I believe flaskmpeg has an (dvd) audio to mp3 option...not sure though.
If its ordinary dts or ac3 audio id first rip the dvd.
Then demux the audio with fex. pgcdemux.
Then use ac3towav or HeadAC3he(if its ac3) and convert the wavs to mp3 with whatever audio encoder suits you.
Or use dbpoweramp with the directshow codec (both ac3 and dts)
