Converting an FFT to a spectogram

Question

I have an audio file and I am iterating through the file and taking 512 samples at each step and then passing them through an FFT.

I have the data out as a block 514

Answer 1

Just so people know I've done a LOT of work on this whole problem. The main thing I've discovered is that the FFT requires normalisation after doing it.

To do this you average all the values of your window vector together to get a value somewhat less than 1 (or 1 if you are using a rectangular window). You then divide that number by the number of frequency bins you have post the FFT transform.

Finally you divide the actual number returned by the FFT by the normalisation number. Your amplitude values should now be in the -Inf to 1 range. Log, etc, as you please. You will still be working with a known range.