G.711.1 Wideband Codec

G.711.1 Wideband Speech Codec

G.711.1 is the wideband extension of the widely deployed ITU-T G.711 speech codec, designed to deliver enhanced voice quality for modern broadband and IP communications while preserving full compatibility with existing G.711-based systems. By introducing advanced encoding techniques, including noise feedback, lower-band enhancement, and high-band audio coding layers, G.711.1 provides significantly improved speech clarity and naturalness compared to traditional narrowband voice communications.

Operating at a 16-kHz sampling rate, G.711.1 produces three bitstreams in three layers. The core layer, operating at 64 kbps, is bitstream interoperable with G.711 (mode 1). Two other layers enhance the fidelity of the output to the original signal. The first one enhances the lower-band part of the signal in a 16-kbps bitstream (mode 2), and the second encodes the higher-band, that is, wideband, part (4000–7000 Hz) in a second 16-kbps bitstream (mode 3). The core layer is always delivered, and either one or both of the upper layers can also be delivered (mode 4), resulting in four possible modes of the G.711.1 codec, as shown in the figure above.

Wideband audio provides high-definition voice quality for telephony calls, and offers better quality than standard digital telephony. It does so by extending the frequency range of audio signals transmitted over telephone lines, resulting in higher quality speech.