G.711

G.711

Pulse code modulation (PCM) of voice frequencies
Status	In force
Year started	1972
Latest version	(02/00) February 2000
Organization	ITU-T
Related standards	G.191, G.711.0, G.711.1, G.729
Domain	audio compression
Website	https://www.itu.int/rec/T-REC-G.711

G.711 is a narrowband audio codec originally designed for use in telephony that provides toll-quality audio at 64 kbit/s. It is an ITU-T standard (Recommendation) for audio encoding, titled Pulse code modulation (PCM) of voice frequencies released for use in 1972.

G.711 passes audio signals in the frequency band of 300–3400 Hz and samples them at the rate of 8000 Hz, with the tolerance on that rate of 50 parts per million (ppm).

It uses one of two different logarithmic companding algorithms: μ-law, which is used primarily in North America and Japan, and A-law, which is in use in most other countries outside North America. Each companded sample is quantized as 8 bits, resulting in a 64 kbit/s bit rate.

G.711 is a required standard in many technologies, such as in the H.320 and H.323 standards.^[1] It can also be used for fax communication over IP networks (as defined in T.38 specification).

Two enhancements to G.711 have been published: G.711.0 utilizes lossless data compression to reduce the bandwidth usage and G.711.1 increases audio quality by increasing bandwidth.