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.|