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VoIP gateway IP400 version 5.01
6.1.6 Voice transmission
Your gateway supports various methods of voice transmission using IP. For calls
between one of your gateway's ISDN interfaces and a VoIP device defined by this
VoIP interface, you can make the relevant definitions in the
Codec configura-
tion
area. Note that calls between two VoIP devices, i.e. from IP to IP, do not
take this setting into account, since the parameters are negotiated directly by the
terminals and their configuration is thus relevant.
Voice coding
There are various ways of encoding voice transmission. Some of the available
encoding options compress speech, others do not. Your gateway supports various
customary voice-encoding schemes, whose properties are described in the follow-
ing table:
Encoding
Band-
width
1
per call
Mini-
mum
delay
2
Properties
G.711A
64 kbit/s
20 ms
No compression, best voice quality
(comparable to digital telephone sys-
tems). Sound digitisation using Euro-
pean encoding
G.711U
64 kbit/s
20 ms
As above; sound digitisation using US
encoding
3
G.726-16
G.726-24
G.726-32
G.726-40
16, 24,
32, 40
kbit/s
20 ms
Intended only in exceptional cases for
fax and modem data.
G.723-53
5.3 kbit/s
30 ms
Good voice quality (comparable to
analogue telephone systems)
G.723-63
6.3 kbit/s
30 ms
Slightly better voice quality than
G.723-53 with slightly greater band-
width.