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G.729.1是ITU-T近年来提出的一种嵌入式宽带变速率的语音编码标准.它可以根据信道的特征随时调整编码速率取得更好的宽带语音质量,这使得该编码算法具有很高的复杂度.在G.729.1标准中,固定码本搜索约占算法总复杂度的25%,为降低固定码本搜索算法的复杂度,提出一种分级并简化脉冲替换的方法.该算法依据似然估计向量大小对脉冲位置重新排序,利用两级搜索同时对第二级简化搜索来改善脉冲替换搜索的效率,从而减少搜索次数.实验结果表明,改进后的方法可使固定码书搜索次数降为G.729.1中全局脉冲替换方法的42.72%,并且保持了与其几乎相同的语音质量.
G.729.1 is a kind of embedded speech coding standard of broadband variable rate which proposed by ITU-T in recent years.It can adjust the coding rate according to the characteristics of the channel at any time to obtain better broadband speech quality, which makes the coding algorithm have high Complexity.In the G.729.1 standard, the fixed codebook search accounts for about 25% of the total complexity of the algorithm.In order to reduce the complexity of the fixed codebook search algorithm, a method of ranking and simplifying the pulse replacement is proposed, However, the size of the estimation vector reorder the pulse positions, and the two-level search simplifies the search of the second stage to improve the efficiency of the pulse replacement search, so as to reduce the search times. Experimental results show that the improved method can reduce the number of fixed codebook searches Is 42.72% of the global impulse replacement method in G.729.1, and maintains almost the same voice quality.