
in a ratio of 3:1.
Additional data is sent using FEC
in a ratio of 5:1.
FEC is off in the codec and the
connection bandwidth is equal to
the connection bit rate setting in
the codec.
ViA User Manual v2.0
Connection Use
Recommended to be used over
wireless
connections.
is
kbps of
Recommended for international &
national connections
Recommended for national and local
connections.
Recommended for local and LAN
connections.
Recommended
connections & managed T1 & E1
connections for STLs that have
connections that aren't shared &
have quality of service (QoS).
159
and international
for wired LAN