【作者】 邹绘华；

【导师】 李双田； 孙怡；

【作者基本信息】 大连理工大学 ， 通信与信息系统， 2002， 硕士

【摘要】 语音编码技术在数字通信系统中起着重要的作用。在传输比特率限制十分严格的场合下，超低速率语音编码则具有特别重要的意义。 作为低速率编码一种重要算法，美国联邦标准MELP算法在2.4Kb／s的速率下取得了不错的语音质量，但是仍然存在不少的问题，尤其是在非平稳语音段和编码效率方面。 本文对混合激励(MELP)算法进行了深入研究，针对编码效率不高的问题，提出了匀速率帧间插值算法；在G.729B的VAD算法基础上提出了BD-VAD算法；本文调查研究了变速率语音编码的各种算法，并研究了本语音分析系统中语音信号各参数的帧间相关性之后，进一步压缩速率，提出了基于频谱斜率约束条件的帧间插值算法，其语音质量、运算复杂度与原算法接近。 以此方案建立的语音编码／解码系统传输速率降到了300～800b／s。经重建语音信号比较及主观试听表明，该系统性能与美国联邦标准推荐的2.4kb／s混合激励线性预测(MELP)算法较接近或下降有限。更多还原

【Abstract】 Speech Coding is of great importance in digital communication systems. At the situation where the transmission rate is limited strictly, Very Low Bit Rate Speech Coding (LBRSC) is especially significant.As an important algorithm of LBRSC, the Mixed Excitation Linear Prediction (MELP) algorithm which was choosen as U.S. Federal Standard has got quite good speech quality at the rate of 2.4Kb/s, but there are still some perceivable problems, particularly around non-stationary speech segments and in the aspect of coding efficiency.In this thesis, MELP algorithm is deeply studied. In order to higher the coding efficiency, the interpolation algorithm of invariable frame rate is presented; Based on the VAD algorithm in G.729B, the BD-VAD algorithm is promoted; After the investigation and analysis of the inter-frame parameter correlation, an interpolation algorithm based on the spectral slope constraint is presented to lower the coding rate, meanwhile, the speech quality and the operating complexity is similar to MELP algorithm.The transmission bit rate of this speech coding/decoding system is lowered to 300-800 bps. After comparing and subjectively evaluating the reconstructed speech, it is concluded that the performance of this system approaches to that of 2.4Kb/s MELP algorithm which is in the Federal Telecommunication Recommendation.更多还原