How to test Audio Line in to Line out (Ubuntu)

預設 Ubuntu 把 Line in to Line out loopbak 關掉, 必須下指令把他開啟

#manualy start the module-loopback
pactl load-module module-loopback

#configure your system to load module-loopback on startup
#this places load-module module-loopback at the end of
#the /etc/pulse/default.pa pulseaudio configuration file.
sudo sh -c ' echo "load-module module-loopback" >>  /etc/pulse/default.pa '

參考: get-the-audio-from-line-in-to-output-to-the-speaker