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Efficient search and design procedures for robust multi-stage VQ of LPC parameters for 4 kb/s speech coding

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4 Author(s)
LeBlanc, W.P. ; Dept. of Syst. & Comput. Eng., Carleton Univ., Ottawa, Ont., Canada ; Bhattacharya, B. ; Mahmoud, S.A. ; Cuperman, V.

A tree-searched multistage vector quantization (VQ) scheme for linear prediction coding (LPC) parameters which achieves spectral distortion lower than 1 dB with low complexity and good robustness using rates as low as 22 b/frame is presented. The M-L search is used, and it is shown that it achieves performance close to that of the optimal search for a relatively small M. A joint codebook design strategy for multistage VQ which improves convergence speed and the VQ performance measures is presented. The best performance/complexity tradeoffs are obtained with relatively small size codebooks cascaded in a 3-6 stage configuration. It is shown experimentally that as the number of stages is increased above the optimal performance/complexity tradeoff, the quantizer robustness and outlier performance can be improved at the expense of a slight increase in rate. Results for log area ratio (LAR) and line spectral pairs (LSPs) parameters are presented. A training technique that reduces outliers at the expense of a slight average performance degradation is introduced. The method significantly outperforms the split codebook approach

Published in:

Speech and Audio Processing, IEEE Transactions on  (Volume:1 ,  Issue: 4 )