[Audio] echo cancellation

被歧視了 QQ
http://wiki.seeedstudio.com/ReSpeaker_2_Mics_Pi_HAT/
https://github.com/respeaker/mic_hat
https://github.com/voice-engine/voice-engine
https://github.com/Kitt-AI/snowboy

還沒解決，但參考這幾篇想想看
https://tinkerboarding.co.uk/wiki/index.php/Google-Assistant-SDK
http://lac.linuxaudio.org/2013/download/slides.pdf
https://gist.github.com/aflaxman/6300595

=>  https://github.com/respeaker/respeaker_for_raspberrypi

順便看一下 alsa 的 config 意義
http://www.sabi.co.uk/Cfg/ALSA/asound_simple.conf

ReSpeaker 的設定參考
https://github.com/wzpan/dingdang-robot/wiki/respeaker-2-mics-pi-hat