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Open AccessArticle

A Search Complexity Improvement of Vector Quantization to Immittance Spectral Frequency Coefficients in AMR-WB Speech Codec

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Department of Electrical Engineering, National Taipei University of Technology, 1, Sec. 3, Chung-hsiao E. Rd., Taipei 10608, Taiwan
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Department of Electrical Engineering, National Chin-Yi University of Technology, 57, Sec. 2, Zhongshan Rd., Taiping Dist., Taichung 41170, Taiwan
*
Author to whom correspondence should be addressed.
Academic Editor: Ka Lok Man
Symmetry 2016, 8(10), 104; https://doi.org/10.3390/sym8100104
Received: 21 June 2016 / Revised: 29 August 2016 / Accepted: 27 September 2016 / Published: 30 September 2016
(This article belongs to the Special Issue Symmetry in Systems Design and Analysis)
An adaptive multi-rate wideband (AMR-WB) code is a speech codec developed on the basis of an algebraic code-excited linear-prediction (ACELP) coding technique, and has a double advantage of low bit rates and high speech quality. This coding technique is widely used in modern mobile communication systems for a high speech quality in handheld devices. However, a major disadvantage is that a vector quantization (VQ) of immittance spectral frequency (ISF) coefficients occupies a significant computational load in the AMR-WB encoder. Hence, this paper presents a triangular inequality elimination (TIE) algorithm combined with a dynamic mechanism and an intersection mechanism, abbreviated as the DI-TIE algorithm, to remarkably improve the complexity of ISF coefficient quantization in the AMR-WB speech codec. Both mechanisms are designed in a way that recursively enhances the performance of the TIE algorithm. At the end of this work, this proposal is experimentally validated as a superior search algorithm relative to a conventional TIE, a multiple TIE (MTIE), and an equal-average equal-variance equal-norm nearest neighbor search (EEENNS) approach. With a full search algorithm as a benchmark for search load comparison, this work provides a search load reduction above 77%, a figure far beyond 36% in the TIE, 49% in the MTIE, and 68% in the EEENNS approach. View Full-Text
Keywords: speech codec; vector quantization (VQ); triangular inequality elimination (TIE); immittance spectral frequency (ISF); VoIP speech codec; vector quantization (VQ); triangular inequality elimination (TIE); immittance spectral frequency (ISF); VoIP
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Yao, B.-J.; Yeh, C.-Y.; Hwang, S.-H. A Search Complexity Improvement of Vector Quantization to Immittance Spectral Frequency Coefficients in AMR-WB Speech Codec. Symmetry 2016, 8, 104.

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