Codecs
The following codecs are supported:
| Codec | Models | Firmware | Bitrate | Sampling Rate | Notes |
|---|---|---|---|---|---|
G.711 a-law | A20, A22, A25, A30 | All released firmware | 64000 bps | 8kHz, Narrowband | |
| G.711 u-law | A20, A22, A25, A30 | All released firmware | 64000 bps | 8kHz, Narrowband | |
| G.726 | A20, A22, A25, A30 | All released firmware | 32000 bps | 8kHz, Narrowband | |
| iLBC, 30ms | A30 | All released firmware | 13333 bps | 8kHz Narrowband | |
| Opus | A30 | All released firmware | 12000 bps | 8kHz Narrowband | Only one channel is supported at a time. Users should enable at least one other codec when using Opus to allow three-way calling. |
| G.729a | A20, A22, A25, A30 | All released firmware | 8000 bps | 8kHz, Narrowband | |
| G.722 | A20, A22, A25, A30 | All released firmware | 64000 bps | 16kHz, Wideband | |
| Opus | A30 | All released firmware | 20000 bps | 16kHz, Wideband | Only one channel is supported at a time. Users should enable at least one other codec when using Opus to allow three-way calling. |
In order to limit MTU size for UDP-based SIP signaling, Digium phones only enable a limited subset of these codecs by default. Use of some codecs may require enabling them, which can be done via web UI or remote configuration files.