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Notes:
– Increasing the voice quality is usually also
associated with an increase in the band-
width required.
– The values for the voice quality are set at
the factory to ensure the voice quality is
generally acceptable. You should therefore
only change the preset values if the voice
quality seems to you to be too poor or if you
wish to reduce the bandwidth required at
the expense of the voice quality (e.g. for
parallel connections to the Internet).
Execution time of voice packets
The execution time determines the delay
between the sender speaking and the
recipient hearing what has been said. A
long delay is experienced as disruptive
when making calls. The execution time
consists of the following:
u
the time required to digitalise the
voice, to packetise it into data packets
and to convert the voice packets into
voice. You can influence the time
required through the choice of
(coder-decoder) used.
Both parties involved in the telephone
connection (caller/sender and recipi-
ent) must use the same Codec. The
Codec is negotiated between the
sender and the recipient when estab-
lishing a connection.
u
The time the voice packets spend in the
Internet, essentially consisting of the
time the voice packets wait in the SIP
routers when there is heavy traffic. To
improve the waiting time, you can
request preferred handling of the data
packets in the Internet – a
– and reduce the size of the
Service
voice packets
(RTP Packet
packets generally mean a longer execu-
tion time.
Silence Suppression
With Silence Suppression activated, hardly
any data packets are transmitted from the
sender during pauses in the conversation.
At the recipient's end, "synthetic" noise is
created instead during pauses, which is
intended to replace the background
noises.
Silence Suppression saves transmission
capacity, but can reduce the voice quality.
Setting the voice quality
¤
¤
¤
¤
Codec
¤
Quality of
Size). Large
Open the following Web page:
¢
Admin
Audio
Settings.
Open the
Codec
list and select Codec.
G.711 (default setting), G.723,
G.729A/B and G.722 are available for
selection. For information on the
Codecs, see the Online Help for the
Web configurator.
Open the
RTP Packet Size
the packet
size.
If relevant, click on
to activate the function.
Click on Apply.
Note:
Codec
If you select a
as "preferred" and the
receiving device does not support this Codec,
then a different Codec (lower quality) is nego-
tiated. The connection is established.
If you select a Codec as "only" and the receiv-
ing device does not support this Codec, the
connection is not established. An appropriate
message will be displayed on the handset.
Handset settings
list and select
Silence Suppression
89
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