ffmpeg is a light weight and fastest encoder and decoder too. usually used for converting the video formats for compatibility issues with mobile devices. I have been using this method ever since i figured out that some add-on’s of the mozilla firefox offer you to convert the video songs from youtube into mp3.
ffmpeg -i input.mp4 output.mp3
this will do the work for us in linux.
interestingly ffmpeg is also available for other operating system’s like mac and windows as it is developed under python.