title: Android : convert an audio file into array of complex numbers (for FFT)
body: <p>In order to process a FFT on an audio signal, I first need to <strong>convert my audio file into an array of complex numbers</strong>. I still don't understand if this part requires to save a .CSV of .TXT file on my sd card or if I can simply stock data in my application as a variable.
  I would simply like to understand how this part really works in order to go further in my FFT program : <strong>from my .3gpp audio file</strong> (by the way, is it a good format to use for what I am doing?) saved on my sd card, what should I do to have my array of complex numbers, the input for the FFT ?</p>
  
  <p>If anyone has an example of existing code used to convert audio file to binary data, I would really appreciate to take a look at it and to understand how to implement it in my activity. </p>