Patent ID: 7668713
Filing Date: 2010-02-23
Classification: G10L,H04W

Abstract:
1. A method for transcoding a bit stream encoded according to a mixed-excitation linear prediction (MELP) standard to a bit stream encoded according to a linear predictive coding (LPC) standard, comprising: decoding a bit stream into a first set of vocoder parameters compatible with the MELP standard; transforming the first set of vocoder parameters into a second set of vocoder parameters compatible with the LPC standard without converting the first set of vocoder parameters to an analog or digital waveform representation; and encoding the second set of vocoder parameters into a bit stream compatible with the LPC vocoder standard, wherein the transforming includes converting MELP spectrum parameters to LPC spectrum parameters, and wherein the converting of MELP spectrum parameters to LPC spectrum parameters includes: converting MELP line spectrum frequencies (LSF) to their equivalent normalized autocorrelation coefficients (R); and adding preemphasis effects to the normalized autocorrelation coefficients wherein the preemphasis addition is performed according to the following equation to form preemphasized autocorrelation coefficients R′(i):