I take it you just want to strip off the videos soundtrack to play on your phone?
VLC will do it click here for instructions. I have just tried it and it took just over a minute for a 30 minute video. Only problem I had was that the file had an .mp4 extension so changed it to .mp3 and it worked fine but have not tried porting it to an android or apple phone. You may have problems if the .mp4 is DRM protected.