Real-time implementation and performance of a 16 kb/s low-delay CELP speech coder

Author

Chen, Juin-Hwey ; Melchner, Melvin J. ; Cox, Richard V. ; Bowker, Duane O.

Author_Institution

AT&T Bell Lab., Murray Hill, NJ, USA

fYear

1990

fDate

3-6 Apr 1990

Firstpage

181

Abstract

A real-time implementation of the low-delay code-excited linear prediction (LD-CELP) speech coder based on the AT&T DSP32C is described. The performance of the coder is described. Recursive windowing is used to calculate the autocorrelation coefficients by dividing the Levinson-Durbin recursion into smaller parts and spreading the computation over several speech vectors. The LD-CELP encoder uses about 90% of the processor time of an 80-ns DSP32C, while the decoder uses about 40%. Hence, the coder is implemented on two DSP32Cs. For a single encoding with clear or noisy channels, the speech quality produced by this coder is either equivalent to or better than the CCITT G.721 standard 32-kb/s ADPCM. However, for multiple asynchronous encodings the ADPCM coders gives slightly better performance. The LD-CELP coder passes dual-tone multifrequency tones and 300-, 1200-, and 2400-b/s modem signals

Keywords

computerised signal processing; decoding; encoding; real-time systems; speech analysis and processing; telecommunications computing; vocoders; 16 kbit/s; 80 ns; CELP speech coder; DSP32C; Levinson-Durbin recursion; autocorrelation coefficients; code-excited linear prediction; decoder; dual-tone multifrequency tones; encoder; low-delay; modem signals; real-time implementation; Autocorrelation; Code standards; Decoding; Delay; Linear predictive coding; Modems; Signal processing algorithms; Speech; Speech analysis; Speech coding; Speech synthesis; Testing; Vectors;

fLanguage

English

Publisher

ieee

Conference_Titel

Acoustics, Speech, and Signal Processing, 1990. ICASSP-90., 1990 International Conference on

Conference_Location

Albuquerque, NM

ISSN

1520-6149

Type

conf

DOI

10.1109/ICASSP.1990.115568

Filename

115568