Abstract: In order to recover the excitation energy quickly and keep the adaptive excitation contribution percentage in the entire excitation after bit-stream packet loss, the two excitation gains (Gp 305 and Gc 306) can be first transformed into the two other special parameters: one is the entire excitation energy and another is the energy ratio of the adaptive excitation contribution portion relative to the entire excitation energy. Then, the transformed parameters are quantized and sent to decoder. At the decoder side, the quantized parameters are transformed back to the original form of the gains (Gp 305 and Gc 306).

Abstract: A method of significantly reducing error propagation due to voice packet loss, while still greatly profiting from long-term pitch prediction, is achieved by adaptively limiting the maximum value of the pitch gain for the first pitch cycle within one frame. A speech coding system for encoding a speech signal, wherein said a plurality of speech frames are classified into said a plurality of classes depending on if the first pitch cycle is included in one subframe or several subframes. The pitch gain is set to a value significantly smaller than 1 for the subframes covering first pitch cycle; wherein the pitch gain reduction is compensated by increasing the coded excitation codebook size or adding one more stage of excitation for the subframes covering the first pitch cycle.