Code-excited linear predictive coder and decoder with conversion filter for converting stochastic and impulsive excitation signals

摘要

A code-excited linear predictive coder or decoder for a speech signal has an adaptive codebook (105), a stochastic codebook (106), and a pulse codebook (107). A constant excitation signal (ec) is obtained by choosing between a stochastic excitation signal (es) selected from the stochastic codebook and an impulsive excitation signal (ep) selected from the pulse codebook. The constant excitation signal is filtered to produce a varied excitation signal more closely resembling the original speech signal. The varied excitation signal is combined with an adaptive excitation signal (ea) selected from the adaptive codebook to produce a final excitation signal (e) which is filtered to generate a synthesized speech signal. The final excitation signal (e) is also used to update the adaptive codebook.