G.723.1 is a standard for digital communications that employs 16-bit pulse-code modulation (PCM) at 5.3 or 6.3 kilobits per second (Kbps) with an input sample rate of 8 kilohertz (kHz). The encoding is done in frames having a duration of 30 milliseconds (ms). The look-ahead is 7.5 ms so the total algorithmic delay is 37.5 ms. The compression ratio can be as high as 12:1. In conjunction with voice activation detection (VAD), this provides exceptionally narrow signal bandwidth.
G.723.1 offers the capability for full-duplex or half-duplex modes for multichannel operation and can be useful in multimedia systems that incorporate digital signal processing (DSP). In voice communications, the audio quality is lower than that afforded by more robust codecs such as G.711. Perhaps because of this, G.723.1 has been supplanted by other standards for consumer Voice over Internet Protocol (VoIP).
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