A Hybrid Speech Coder Based on CELP and Sinusoidal Coding

摘要

In this paper, we study a new hybrid speech coder which employs a modified version of the harmonic sinu- soidal analysis to encode the periodic contents of speech wave- form and to split the speech spectrum into two frequency regions of harmonic and random components. A reliable fundamental frequency is estimated for the harmonic region using both speech and its linear predictive (LP) residual spectrum. The peak enve- lope of speech spectrum is encoded in terms of the coefficients of an all-pole spectrum. A harmonic tracking algorithm appropri- ately interpolates the sinusoidal parameters to achieve a smooth transition between the parameter update points and to recon- struct an essential level of periodicity in the synthetic voiced speech. The random part of spectrum and unvoiced speech are coded using the conventional CELP algorithm. The individual components are then combined at the decoder to obtain the syn- thetic speech. The proposed hybrid coder which combines the powerful features of the sinusoidal and CELP coding algorithms yeilds a high quality synthetic speech at 4.05 kbps.