Design of a Robust LSP Quantizer for a High-Quality 4-kbit/s CELP Speech Coder

Yusuke HIWASAKI  Kazunori MANO  Kazutoshi YASUNAGA  Toshiyuki MORII  Hiroyuki EHARA  Takao KANEKO  

IEICE TRANSACTIONS on Information and Systems   Vol.E87-D   No.6   pp.1496-1506
Publication Date: 2004/06/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Speech and Hearing
speech coding,  spectral quantization,  line spectrum pairs,  line spectral frequencies,  split vector quantization,  

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This paper presents an efficient LSP quantizer implementation for low bit-rate coders. The major feature of the quantizer is that it uses a truncated cepstral distance criterion for the code selection procedure. This approach has generally been considered too computationally costly. We utilized the quantizer with a moving-average predictor, two-stage-split vector quantizer and delayed decision. We have investigated the optimal parameter settings in this case and incorporated the quantizer thus obtained into an ITU-T 4-kbit/s speech coding candidate algorithm with a bit budget of 21 bits. The objective performance is better than that with a conventional weighted mean-square criterion, while the complexity is still kept to a reasonable level. The paper also describes the codebook design and techniques that were employed to achieve robustness in noisy channel conditions.