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List:       kde-multimedia
Subject:    Re: Improving sound through aRTs
From:       Stefan Westerfeld <stefan () space ! twc ! de>
Date:       2000-12-12 21:52:58
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   Hi!

On Wed, Dec 06, 2000 at 09:23:23AM -0500, nbecker@fred.net wrote:
> I have a lot of expertise in DSP.  Yes, "linear" interpolation
> (actually, you mean 2 point linear interpolation) is not very good.
> But you don't need an infinite length sinx/x either.
> 
> Actually, if you want to use a linear interpolator all you need is any
> lowpass filter that will handle your passband and has reasonable
> attenuation for the aliased images.  It may only need a few taps to do
> this.
> 
> One simple alternative is a nonlinear device, called Lagrange
> interpolation.  This is a very simple algorithm that is quite
> effective in many cases.
> 
> Maybe I can help out.

That would be great. Well, I have posted already what I would think would
be the optimal solution (generic resampling/conversion algorithms which
replace both convert.cc/resample.cc). But actually, you could also have
a look at improving the existing resampling code.

When I wrote them, I thought linear interpolation should be good enough,
but obviously I am wrong ;) - so if you just fill in some code in resample.cc
to make it sound better, you would probably already improve the current
solution quite a bit. As long as people with little CPU power can turn it
off, that would be a good first step. The code in convert.cc might be a bit
harder to adapt, because it uses lots of macro magic.

   Cu... Stefan
-- 
  -* Stefan Westerfeld, stefan@space.twc.de (PGP!), Hamburg/Germany
     KDE Developer, project infos at http://space.twc.de/~stefan/kde *-         
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