ITU-T音频格式编解码代码，包括：G.711 G.721 G.723, 其中G723还支持16kbit/s 24kbit/s 40kbit/s几种码率。g72x.h g711.h是共用的头文件。-These are ITU-T speech codecs,include G.711 G.721 G.723,and G.723 also supports 16kbit/s 24kbit/s 40kbit/s. g72x.h and g711.h are common head files.