Evaluation of Potential Efficiency of Speech Coding Using Different Parameters of Linear Prediction

Abstract

The paper presents the results for estimating the potential coding efficiency of spectrum envelope waveform (SEW) of speech signals (SS) by using the linear prediction (LP) method and using different sets of alternative equivalent parameters (AEP) that include line spectral pairs/projections (LSP), line spectral frequencies (LSF), and alternative line spectral parameters of highest splitting (LSP-HS and LSF-HS). These results are derived by the proposed approach based on using the LP method for SS SEW coding with maximum frame overlap during its analysis. It includes the examination of such coding scheme as approaching an appropriate analog vector source in each of AEP spaces, the stepwise designing of an appropriate vector codebook in each of spaces with gradual increase of its size and employing the ideal scheme of vector quantization with exhaustive search at each stage. The distortions versus rate relationships have been calculated based on the results of analysis in each of AEP spaces. In addition, a generalized function is proposed for approximation of the specified relationships. The technique is presented that makes it possible in each AEP space to estimate Shannon’s lower bound, the dispersion of the Gaussian equivalent source, differential entropy, redundancy, values of the weighting constant in the generalized formula of entropy, and other entropy characteristics of coding the equivalent sources (parameters of SS SEW) in these spaces. The efficiency indicators of real and potential coding of corresponding AEP are proposed and calculated. It has been shown that in conjunction with the combination of proposed efficiency indicators, the best results demonstrate spaces of line spectral parameters of highest splitting (LSP-HS and LSF-HS).