METHOD OF AND MEANS FOR VARIABLE-RATE CODING OF LPC PARAMETERS

A signal exhibiting redundancy, such as speech subjected to linear predictive coding, is transmitted in a reduced bandwidth by performing a linear interpolation over a number of frames. Interpolated coefficients are tested against quantized values to see if they differ by no more than a threshold. If they do not, only the last frame is sent and intermediate values are reconstructed by interpolation. If the interpolated values differ by more than the threshold from the quantized values, the number of frames for interpolation is reduced and the interpolation is repeated. This is continued until either interpolation is successful or else the next consecutive frame is sent. The required bandwidth for transmission can be varied by varying the threshold, the maximum number of frames for interpolation, the number of LPC coefficients, or a combination of these.