Interpolation in a speech decoder of a transmission system on the basis of transformed received prediction parameters

摘要

A transmission system wherein a speech signal is represented by a plurality of prediction parameters updated once per frame. Each frame comprises a plurality of sub-frames in which an excitation signal generated by a fixed codebook and an adaptive codebook is updated. In order to enhance the reconstructed speech quality the prediction coefficients are interpolated at the decoder by an LPC coefficient interpolator to obtain interpolated prediction coefficients for each sub-frame. According to the present invention the interpolation of the prediction coefficients is not based on the prediction coefficients used for transmission, such as reflection coefficients or Log Area Ratios, but on Line Spectral Frequencies. This reduces degradation of speech quality due to interpolation.