实现adpcm g726编码，有pcm音频源文件，有编码后的g726 wav文件用vlc直接可以播放。对研究g726的朋友应该会有参考价值。-adpcm g726 codec,give out an demo for g726 codec , form pcm file to g726 wav file , you can play it by vlc.

Define the preprocessor symbols to establish the vendor ID and device ID for the MFi PCM ADPCM extensions.