【作者】 高浩；

【导师】 须文波；

【作者基本信息】 江南大学 ， 计算机应用技术， 2006， 硕士

【摘要】 在现代各种通信系统中,语音编码一直是一项重要的、必不可少的业务。本文综述了语音编码发展的现状,全面系统地分析、介绍了改进的多带激励语音编码的原理,重点研究了多带激励低速率语音编码的实现方法。在多带激励低速率语音编码研究中,本文依据动态规划技术原理,提出了一种有效而实用的前后各看一帧的双向基音跟踪平滑算法。最后得到的实验结果表明,采用该方法对基音周期进行跟踪平滑处理,可去除语音帧之间基音周期的“跳跃”点,保证基音周期轨迹的正确性,显著提高基音周期估计的准确度。同时设计了两级离散余弦变换的编码方案,采用该方案对逐帧变化的谱幅度参数进行自适应动态量化编码,大大减少了编码比特数,实现了2.4kb/s及其以下速率的多带激励语音编码器。最后,设计了完整的2.4kb/s多带激励语音压缩编码方案。在多带激励低速率语音编码实现过程中,我们首先建立了语音编码硬件基础,即基于TI公司的TMS320VC54XX系列DSP平台,对此做了比较详细的介绍。然后,提出了在TMS320VC5402上实现该语音算法的一个解决方案,并讨论了该方案实现过程中所遇到的一些问题以及解决办法。最后,通过对程序进行测试验证,编解码结果正确,笔者给出了实验结果以及就如何进一步降低编解码算法的速率以及复杂度等问题作了一些探索。更多还原

【Abstract】 Speech coding is an important and indispensable service in different modern communication systems.The current situation of speech coding is summarized in this paper. The principles of the improved mufti-band excitation(MBE) speech code are analyzed and introduced in detail with emphasis on the implement method of MBE speech coding at low bit rate.In the study of MBE speech coding, a new efficient practical look-back and look-ahead pitch tracking smoothing algorithm is presented based on the dynamic programming approach. The experimental results show that it can remove the "jumper" of pitch between the frames, guarantee the exactness of pitch track and improve the accuracy of pitch estimation.The two stage discrete cosine transformation coding scheme is designed.Using this scheme spectral magnitude parameters changing frame-by-frame are quantized adaptively and the coded bit rate of speech is largely reduced. A scheme of 2.4/kb/s MBE speech coder is designed completely.During the concretely realize of the MBE speech coding, we set up the hardware elements of the speech coding, which is the TMS320VC54xx DSP platform of TI Inc. We explicitly introduce it in this paper too. In the following we bring out a blue print of implementation based on the TMS320VC5402.Finally we even introduce the problems we met and the solutions we found.At last, by testing the procedure, the coding and decoding results are all correct.Then the author give the results of this experiment and some innovative improvement thoughts on further reducing the code-rate and decreasing the complexity of vocoders are included in this dissertation.更多还原