FFT Filter What does it do

[Martin E]

So what does a FFT Filter actually do? Is this useful for mastering? I tried out the filter in audacity on a song. I cut the low end and it cleaned it up very nicely. Is there any other software doing this and maybe even in a better way?

[ahjteam]

http://www.kvraudio.com/wiki/?id=FFT
http://en.wikipedia.org/wiki/FFT

[Martin E]

Thanks for the links but that doesn't clarify its use on audio for me very well. That is in layman terms. The question remains what's the purpose of using a fft filter on audio.

[ahjteam]

Thanks for the links but that doesn't clarify its use on audio for me very well. That is in layman terms. The question remains what's the purpose of using a fft filter on audio.

did you bother to read the "see also" section on wikipedia?

See also

* Cooley-Tukey FFT algorithm
* Split-radix FFT algorithm
* Prime-factor FFT algorithm
* Bruun's FFT algorithm
* Rader's FFT algorithm
* Bluestein's FFT algorithm
* Butterfly diagram - a diagram used to describe FFTs.
* Overlap-add - an efficient convolution method using FFT for long signals
* Spectral music (involves application of FFT analysis to musical composition)
* Spectrum analyzer - Instrument that use FFT

PS: IMHO those mathematical formulas are not for "laymans"

[Martin E]

Yes I did bother to look at it. But it's all Mumbo Jumbo to me. I don't have to know in detail how it works; nature science isn't exactly my strongpoint. I only want to know about its usefulness. Maybe I should have used other words to phrase the question.

[farlukar]

in layman terms

It's used in EQ

[Martin E]

in layman terms

It's used in EQ

I had that figured

[farlukar]

Seriously though - it's just a filtering algorithm, it splits your signal into a bunch of frequencies so you can change the level of separate frequencies.
Really nothing much more to it

[Martin E]

Seriously though - it's just a filtering algorithm, it splits your signal into a bunch of frequencies so you can change the level of separate frequencies.
Really nothing much more to it

Ok, thanks. That sheds some light.

[kylen]

You can download the free VST plugins from the Reaper folks if you want to play around with an FFT based FX machine:

http://reaper.fm/download.php

There's a plugin in there called reafir_standalone that gives you graph control (as opposed to a knob) of the FFT based digital machine allowing you to make adjustments in the frequency domain. Depending on the mode you have an EQ, COMP, GATE, etc. This little guy is along the same lines as the once mighty IONIZER (RIP-Arboretum) and still mighty REDUNOISE (Voxengo).

ED: Speaking of Google, the first couple of paragraphs of this article suit me (layman here):
http://www.mts.net/~mathers/q1_fft.html

Obviously the article would make most folks around here think of SPAN. There are also some fine time domain/frequency domain discussions at KVR (EFFECTS forum for one, I'll bet DEV forum too) that search will bring up.

[kristonics]

Asking questions in forums can be like walking on eggshells.

[Martin E]

ED: Speaking of Google, the first couple of paragraphs of this article suit me (layman here):
http://www.mts.net/~mathers/q1_fft.html

Thanks for the link

The first two sentences from this article probably sums it up.

How do I use FFT?

Talk about a difficult question....

[ohm]

In my music I don't use FFT based fx all that much because of the latency issues (I prefer to work in real time).
FFT works in buffers - the larger the buffer, the better the accuracy. Accuracy in this case can be compared to the bitrate of mp3's. So a low buffer size of 512 samples will sound like low bitrate mp3. If latency is no issue, just select a large buffer size and the sound quality is not compromised.

The most notable feature of an FFT eq is that it's the most accurate (as in what you see is what you get) way of eq'ing. If you highpass at 100hz you get an exact cut. Note that this doesn't mean it's the best sounding way of doing it. It's clean though as in surgical.

As a programmer I've only worked with FFT as a means of analyzing the sound - it's the best way to get accurate peak detection for slicing / tempo analysis. , so I'm not 100% sure about the audio quality issues when rebuilding audio from FFT "bins". I have been wanting to add some weird spectral effects to my slicer / sampler LiveSlice, because there I could simply precalculate the effects and maintain realtime capability.