Dallas Delta Corporation Pty.Ltd.
Page 8
Voice
In this section, select the order and preferred CODEC’s, plus
sent for each.
Also, select the options that effect the different codecs used and DTMF sending method and
payloads.
the amount of frames per packet to
When selecting the codecs consider the data rate that will be required by your network. As a
guild the list here show the data bit rate required for each codec, if the network is via a low
speed ADSL then the PCMu/a may not be a suitable choice.
Table 1. Codec comparison
Codec
bit rate (kbit/s)
G.711(PCMu /a)
64
G726-32
32
GSM
13.2
iLBC 20ms
15.2
iLBC 30ms
13.3
Speex
2.15 - 24.6
G.729
8
If the iLBC or SPEEX codecs are used, then set the following for each,
a)
iLBC
codec, select the frame size your network requires to 20mS or 30mS.
b)
SPEEX
codec, select a suitable bit rate for best quality available, the range
is from 2.15kBits/s to 24.6kBits/s.
The
Frames per TX
selects how many blocks of data (10mS segments) are transmitted with
each packet sent over the network. (note the higher the number, the more the delay), 2 - 4 is
recommended.
The
Send DTMF type
selects how the unit will send
DTMF
digits over the network (only
required for unit fitted with a front panel keypad and if digits are dialled during a conversation).
The remaining options set the payload required for each protocol and it is recommend that
the default values be used.
