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|