VoIP-Codecs

G.711 Codec

G.711 Codec

G.711 is a codec that was introduced by ITU in 1972 for use in digital telephony. The codec has two variants: A-Law is being used in Europe and in international telephone links, uLaw is used in the U.S.A. and Japan.

  • G.711 uses a logarithmic compression. It squeezes each 16-bit sample to 8 bits, thus it achieves a compression ratio of 1:2.
  • The bitrate is 64 kbit/s for one direction, so a call consumes 128 kbit/s.
  • G.711 is the same codec used by the PSTN network, hence it provides the best voice quality. However it consumes more bandwidth than other codecs.
  • It works best in local area networks where we have a lot of bandwidth available.

Bandwidth consumption for G.711 codec

Codec Voice Payload Size (ms) Voice Payload Size (Bytes) Comments
G.711 20 ms (default) 160 Bytes Notice that the codec bit rate is always maintained. For example: G.711 codec = [240 bytes * 8(bits/bytes)] / 30 ms = 64 Kbps
30 ms 240 Bytes