Re: [Alsa-user] multichannel multiband FFT-based equalizer - README

[Sergei S. <ste...@li...>]

Fons,

regarding,

"
It means limited Q, but no discrete central frequencies.
"

- please implement in the given 8 points example a filter an equalizer,
changing 1.5 * Fs / 8, but not affecting other frequencies.


To be more versatile:

Case_1:

input signal is

sin(2 * PI * 1 * Fs / 8) + sin(2 * PI * 2 * Fs / 8)

Case_2:

sin(2 * PI * 1 * Fs / 8) + sin(2 * PI * 1.5 * Fs / 8) + sin(2 * PI * 2 * Fs / 8) .

I claim that if I select central frequencies as 

1 * Fs / 8
2 * Fs / 8

, them for changing gain of (1 * Fs / 8) will only change amplitude of
sin(2 * PI * 1 * Fs / 8), but not of sin(2 * PI * 2 * Fs / 8);

changing gain of o(2 * Fs / 8) will change amplitude of
sin(2 * PI * 2 * Fs / 8), but not of sin(2 * PI * 1 * Fs / 8);

in both cases of gain change in case of Case_2 amplitude of
sin(2 * PI * 1.5 * Fs / 8) will change.

Whatever implementation of yours should be limited to simple
FFT-based equalizer similar to the one I published. That is,
data from no more than two adjacent FFT buffers can be used.

Thanks in advance,
  Sergei.

On Tue, 3 Jan 2006 02:27:46 +0100
fons adriaensen <fon...@sk...> wrote:

> On Tue, Jan 03, 2006 at 03:12:50AM +0200, Sergei Steshenko wrote:
> 
> > In the case of DFT limited N means both limited Q and discrete
> > central frequencies in the terms of precise signal restoration.
> 
> It means limited Q, but no discrete central frequencies.
> BTW, I've used such 'interpolated frequency' filters many times
> in my professional work, and they are also in JAAA.
> 
> Bye for now !
> 
> -- 
> FA
> 
> 
> 
> 
> 
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