Improvements in 2.4 kbps high-quality speech coding

An algorithm for 2.4 kb/s speech coding is described. The main problem addressed is the coding of voiced speech. A way of coding the pitch structure is introduced. Compared with traditional coding schemes, it results in a better compromise between bit allocation for short-term quantization and residual coding. The coder uses vector quantization of the short-term parameters (line spectrum frequencies). The residual is lowpass filtered to obtain the baseband signal. Unvoiced frames are coded by means of a method based on repetition and interpolation of pitch pulses. The method exploits the high correlation between pitch pulses. Harmonic postfiltering is applied to obtain an improved high-frequency regeneration