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G.711 is a default pulse code modulation standard used throughout Internet Protocol private branch exchange vendors and public switched telephone networks. G.711 digitizes analog voice signals to produce output at 64 Kbps.
This ITU Telecommunications Standardization Sector (ITU-T) standard for audio companding is used to encode telephone audio. It’s considered to be the native language of the modern digital telephone network.
G.711 has a tolerance on 8,000 samples per second as 50 parts per million. Nonuniform quantization with 8 bits is used to represent each sample producing a 64 Kbps bit rate.
The two different versions of G.711 are µ-law, which is used primarily in North America, and A-law, which is used in countries outside North America. The difference between the two is based on analog signals being sampled, which is performed in a logarithmic fashion. A-law has more dynamic range than µ-law, and therefore produces a less fuzzy sound because sampling artifacts are better suppressed.
The lower signal values are encoded using more bits while higher signal values require few bits, ensuring that low amplitude signals will be represented while maintaining enough range to encode the high amplitude. The actual encoding does not make use of logarithmic functions. Input range is broken down into segments where each segment uses different intervals between decision values. Most of the segments contain 16 intervals and interval size doubles from one segment to another.
G.711 used along with VoIP gives superior voice quality as no compression is used. It’s the same codec used by public switched telephone networks and integrated services digital network lines. G.711 is supported by most VoIP providers.