G711

G.711 is an ITU-T standard for PCM audio coding used in telephony. It defines two companding algorithms, A-law and μ-law, which shape the dynamic range of digital voice samples so they can be encoded efficiently as 8-bit values at an 8 kHz sampling rate. The resulting data rate is 64 kilobits per second, making G.711 a fixed-bandwidth, low-complexity codec suitable for traditional telephone networks and VoIP gateways that require compatibility with the public switched telephone network (PSTN).

In G.711, voice signals are represented by 8-bit codes derived through either A-law or μ-law companding. A-law is predominantly used in Europe and parts of Asia, while μ-law is common in North America and Japan. Both methods provide different dynamic-range mappings but achieve similar perceptual quality at the same nominal bitrate. In practice, G.711 is transported in VoIP systems as RTP payloads labeled PCMU for μ-law and PCMA for A-law.

Usage and characteristics: G.711 is widely deployed due to its simplicity and very low processing requirements, resulting in minimal latency. It is often chosen for interoperability with legacy telephone systems and for scenarios where maximum compatibility is essential. However, because it does not compress voice beyond 8-bit PCM, it consumes more bandwidth than many modern codecs, particularly those designed for wideband or compressed speech.

Related notes: G.711 remains a foundational codec in telecommunication, frequently used as a baseline for quality and as a fall-back option in mixed networks. It is complemented by newer standards such as wideband and high-efficiency codecs for applications demanding lower bitrate without significant loss of speech intelligibility.