Improved spectral tracking using interpolated linear prediction parameters

Conventional interpolation of Linear Prediction (LP) parameters can provide a poor spectral match to the underlying speech signal for the intermediate subframes. In this paper, we present a method of modifying the interpolation endpoint LP parameters to improve the spectral tracking over all subframes. This ‘warping’ algorithm is based on minimizing the distortion between the interpolated LP parameters and those computed directly from the speech signal. The algorithm has been integrated into the Adaptive Multi Rate (AMR) speech codec. Our results show that this method enhances coder performance by smoothing out the LP parameter tracks and reducing coding distortion.