
TOPEX MobiLink
IP
Preliminary Manual
Codec priority
MobiLinkIP supports several audio codecs, currently
G.711 (both A-law and u-law), 723 and 729. There
are four boxes, with decreasing priorities, from 1
down to 4. For each one, one may assign a codec,
or select “none”. Generally one should enter the
codec G.711 on the first place, either with A-Law for
Europe or u-law for North America, followed by
G.729. G.711 provides good voice quality and works
well with in-band DTMF.
If the IP-PBX or the SIP-telephones that will be connected with MobiLinkIP make use of different
codecs, one should set the “Codec Propriety” field accordingly.
RTP Packet Length
It lets you establish the value for packetization time (in
milliseconds) for each codec. It is usually set to 20, but it may be
as long as 30 msec or as short as 5 msec. Increasing the
packetization time reduces the packetization overhead, but
increases the latency.
Voice VAD
Enables or disables the "Voice Activity Detection", by default this
feature is disabled.
Typical voice conversations can contain up to 35 to 50 percent silence. On VoIP networks, both
conversation and silence is packetized. If VAD is enabled, the equipment sends out RTP packets only
when voice is detected, thus decreasing bandwidth by 30-50 %. This way the MobiLinkIP will send
voice packets only when it has voice input. When it detects silence on RTP, it will send a “silence
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