4 kb/s improved CELP coder with efficient vector quantization

Author

Ozawa, Kazunori ; Miyano, Toshiki

Author_Institution

NEC Corp., Kanagawa, Japan

fYear

1991

fDate

14-17 Apr 1991

Firstpage

213

Abstract

A 4 kb/s LCELP (learned code excited linear prediction) speech coding method is presented. In order to improve conventional CELP speech quality at around 4 kb/s, in LCELP, a learned codebook designed by the LBG method is used to efficiently represent an excitation signal. An effective orthogonalization method is developed. Delayed-decision search is adopted to search for a globally optimal code-vector combination over a frame. In order to allocate more bits to the excitation codebook, filter LSP parameters are efficiently quantized by using a multistage vector quantizer with multiple candidates. Experimental results show that 4 kb/s LCELP achieves an average of 10.8 dB segmental signal-to-noise ratio, which is 0.6 dB higher than that for 4.8 kb/s conventional CELP

Keywords

encoding; filtering and prediction theory; speech analysis and processing; vocoders; 4 kbit/s; CELP coder; LBG method; LCELP; delayed-decision search; effective orthogonalization method; excitation signal; filter LSP parameters; globally optimal code-vector combination; learned code excited linear prediction; learned codebook; segmental signal-to-noise ratio; speech coding; vector quantization; Bit rate; Decoding; Delay; Filters; Land mobile radio; Linear predictive coding; Search methods; Speech codecs; Speech coding; Vector quantization;

fLanguage

English

Publisher

ieee

Conference_Titel

Acoustics, Speech, and Signal Processing, 1991. ICASSP-91., 1991 International Conference on

Conference_Location

Toronto, Ont.

ISSN

1520-6149

Print_ISBN

0-7803-0003-3

Type

conf

DOI

10.1109/ICASSP.1991.150315

Filename

150315