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G.728 is a ITU-T standard for speech coding operating at 16 kbit/s. Techology used is LD-CELP, Low Delay Code Excited Linear Prediction. Delay of the codec is only 5 samples (0.625 ms). The linear prediction is calculated backwards with a 50th order LPC filter. The excitation is generated with gain scaled VQ. The standard was finished in 1992 in the form of algorithm exact floating point code. In 1994 a bit exact fixed point codec was released. G.728 passes low bit rate modem signals up to 2400 bps. Also network signalling goes through. The complexity of the codec is 30 MIPS. 2 kBytes of RAM is needed for codebooks.
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