An improved 2.4 kbps class-dependent CELP speech coder
Yingbo Jiang, V. Cuperman · 2002
This paper presents an improved 2.4 kbps class-dependent CELP speech coder. The improved coder is based on our previous efforts on a 2.4 kbps CELP coder. New classification schemes in both open-loop and closed-loop are used. An extra transition class is used in the closed-loop classification. We developed a predictive LSP VQ to reduce LPC bit rate to as low as 18 bits/frame (30 ms) while maintaining low spectral distortion. Experimental results show that the quality of synthesized speech is improved. We also discuss the results obtained from class-dependent weighting filters, and a class-dependent postfilter.