[LAD] FFT 1D real

[Alfs Kurmis]

 Citējot *Fons Adriaensen <fons at linuxaudio.org> [1]*:
>    > How from ...1024 or 2048 or 4096... FFT return values i
> calculate
>    > power magnitudes for all bands,
>    > and finally values for visual 10-20 hopping bars, like in
> Winamp ,
>    > XMMS , QMMP ... ?
> 
>    If you want such a display the FFT is not a good way to do it.
>    It's possible but not simple if you want a correct result.
  What is good/best way to calculate values for visual 10-20 hopping
 bars like in GUI audio players ?
>    > 43303.2715 + 796.7285 = 44100 or 44100 - 43303.2715 =
> 796.7285>
>    > Why Frequency 796.7285 is mirrored as Frequency 43303.2715 ,
> and magnitude for both Frequencies is divided by 2 ????
> 
>    Because you are using a complex FFT, and the imaginary part
>    of your signal is zero. That means that the spectrum must be
>    symmetric.
> 
>    > Is here way direct calculate full magnitude and without
> Frequency
>    > mirroring , in band 0 Hz ... FSampl/2 ONLY ,
> 
>    Use an FFT operating on real data instead of complex.
  Can U gimme pointers to such functions ?
 What about all Radix algorithms ?
  Tnx in advance
  Alf
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Links:
------
[1] mailto:fons at linuxaudio.org
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