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Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
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CODEC is an abbreviation of COmpress-DECompress, capable of coding or decoding a
digital data stream or signal by implementing an algorithm. The object of the algorithm
is to represent the high-fidelity audio signal with minimum number of bits while retaining
the quality. This can effectively reduce the frame size and the bandwidth required for
audio transmission.
The audio codec that the phone uses to establish a call should be supported by the SIP
server. When placing a call, the IP phone will offer the enabled audio codec list to the
server and then use the audio codec negotiated with the called party according to the
priority.
The following table lists the audio codecs supported by each phone model:
Phone Model Supported Audio Codecs Default Audio Codecs
SIP-T48G/T46G/T42
G/T41P/T29G/CP86
0 G722, PCMA, PCMU, G729, G726-16,
G726-24, G726-32, G726-40, iLBC,
G723_53, G723_63
G722, PCMA, PCMU,
G729
SIP-T40P/T27P/T23P/
T23G/T21(P)
E2/T19(P) E2
G722, PCMA, PCMU, G729, G726-16,
G726-24, G726-32, G726-40, iLBC
G722, PCMA, PCMU,
G729
SIP-T27G
G722, PCMA, PCMU, G729, G726-16,
G726-24, G726-32, G726-40, iLBC,
Opus
G722, PCMA, PCMU,
G729
SIP VP-T49G
G.722.1c(48kb/s), G.722.1c(32kb/s),
G.722.1c(24kb/s), G.722.1(24kb/s),
G722, PCMU, PCMA, G729, G726-16,
G726-24, G726-32, G726-40, iLBC,
G723, Opus
G.722.1c(48kb/s),
G.722.1c(32kb/s),
G.722.1c(24kb/s),
G.722.1(24kb/s),
G722, PCMU, PCMA,
G729
The following table summarizes the supported audio codecs on IP phones:
Codec Algorithm Reference Bit Rate
Sample
Rate
Packetization
Time
G.722.1c
G.722.1
RFC 5577 48 Kbps 32 Ksps
20ms
G.722.1c RFC 5577 32 Kbps 32 Ksps
20ms
G.722.1c RFC 5577 24 Kbps 32 Ksps 20ms
G.722.1 G.722.1 RFC 5577 24 Kbps 16 Ksps 20ms
G722 G.722 RFC 3551 64 Kbps 16 Ksps
20ms
PCMA G.711
a-law
RFC 3551 64 Kbps 8 Ksps 20ms