DSX IP keysets support G.711, G.722, and G.729 CODEC types, and should normally connect using the CODEC listed first in the profile. The additional CODECs are for third-party SIP SLT compatibility. When setting up the connection, the system may have to work downward through the profile's CODEC list to find an acceptable setting. If the third-party SIP SLT can't negotiate a compatible CODEC, it won't connect.
The following table provides a very basic performance comparison of the supported CODEC types. For more details, see Cisco's Voice Over IP - Per Call Bandwidth Consumption site.
| Basic CODEC Comparison | |||
| CODEC | Bit Rate (Kbps)1 | Mean Opinion Score (MOS)2 | Bandwidth Requirement (Ethernet)3 |
| G.711 | 64 Kbps | 4.4 | 87 Kbps |
| G.726 | 32 Kbps | 3.9 | 55.2 Kbps |
| G.729AB | 8 Kbps | 4.2 | 31 Kbps |
| G.723 | 6.3 Kbps | 4.0 | 22 Kbps |
| G.722 | 64 Kbps | 4.2 | 80 Kbps |
| ILBC | 15 Kbps | 4.1 | 27.7 Kbps |
| 1 This is the rate at which audio is sampled during encoding into digital signals. In general, higher sample rates yield better voice quality. | |||
| 2 MOS is a method of rating voice call quality as judged by actual humans (i.e., not calculated). A rating of 1 is poor; a rating of 5 is excellent. An MOS rating of less than 4 is often perceived as poor speech quality. | |||
| 3 Bandwidth is a per-call network utilization statistic. You need enough bandwidth in your network to support the likely number of simultaneous IP calls. | |||
| Option | Description |
|---|---|
| 00 | [Default] None |
| 01 | G.711 |
| 02 | G.726 |
| 03 | G.729AB |
| 04 | G.723 |
| 05 | G.722 |
| 06 | ILBC |