ITU-T Standard Vocoders
G.711
The algorithm implemented is the
ITU-T G.711 recommendation, fixed rate audio coder. The encoder compresses
linear-PCM (Pulse Code Modulated), narrowband audio input data, at a sample
rate of 8kHz, to 64 000 bps, using non-linear quantisation. G.711 is a simple
algorithm, using two selectable logarithmic coding laws, A-law (European standard)
and (mu-law (US standard). It is often used at rates less than 64 000 bps,
namely 56 000 and 48 000 bps with a slight reduction in speech quality. This
allows an 8 000 bps or 16 000 bps auxiliary data channel.
G.711 is the mandatory minimum standard for all ISDN terminal equipment.
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