Re: [Audacity-devel] Denoise / Declicking / Decrackle (was: GSoC Ideas)

[Gale A. <ga...@au...>]

| From Thomas Holzmann <ho...@gm...> 
| Sun, 16 Mar 2008 20:48:18 +0100
| Subject: [Audacity-devel] Denoise / Declicking / Decrackle (was: GSoC Ideas)
> > I think the main problem is FFTW not being GPL compatible, plus some 
> > adjustments would be needed to make the 16 bit functions work in 
> > 32 bit float. See Richard's comments:
> > http://www.nabble.com/Noise-Reduction-td13343112.html#a13358823
> >
> > Also as Leland pointed out a while ago, an older version of the denoise
> > function already exists as a library and doesn't appear to be encumbered by 
> > the license issue.  It still raises the question how useful it'd be by itself. 
> > The declick and decrackle functions are actually more important for 
> > cleaning up records and if we are looking to be useful, it is declicking 
> > that desperately wants improving, far more than noise removal (and 
> > decrackle that is entirely missing). 
> Do you mean an older version of the denoise function from the gwc 
> already exists as library? 

Yes that's what I meant according to what I understand from Leland.

> Does also the other functions already exist as library?

I believe not, or Leland would have mentioned them. 

> 
> I think I could extract the functions from the gwc and then use it as 
> library in audacity. I've made a quick look at the source code from gwc 
> and found out that the gwc computes some things with 16 bit integers and 
> some with 32 bit floats (especially the declick/denoise functions seem 
> to work with floats). So I think this should not be such a great problem.
> Also FFTW is (look at its webpage: 
> http://www.fftw.org/faq/section1.html#isfftwfree ) distributed under the 
> GPL and according to configure.in from gwc source it needs the following 
> libraries: alsa (GPL/LGPL), fftw3(GPL), sndfile (LGPL), libgnomeui(GPL). 
> So I think there should not be license issues.

OK it does seem that FFTW has become GPL from 1.3 - but what about
"Paul Bourke, who graciously allowed the use of his code to fit 
autoregressive coefficients using the maximum entropy method" -
might he have to be approached? Is this the non-GPL algebra code 
Richard mentioned?  Would the GWC owner be able to answer 
definitively on using the code in Audacity?


Gale