In communications engineering, the term "Codec" is a technical term for the "compression/decompression" of data.  Codecs vary in the sound quality, the bandwidth required, the computational requirements, etc.

IPComms supports two Codec types: G.711 and G.729.

G.729
G.729 has a 8k bitrate.  it provides good audio quality with low bandwidth requirements. it is the most commonly used codec in VoIP calling.

G.711
G.711 has a 64K bitrate and is best used where there is a lot of bandwidth available.