Configuring Forward Error Correction - Codec Tieline Gateway User Manual

Configuring Forward Error Correction

24.10
There are two modes of Forward Error Correction (FEC) available in the codec:
1. Tieline FEC: Transmits a secondary stream of audio data packets over a single connection.
2. RFC 2733 compliant FEC (Sessionless connections only): Transmits audio packets over a
separate connection.
FEC is designed to increase the stability of UDP/IP connections in the event that data packets are
lost. FEC works by sending a secondary stream of audio packets over a connection so that if your
primary audio stream packets are lost or corrupted, then packets from the secondary stream can
be substituted to replace them. The amount of FEC required depends on the number of data
packets lost over the IP connection.
Both the local and remote codec FEC settings can be configured in the codec before dialing. FEC
should only be used if link quality displayed on the codec is below S:99 R:99, as it is of no benefit
otherwise. Tieline and RFC2733 compliant FEC settings are outlined in the following table with their
bit rate ratios.
FEC Setting
100%
(Lowest
delay)
50%
33%
25%
20%
10%(Highest
delay)
Off
© Tieline Research Pty. Ltd. 2021
Bit rate Ratios
A simultaneous dual-redundant
stream (1:1 ratio) is sent from
the codec. Twice
connection bit rate is required to
operate the codec using the
100% setting. E.g.
connection is 14,400Kbps, you
will require an additional 14,400
Kbps of bandwidth to allow for
the FEC data stream.
Additional data is sent by FEC
in a ratio of 2:1.
Additional data is sent by FEC
in a ratio of 3:1.
Additional data is sent by FEC
in a ratio of 4:1.
Additional data is sent by FEC
in a ratio of 5:1.
Additional data is sent by FEC
in a ratio of 10:1.
FEC is off in the codec and the
connection bandwidth is equal
to the connection
setting in the codec.
Gateway and Gateway 4 Manual v1.2
Connection Use
Recommended to
be used
the wireless
international
connections.
if your
Recommended for
international
national
connections
Recommended for
national and local
connections.
Recommended for
national and local
connections.
Recommended for
local and
connections.
Recommended for
local and
connections.
Recommended for
wired
bit rate connections
managed T1 & E1
Tieline RFC
FEC 2733
FEC
Yes Yes
over
and
Yes Yes
&
Yes Yes
No Yes
Yes Yes
LAN
No Yes
LAN
Yes Yes
LAN
&
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