Re: [linux-audio-dev] Resampling

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Subject: Re: [linux-audio-dev] Resampling
From: Richard Dobson (RWD_AT_cableinet.co.uk)
Date: Thu Aug 02 2001 - 14:12:53 EEST


The Csound pvoc has many differences from others, not least in that it
offers time-scaling by means of interpolating between the analysis
frames of the pre-created analysis file. It is not a simple streaming
pvoc the way others are.
I suspect there are other aspects too where the implementation couyld be
improved. More orthodox pvocs, sucha s the F.R Moore one, and CARL (on
which my 'PVStream' real-time pvoc is based), does offer exact
reconstruction. Because of the interpolation, Csound pvoc probably never
gives an exact reconstruction.

Richard Dobson

Nick Bailey wrote:
>
> Juhana Sadeharju wrote:
>
> > OK. I have been quite skeptical to any FFT analysis/synthesis because
> > the phase vocoder in Csound sounds very muddy even no change is done.
>
> Something's wrong. Overlap? Window shape?
>
> > But if you're handling only the complex values got from FFT (not amplitude-
> > phase versions), then everything should be better.
>
> And the difference would be.....?
>
> You can express the complex in either rectangular form (z = x+jy) or polar
> form (r.cos t + j.r.sin t) -- it makes no difference which you use.
>
> If it does, there's a bug somewhere 8-) The FFT is strictly invertable, and
> you should get exactly the same numbers out as you put in. Whether the
> "spectrum" is "correct", well, that's another story.
>
> N./

-- 
Test your DAW with my Soundcard Attrition Page!
http://www.bath.ac.uk/~masrwd (LU: 3rd July 2000)
CDP: http://www.bath.ac.uk/~masjpf/CDP/CDP.htm (LU: 23rd February 2000)


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