mp4tomp3

for f in $(ls -1 *.mp4); do ff=$(echo $f | sed -e 's/「/_/g' -e 's/」//g');mv $f $ff; done
for f in $(ls -1 *.mp4);do ffmpeg -i "${f}" -codec:a libmp3lame -qscale:a 4 -id3v2_version 3 -metadata artist="artist name" "${f%.mp4}".mp3;done