G.728

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 bit/s. Also network signalling goes through. The complexity of the codec is 30 MIPS. 2 kBytes of RAM is needed for codebooks.