In VoIP it is a voice compression-decompression algorithm that reduces the bandwidth required for the audio signal to allow a more effective use of the infrastructure. The CODEC used isn’t that relevant today as it used to be with DSL, that caused many call quality issues. On the UC Portal, we have 3 options (High Bandwidth – G.711, Normal Bandwidth – G.722, Low Bandwidth – G.729). G711 is our preferred Codec.