这段时间终于把手头的东西都搞完了，还剩下一个AEC这个模块，这个模块跟整个系统机制有很大关系，单独的模块意义不大。
另外，刚写完一个分类器，希望能大幅提升音乐流派分类的准确率。
下周正式开搞AEC，把之前做的一些事情记录一下。
https://en.wikipedia.org/wiki/Dynamic_range_compression
Downward compression reduces loud sounds over a certain threshold while quiet sounds remain unaffected. Upward compression increases the loudness of sounds below a threshold while leaving louder passages unchanged. Both downward and upward compression reduce the dynamic range of an audio signal.[2]
An expander performs the opposite function, increasing the dynamic range of the audio signal.[3] Expanders are generally used to make quiet sounds even quieter by reducing the level of an audio signal that falls below a set threshold level. A noise gate is a type of expander.[2]
原始音频：
放大二倍后的波形：
放大二倍后经过DRC(简单点说，大值小倍数变化，小值正常倍数变化，之前处理爆音时，本能的就使用过这个思想，没想到这玩意专业术语叫做DRC)处理，防止爆音后的波形。
原文：http://www.cnblogs.com/welen/p/4996265.html