Abstract: A method and apparatus for coding successive pitch periods of a speech signal. Based on a priori knowledge of statistical properties of successive speech periods, a shaped lattice structure is designed to cover the most probable points in the pitch space. The codebook index search starts with finding an open-loop estimate in the pitch space considering all dimensions and refining the open-loop estimate in a closed-loop search separately in each dimension based on the shaped lattice structure. The closed-loop search for the first subframe is for obtaining an absolute pitch period or a delta pitch while the closed-loop search for each of the other subframes is for obtaining a delta pitch for the respective subframe.

Abstract: A method and apparatus for coding successive pitch periods of a speech signal. Based on a priori knowledge of statistical properties of successive speech periods, a shaped lattice structure is designed to cover the most probable points in the pitch space. The codebook index search starts with finding an open-loop estimate in the pitch space considering all dimensions and refining the open-loop estimate in a closed-loop search separately in each dimension based on the shaped lattice structure. The closed-loop search for the first subframe is for obtaining an absolute pitch period or a delta pitch while the closed-loop search for each of the other subframes is for obtaining a delta pitch for the respective subframe.

Abstract: A method of coding a sampled speech signal in which the speech signal is divided into sequential frames. For each current frame, a first set of linear prediction coding (LPC) coefficients are generated, where the number of LPC coefficients depends upon the characteristics of the current frame. If the number of LPC coefficients in the first set of the current frame differs from the number in the first set of the preceding frame, then a second expanded or contracted set of LPC coefficients is generated from the first set of LPC coefficients for the preceding frame. This second set contains the same number of LPC coefficients as are present in said first set of the current frame. Respective sets of line spectral frequency (LSP) coefficients are generated for the first set of LPC coefficients of the current frame and the second set of LPC coefficients of the preceding frame. The sets of LSP coefficients are then combined to provide an encoded residual signal.