Re: [Audacity-devel] Equalizer problem - Fixed (mostly)

[Markus M. <me...@me...>]

Hi Martyn,

this is awesome!! Do you have a patch file against CVS HEAD for that, so 
I can integrate it?


Markus

Mar...@ao... schrieb:

> Hi all,
>  
> Particularly those interested in the problem with the Equalizer that 
> was reported back in April and discussed at length (particularly 
> window lengths!).
>  
> I have located the root cause of the problem and why it shows up in 
> 'Equalizer' but not in 'FFT Filter'.  I believe (and can see) that my 
> fix also fixes the 'Spectrum' view which (I had not reported this as 
> an error and don't know if anybody else had) gives spurious horizontal 
> lines even when you generate a perfect sinusoid.
>  
> The core of the FFT routine uses 'float' when it should be using 
> 'double' (at least). The build up of errors for longer block lengths 
> is significant and causes the problems. 'FFT Filter' uses a (hard 
> coded) length of 256, and the problems are insignificant whereas 
> 'Equalizer' uses a (hard coded) block length of 16384, which causes 
> significant build up of errors, it would appear.  I have not done 
> analysis to find out which of the variables is most significant and 
> boldly changed about 11 of them.
>  
> I have given more details at http://members.aol.com/MartynShaw/ and a 
> fixed windows exe. I don't mind discussing my findings should you have 
> any queries at all.
>  
> HTH
>  
> Martyn
>  
> PS Are there any other 'signal processing' type bugs/errors/queries 
> that I can get my teeth into?