https://blog.faceutil.com/2017/03/31/%ec%98%a4%eb%94%94%ec%98%a4cd-mp3-%eb%b0%8f-flac-%ec%b6%94%ec%b6%9c-%eb%b3%80%ed%99%98-%ed%94%84%eb%a1%9c%ea%b7%b8%eb%9e%a8-cdex-%ed%8f%ac%ed%84%b0%eb%b8%94-%eb%b2%84%ec%a0%84-%e3%8e%80/