As applied to a vector quantization (VQ) codebook search, a combined version of a dynamic triangular inequality elimination (DTIE) and a tree-structured VQ (TSVQ) algorithm, designated as the DTIE-TSVQ approach, is presented in this letter as an efficient way to reach the aim of search performance improvement by successive updating of the search scope and reduced search load through the DTIE algorithm. In this manner, this proposal features the combined advantages of a TIE and a TSVQ algorithm such that 100% search accuracy is rendered together with a remarkable reduction in computational load. At the end of this work, this proposal is validated as a superior algorithm over TIE and conventional TSVQ algorithms by a high computational load saving up to 97.45% when dealing with line spectral frequency (LSF) quantization in a G.729 speech codec and image VQ encodings.

This study proposes an improvement to tree-structured vector quantization (TSVQ). The selected codeword of TSVQ is employed as the reference codeword. The dynamic triangular inequality elimination (DTIE) is employed to improve the performance of TSVQ. In the DTIE-TSVQ approach, the selected codeword and SNR are identical to that of full-search vector quantization (FSVQ), and the computational saving is better than that of TIE-VQ. The experimental results confirm that DTIE-TSVQ outperforms TIE-VQ, TSVQ.

This work aims to present a combined version of reduced candidate mechanism (RCM) and iterationfree pulse replacement (IFPR) as a novel and efficient way to enhance the performance of algebraic codebook search in an algebraic code-excited linear-prediction (ACELP) speech coder. As the first step, individual pulse contribution in each track is given by RCM, and the number N of candidate pulses is then specified. Subsequently, the replacement of a pulse is performed through the search over the sorted top N pulses by IFPR, and those of 2 to 4 pulses are carried out by a standard IFPR. Implemented on a G.729A speech codec, this proposal requires as few as 24 searches, a search load tantamount to 7.5% of G.729A, 37.5% of the global pulse replacement method (iteration=2), 50% of IFPR, but still provides a comparable speech quality in any case. The aim of significant search performance improvement is hence achieved in this work..