Linksys SPA 900 SERIES manual Supported Codecs, Algorithm Description

Chapter 1 Introducing Linksys IP Phones

Feature Descriptions

If the Linksys IP phone is currently using a lower priority proxy server, it periodically probes the higher priority proxy to see whether it is back on line, and attempts to switch back to the higher priority proxy whenever possible.

Supported Codecs

Negotiation of the optimal voice codec sometimes depends on the ability of Linksys IP phone to “match” a codec name with the far-end device/gateway codec name. Linksys 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. Table 1-3describes the codecs supported by the Linksys IP phones.

Table 1-3 Codecs Supported by Linksys IP Phones

Codec (Voice Compression
Algorithm)	Description
G.711 (A-law and mµ-law)	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.
G.726	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.
G.729A	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.
G.723.1	Linksys 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.

When no static payload value is assigned per RFC 1890, Linksys IP phones can support dynamic payloads for G.726.

	Linksys IP Phone Administrator Guide
1-6	Firmware Version 5.1