G711 and G729 Explained

G.711 is the highest quality codec that all of the VOIP equipment and providers support.

G.729 has a theoretical MOS rating of 3.9 where G.711 has a theoretical MOS score of 4.1. That is on a jitter-free, packet-loss-free network.

The advantage of G.729 is that it is more compressed and requires less bandwidth. That also makes it more fragile because a missing or late packet messes up the packets after it. Jitter and packet loss causes damage to the G.729 audio much more quickly than G.711.

Most of the time it is jitter and/or packet loss that is causing audio problems rather than bandwidth. That is, it is rare to have a low-loss, low-jitter network connection where the first eight calls are perfect and the ninth call makes them all fail.

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