An adaptive multi-rate wideband (AMR-WB) code is a speech codec developed on the\nbasis of an algebraic code-excited linear-prediction (ACELP) coding technique, and has a double\nadvantage of low bit rates and high speech quality. This coding technique is widely used in modern\nmobile communication systems for a high speech quality in handheld devices. However, a major\ndisadvantage is that a vector quantization (VQ) of immittance spectral frequency (ISF) coefficients\noccupies a significant computational load in the AMR-WB encoder. Hence, this paper presents a\ntriangular inequality elimination (TIE) algorithm combined with a dynamic mechanism and an\nintersection mechanism, abbreviated as the DI-TIE algorithm, to remarkably improve the complexity\nof ISF coefficient quantization in the AMR-WB speech codec. Both mechanisms are designed in a\nway that recursively enhances the performance of the TIE algorithm. At the end of this work, this\nproposal is experimentally validated as a superior search algorithm relative to a conventional TIE,\na multiple TIE (MTIE), and an equal-average equal-variance equal-norm nearest neighbor search\n(EEENNS) approach. With a full search algorithm as a benchmark for search load comparison, this\nwork provides a search load reduction above 77%, a figure far beyond 36% in the TIE, 49% in the\nMTIE, and 68% in the EEENNS approach.
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