Codec converts an analog audio signal (your voice) into compressed digital form for transmission (VoIP) and then back into an uncompressed audio signal for replay. In order to achieve this, codec converts each tiny sample into digitized data and compresses it for transmission. Codec’s selection directly impacted the call quality so you have to be careful while choosing a codec in the priority list.
VND PBX supports quite a few codecs but we recommend you to use the following three.
- ITU G.729 – 8 Kbps, 10ms frame size
- ITU G.711 – 64 Kbps, sample-based. Comes in two flavours: A-law and mu-law
You can read more about codecs and their bandwidth requirement.