Re: [Linuxsampler-devel] Sampler quality comparison...

[<be...@ga...>]

I agree with Sebastien here, resampling by too big factors causes
bad shifting of formants even if you use the highest quality 
resampling method and natural instruments would sound very bad.
(try to span a piano sample over 2 octaves or so).

sfz+ uses bandlimited interpolation which is very high quality
(no aliasing if you upsample high frequency content) but this method
of interpolation can consume an unlimited amount of CPU as you
go higher with resampling factors.
I think cubic interpolation is the best compromise because it is 
fast and offers good quality when downsampling or upsampling in ranges
where you don't hit the nyquist frequency. 
eg a 15KHz sine upsampled by 1 octave (played at speed factor 2) would
sound good with bandlimited interpolation since it would filter
the frequencies above 15kHz.
15KHz * 2 = 30kHz, apply the samplerate/2 (about 20KHz) filter and
what you get is silence, which is better than those ghost frequencies
eg (22 - 15 = 7kHz).
But as Sebastien said, if you sample each 2-5 semitones you don't run
into these problems plus you avoid that too much formant shifting causes
unnatural sound.

cheers,
Benno
http://www.linuxsampler.org



Scrive Sebastien Metrot <me...@me...>:

> Sorry to get out of my hole but i think this study is pretty stupid and 
> ignorant of the actual purpose of a sampler. The purpose of a sampler is 
> to replay samples as close to their sampling frequency as possible in 
> order to acheive a high level of realism. If you want synthesis then 
> this is a whole diferent issue, and then high quality resampling with 
> filtering and multipoint interpolation not only makes sense but is also 
> a must. However in most cases linear interpolation is really good enough 
> for samplers. If you want to use your sampler as a sound creation tools 
> you WILL use the artifacts. Except this case, no sane sound bank 
> designer would use a sample more that 5 halftones from its root key 
> (actually 1 or 2 seems to be the standard).
> 
> Sebastien
> 
> 
> Tobias Erichsen wrote:
> 
> >Hi everyone,
> >
> >just came by the following site, which compares the quality of the
> >resampling-algos in the different samplers.
> >
> >Thought that perhaps this might be interesting...
> >
> >http://www.djlaser.com/public/samplers/
> >
> >Best regards,
> >Tobias
> >
> >
> >
> >  
> >
> 
> 
> 
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