What is G.711?
G.711 is a standard pulse code modulation standard used by Internet Protocol telephone exchanges and public switched telephone networks. G.711 digitizes analog voice signals to produce 64 Kbps output.
This ITU Telecommunications Standardization Sector (ITU-T) standard for audio companding is used to encode telephone audio. It is considered the mother tongue of the modern digital telephone network.
G.711 has a tolerance of 8,000 samples per second as 50 parts per million. A non-uniform 8-bit quantization is used to represent each sample that produces a bit rate of 64 Kbps.
The two different versions of G.711 are the μ-law, which is mainly used in North America, and the A-law, which is used in countries outside of North America. The difference between the two is due to the sampling of analog signals, which is performed logarithmically. A-Law has a wider dynamic range than μ-Law and therefore produces a less fuzzy sound because it suppresses sampling artifacts better.
The lower signal values are encoded using more bits while the higher signal values require fewer bits, ensuring that low amplitude signals are represented while maintaining sufficient area to encode the high amplitude. The actual coding does not use any logarithmic functions. The input area is divided into segments, with each segment using different intervals between the decision values. Most segments contain 16 intervals and the interval size doubles from one segment to another.
G.711 is used in conjunction with VoIP and offers superior voice quality as no compression is used. It is the same codec used by public switched telephone networks and digital lines for integrated services. Most VoIP providers support G.711.