Optimized trellis coded vector quantization of speech coder LSF parameters

Speech coders operating at low bit rates necessitate efficient encoding of the linear predictive coding (LPC) coefficients. Line spectral Frequencies (LSF) parameters are currently one of the most efficient choices of transmission parameters for the LPC coefficients. In this paper an optimized trellis coded vector quantization (TCVQ) scheme for encoding the LSF parameters is presented. When the selection of a proper distortion measure is the most important issue in the design and operation of the encoder an appropriate weighted distance measure has been used during the TCVQ construction process. We further applied the optimized TCVQ system for encoding the LSF parameters of the us Federal Standard (FS1016) 4.8 kbps speech coder. At lower bit rates, objective and subjective evaluation results show that the incorporated LSF TCVQ encoder performs better than the 34 bits/frame LSF scalar quantizer used originally in the FS1016 coder. The subjective tests reveal also that the 27 bit/frame scheme produces equivalent perceptual quality to that when the LSF parameters are unquantized.