title: How to generate the audio spectrum using fft in C++?
body: <p>I want to generate an audio spectrum (as seen in <a href="http://www.youtube.com/watch?v=ZNT8Sn4IKbo" rel="noreferrer">this video</a>) of a mp3 audio file. Basically this problem requires calculating the fft of the audio signal. How do I program this in C/C++? </p>
  
  <p>I've looked at a couple of open source libraries such as <a href="http://www.fftw.org/" rel="noreferrer">FFTW</a> and I really don't know how to use these for my problem. Any help would be greatly appreciated. Thanks in advance!</p>