[FFmpeg-devel] [OPW] OPW Project Proposal

Michael Niedermayer michael at niedermayer.cc
Sat Nov 5 15:32:16 EET 2016

On Fri, Nov 04, 2016 at 11:37:24PM +0530, Pallavi Kumari wrote:
> >> ok, do you know how to compute that or should i explain it ?
> Explanation will help. Is there any function in FFmpeg to get absolute
> value of FFT?

hypot() of the 2 real components of each complex value should work

complex numbers are like dots on a paper, if you declare the middle
of the paper as 0, the 2 components are the x and y coordinates of
a complex number and the distance to the 0 point is the absolute

> and how to get frequency data?

the data[i] array  after the FFT is so that data[i] are the values
for the frequency i. You may need to permute them though

see libavcodec/tests/fft.c for how exactly the fft relates to a
reference fft

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Does the universe only have a finite lifespan? No, its going to go on
forever, its just that you wont like living in it. -- Hiranya Peiri
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