Abstract: The voice signal s(n) is filtered through a short-term predictive filter (13) tuned with PARCOR derived coefficients computed over a pre-emphasized s(n), said filter (13) providing a short-term residual r(n). Said r(n) signal is then processed through a first Cod-Excited/Long-Term Predicative coder providing first couples of table address and gain data (k1, gl)'s. An error signal r'(n) is then derived by subtracting coded/decoded data from uncoded data. Then said error signal is processed through a second Code-Excited/Long-Term Predictive coder providing second couples of data (k2, g2)'s. Full rate coding is achieved by multiplexing both couples (k1, gl)'s and (k2, g2)'s into a multi-rate frame; while switching to a lower rate is achieved through a mere delation of (g2, k2)'s from the full rate frame.

Abstract: This low bit rate voice encoding involves short-term predictive filtering the voice signal s(n) using partial correlation related coefficients derived from pre-emphasized s(n), and deriving a short term signal r(n); then deriving a long-term residual signal e(n) by subtracting a delayed synthesized short term b.r'(n-31 M) from said r(n); and code excited encoding e(n) into codeword references k's and associated gains G's.