Overview of G.711

 

 

G.711 is an ITU-T standard for audio companding. It is primarily used in telephony. The standard was released for usage in 1972. Its formal name is Pulse code modulation (PCM) of voice frequencies. It is required standard in many technologies, for example in H.320 and H.323 specifications. It can be also used in one of methods for fax communication over IP networks (as defined in T.38 specification).

 

G.711 represents logarithmic pulse-code modulation (PCM) samples for signals of voice frequencies, sampled at the rate of 8000 samples/second.
 

G.711.0 (G.711 LLC) - Lossless compression of G.711 pulse code modulation was approved by ITU-T in September 2009.[1][2] It gives as much as 50 percent reduction in bandwidth use.[3]
 

G.711.1 is an extension to G.711, published as ITU-T Recommendation G.711.1 in March 2008. Its formal name is Wideband embedded extension for G.711 pulse code modulation.[4][2]
 

G.711, also known as Pulse Code Modulation (PCM), is a very commonly used waveform codec. G.711 uses a sampling rate of 8,000 samples per second, with the tolerance on that rate 50 parts per million (ppm). Non-uniform quantization (logarithmic) with 8 bits is used to represent each sample, resulting in a 64 kbit/s bit rate. There are two slightly different versions; μ-law, which is used primarily in North America, and A-law, which is in use in most other countries outside North America.

 

Exerpt taken from Wikipedia