When setting up SIP-accounts from some service providers or registering with PBX, whose settings we do not have in the list of server templates you may need to manually specify the list of codecs used and their priority.
Available codecs
Without compression
alaw
alaw/16000
mulaw
mulaw/16000
l16
l16/16000
l16/32000
l16/48000
With compression
gsm
ilbc20
ilbc30
amr
speex
speex/16000
speex/32000
isac/16000
isac/32000
gsm-efr
opus
g722/16000
g729
The digits after / are the sampling rate. If not specified, the standard 8kHz frequency is used. The exception is the Opus codec: it operates at 48 kHz.
mulaw is the telephony standard for the USA, alaw for Europe. /16000 are their high quality versions.
Opus is a modern, high-quality codec used by Telegram for calls. Opus is resistant to network loss.
L16 and variations via / are raw codecs. L16 is not loss tolerant and requires a good quality connection, so works best when connected directly to a WATS.
Example of setting a codec set
opus,g722/16000,alaw,mulaw,g729
Values are separated by commas, no spaces, case insensitive.