Audio equalizer using FFmpeg

Question

I'm developing audio player using FFmpeg. I want to add audio equaliqer to my app, but I don't know how to do it. I know that FFmpeg has a FFT functions, but I have count of samples that not mutch with any power of 2. I also tried to use other FFT libraries, but I have some noise on my audio after equalization. Can anybody help me to understand how to use FFmpeg's FFT functions or any oter ways to implement audio-eq using FFmpeg?

Answer 1

If you want do use an FFT for fast convolution filtering, don't use the mp3 sample count. Instead, you will need to re-buffer the audio data (perhaps using a circular buffer) to get new buffers of the appropriate size needed for the FFT. You will also need to zero-pad the FFT in order to do overlap-add or overlap-save fast convolution FFT filtering. You will need to compute the length of the impulse response of your desired equalization in order to zero-pad the FFT by the appropriate amount. This may involve modification of the equalization filter in order to get a reasonable (finite) length FFT.