User Manual

Configuring Audio Features
303
Codec
Algorithm
Reference
Bit Rate
Sample
Rate
Packetization
Time
G726-40
G.726
RFC 3551
40 Kbps
8 Ksps
20ms
G723_53/
G723_63
G.723.1
RFC 3551
5.3kbps
6.3kbps
8 Ksps
30ms
iLBC
iLBC
RFC 3952
15.2 Kbps
13.33 Kbps
8 Ksps
20ms
30ms
Packetization Time
Ptime (Packetization Time) is a measurement of the duration (in milliseconds) of the audio data
in each RTP packet sent to the destination, and defines how much network bandwidth is used
for the RTP stream transfer. Before establishing a conversation, codec and ptime are negotiated
through SIP signaling. The valid values of ptime range from 10 to 60, in increments of 10
milliseconds. The default ptime is 20ms. You can also disable the ptime negotiation.
Codecs and priorities of these codecs are configurable on a per-line basis. The attribute “rtpmap”
is used to define a mapping from RTP payload codes to a codec, clock rate and other encoding
parameters.
The corresponding attributes of the codec are listed as follows:
Codec
Configuration Methods
Priority
RTPmap
G722
Configuration Files
Web User Interface
1
9
PCMU
Configuration Files
Web User Interface
2
0
PCMA
Configuration Files
Web User Interface
3
8
G729
Configuration Files
Web User Interface
4
18
G723_53
Configuration Files
Web User Interface
0
4
G723_63
Configuration Files
Web User Interface
0
4
G726-16
Configuration Files
Web User Interface
0
103
G726-24
Configuration Files
Web User Interface
0
104