Supported Codecs - Linksys 900 Series Administrator's Manual

Chapter 1 Introducing Linksys 900 Series IP Phones

Supported Codecs

Negotiation of the optimal voice codec sometimes depends on the ability of SPA900 Series IP
phone to "match" a codec name with the far-end device/gateway codec name. SPA900 Series
IP phones allow the network administrator to individually name the various codecs that are
supported such that the correct codec successfully negotiates with the far-end equipment.
The administrator can select the low-bit-rate codec used for each line. G.711a and G.711u are
always enabled.
phones.
Table 1-3
Codec (Voice Compression
Algorithm)
G.711 (A-law and mµ-law)
G.726
G.729A
G.723.1
When no static payload value is assigned per RFC 1890, SPA900 Series IP phones can support
dynamic payloads for G.726.
Document Version 3.1
Table 1-3 describes the codecs supported by the Linksys SPA900 Series IP
Codecs Supported by Linksys SPA900 Series IP Phones
Description
This very low complexity codec supports uncompressed 64
kbps digitized voice transmission at one through ten 5 ms
voice frames per packet. This codec provides the highest
voice quality and uses the most bandwidth of any of the
available codecs.
This low complexity codec supports compressed 16, 24, 32,
and 40 kbps digitized voice transmission at one through ten
10 ms voice frames per packet. This codec provides high
voice quality.
The ITU G.729 voice coding algorithm is used to compress
digitized speech. Linksys supports G.729. G.729A is a
reduced complexity version of G.729. It requires about half
the processing power to code G.729. The G.729 and G.729A
bit streams are compatible and interoperable, but not
identical.
SPA900 Series IP phones support the use of ITU G.723.1
audio codec at 6.4 kbps. Up to two channels of G.723.1 can be
used simultaneously. For example, Line 1 and Line 2 can be
using G.723.1 simultaneously, or Line 1 or Line 2 can initiate
a three-way conference with both call legs using G.723.1.
Linksys 900 Series IP Phone Administrator Guide
Feature Descriptions
1-7