参考链接:http://veryitman.com/2018/02/14/%E9%9F%B3%E8%A7%86%E9%A2%91%E7%BC%96%E7%A8%8B-%E7%BC%96%E8%AF%91-faac-faad2/ github源码:https://github.com/veryitman/faacfaad2/tree/master