In addition to packet delays, codecs also add some delay in the network. The delay of the G.711 codec is minimal. However, the G.729 codec, for example, adds approximately 10 ms of algorithmic delay in each direction, another 5 ms look-ahead, and signal processing delays.
The compression algorithm in G.723.1 uses multiple blocks, called frames, of 30 ms voice samples per packet, resulting in an increased latency over codecs configured to use 20 ms or less samples per packet.
