https://free-audio-cd-to-mp3-converter.kr.uptodown.com/windows
http://mp3gain.sourceforge.net/download.php
http://blog.naver.com/PostView.nhn?blogId=mascn_black&logNo=130133279242 http://blog.naver.com/PostView.nhn?blogId=mascn_black&logNo=130133328262