A Low-Bit-Rate Extension Algorithm to the 8 kbit/s CS-ACELP Based on Adaptive Fixed Codebook Modeling

Hong Kook KIM  Hwang Soo LEE  

IEICE TRANSACTIONS on Information and Systems   Vol.E82-D   No.7   pp.1087-1092
Publication Date: 1999/07/25
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Speech Processing and Acoustics
speech coding,  code-excited linear prediction,  adaptive fixed codebook,  codebook search,  

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In this paper, we propose an adaptive encoding method of fixed codebook in CELP coders and implement an adaptive fixed code-excited linear prediction (AF-CELP) speech coder as a low-bit-rate extension to the 8 kbit/s CS-ACELP. The AF-CELP can be implemented at low bit rates as well as low complexity by exploiting the fact that the fixed codebook contribution to the speech signal is periodic, as is the adaptive codebook (or pitch filter) contribution. Listening tests show that the 6.4 kbit/s AF-CELP has a comparable quality to the 8 kbit/s CS-ACELP under real environmental test conditions.