針對代數碼激式線性預測編碼器(ACELP)，本論文共完成兩個主要研究項目分別為高效率的轉碼與編碼。首先，在行動通訊與網際網路的通訊上，我們提出半速率GSM與G.729語音編碼器之間的轉碼架構。其次對ACELP脈衝搜尋程序提出快速隨機碼簿搜尋演算法。
語音編碼器的轉碼方法藉由半速率GSM與G.729編碼參數的轉換被提出，通訊於無線通訊與網際網路。與傳統的解碼然後編碼(DTE)方法做比較，所提出的參數轉換方法，可以以較低的計算複雜度及編碼延遲，提供不同語音編碼器溝通。模擬結果顯示所提出的方法，可以降低約30%左右的計算量，在聽覺上聽不出語音品質的降低。
降低ACELP的計算複雜度，以聲音脈衝響應的簡化相關性矩陣為基礎，我們提出高效率碼簿搜尋技巧。更進一步提出簡化相關性矩陣和脈衝位置預選結合方法，此方法不僅在事先計算自相關矩陣時可以降低算術計算量，還可以降低脈衝位置組合的數量。實驗結果證明所提出的方法，可以有效的降低在ACELP碼簿搜尋程序中的計算量，而不降低聽覺上的語音品質。

The two major research topics for algebraic code excited linear predictive (ACELP) of this dissertation are efficient translation and coding methods. First, we proposed the architecture of transcoding between global system for mobile communications (GSM) half rate and G.729 Speech Coders across Mobile and IP Networks. Second, the fast stochastic codebook search algorithms for reduction of the algebraic code excited linear predictive (ACELP) are proposed.
The speech coding translation scheme by transferring coding parameters between GSM half rate and G.729 coders is proposed over wireless and network. Compared to the conventional decode-then-encode (DTE) scheme, the proposed parameter conversions provide speech interoperability with reducing computational complexity and coding delay. Simulation results show that the proposed methods can reduce about 30% computational load achieve almost imperceptible degradation in performance.
To reduce the computational complexity of Algebraic Code-Excited Linear Prediction (ACELP) coders, we propose an efficient codebook search mechanism based on a simplified correlation matrix of the vocal impulse response. Furthermore, proposed Joint scheme by combining the simplified correlation matrix method and a pulse position prediction scheme, it not only decreases arithmetic complexity in pre-computing autocorrelation matrix but also reduce the number of pulse position combinations. The simulation and experimental results show that the proposed method provides an effective reduction in the computational load of the ACELP codebook search procedure with no discernible degradation of the speech quality.

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