audio mixer

https://blog.csdn.net/jeffasd/article/details/77155187

https://blog.csdn.net/jeffasd/article/details/77335874?utm_source=blogxgwz2（视频会议中混音后溢出问题的研究及解决方法）

https://wenku.baidu.com/view/884624d97f1922791688e85b.html（多媒体会议中新型快速实时混音算法）

http://www.cppblog.com/jinq0123/archive/2007/10/31/audiomixingstudy.html