Cisco SPA525G Administration Guide - Page 121

Configuring Security, Quality, and Network Features Ensuring Voice Quality 6 The administrator can select the low-bit-rate codec used for each line. G.711a and G.711u are always enabled. The following table shows the codecs supported by Cisco IP phones. The third column shows the voice quality Mean Opinion Score (MOS), with a scale of 1-5, in which higher is better. Codec (Voice Compression Algorithm) G.711 (A-law and u-law) G.726 G.729 and G.729A G.723.1 G.722 Complexity and Description MOS Score Very low complexity. 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. 4.5 Highest voice quality Low complexity. Supports compressed 16, 24, 32, and 40 kbps digitized voice transmission at one through ten 10 ms voice frames per packet. When no static payload value is assigned per RFC 1890, Cisco IP phones can support dynamic payloads for G.726. 4.1 (32 kbps) NOTE G.726 is supported only for 32kbps on the SPA525G. G.729A low-medium complexity. G.729 medium 4 complexity. G.729A requires about half the processing power of G.729. The G.729 and G.729A bit streams are compatible and interoperable, but not identical. High complexity. Cisco IP phones support the use of 3.8 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 threeway conference with both call legs using G.723.1. NOTE G.723.1 is not supported on the 525G or WIP310. Supported on the SPA525G only. Only one G.722 call at a time is allowed. If a conference call is placed, a SIP re-invite message is sent to switch the calls to narrowband audio. 4.3 (approx) Cisco SPA and Wireless IP Phone Administration Guide 119