How to use vDSP in iOS for converting sound file to FFT

Question

I am new to Audio framework but after searching a while i found Accelerate framework provided by iOS api for Digital Signal Processing. In my project i want to convert a sound file to fft so that i can compare two sounds using fft. So how should i proceed with this? I have gone through apples aurio touch sample app but they didnt use accelerate framework. Can any body help me to convert a sound file to fft and then compare using correlation .

Answer 1

The FFT is a complex beast, not something that can be comprehensively discussed in a single text box (I know accomplished engineers who have taken multiple semesters of classes studying topics that boil down to Fourier Transform analysis). Because of the nature of Accelerate framework's tasks, it too is a non-trivial discussion topic.

I would suggest reading Mike Ash's Friday Q&A on FFTs, where he covers some basic use of the vDSP functions to get FFT values, as a starting place.

See this DSP Stack Exchange answer for discussion on convolution and cross-correlation.