一种IPCAM的声学回声消除算法与实现

Algorithm & Implementation of Phonics Acoustic-Echo Cancellation for IP Camera

文章对IPCAM(IP Camera)网络摄像机在网络音频对讲过程中的各种回声干扰产生的原因进行了分析,对于其中的声学回声消除(AEC)算法进行了探讨,并在基于TMS320系列DSP芯片的IPCAM系统上,编程实现了一个全双工的声学回声消除器软件.这个实现是基于规格化最小均方差(NLMS)的算法,通过调整自适应FIR滤波器的可替换步长以调整方差收敛的速度,并在网络环境下进行实测,达到有效消除声学回声与延迟,均在可接受的范围内,即回声残余信号比远端信号低30 dB、对方声音信号延迟小于29ms.这一算法同样可以应用于VOIP网络电话、远程可视对讲系统等环境,根据需要在实际的网络环境下调整步长,以达到消除回声和缩短延迟的最优化效果.

The article discusses acoustic-echo cancellation technique in audio communication of IP Camera, and the algorithm and implementation of acoustic-echo cancellation （AEC）. The full-duplex software of acoustic-echo cancellation based on DSP chip of the TMS320 series is designed based on Normalized Least Mean Square （NLMS） algorithm. By changing the convergence speed of NLMS through the step length change of a Finite Impulse Response （FIR）, AEC could be reduced and delayed with signal of AEC 30 dB lower than remote voice feed and signal-delay of remote voice less than 29ms.This algorithm can be used for VOIP and remote visible-talkback system, and by adjusting the step length of FIR on network optimized effect of AEC and delay-reducing can be realized.