IP电话系统中的消回声处理

分析了IP电话系统中回声的特点，并针对其回声具有路径延尺、延尺抖动大等特点，提出了一种基于延尺分析的自适应回声消除器设计的新思想和相关算法。介绍了自适应回声消除器的基本结构及各个功能模块，例如：变阶自适应滤波器，语音状态检测器，延尺分析器和NLMS算法控制器。本文还详细论述了以TMS320C6201DSP为硬件平台实现能运用在IP电话网关中的自适应回声消除器及其在IP电话系统中的连接关系。在文章的最后，列举了自适应回声消除器的性能测试结果，并分析了自适应回声消除器的优点，证明了自适应回声消除器能很好地解决IP电话系统中的回声消除问题。

Echo Cancellation in IP Telephone System

The characteristics of the echoes in the IP telephone system are analyzed. According to these echo characteristics such as very long echo path, great delay of echo jitter, etc. a new idea of design an "adaptive echo canceller (AEC)"and its associated algorithms are proposed. The structure of AEC as well as its composing modules, are introduced such as the speech detector, the adaptive filter,the time-delay estimator and the NLMS algorithm controller. We have also discussed how to implement the adaptive echo canceller on TMS320C6201 DSP which can be used in the IP telephony gateway, and how to link it with the IP telephony system. Finally, the performances of test results of the adaptive echo canceller are summarized, and its main advantages are analyzed. It is proved that the adaptive echo canceller can effectively cancel the echoes in the IP telephony system.