Subject: [ecasound] Re: [linux-audio-user] LADSPA Module (fwd)
From: Kai Vehmanen (kai.vehmanen_AT_wakkanet.fi)
Date: Sat Dec 08 2001 - 18:42:38 EET
It seems that it actually _is_ is possible to change tempo without
changing pitch with ecasound!
---------- Forwarded message ----------
From: Kai Vehmanen <kai.vehmanen_AT_wakkanet.fi>
Subject: Re: [linux-audio-user] LADSPA Module
On Fri, 7 Dec 2001, Andy Wingo wrote:
>> * change the speed of a wave without changing pitch ???
> No. To do this, you would have to read data at a different rate than you
> write it. In order to get this effect, you need to have a ladspa host
> that can change the speed by resampling then adjust the pitch with
> steve's plugin. Experts correct me if I've erred on this one ;)
Hmm, interesting idea. How about:
ecasound -i foo.wav -o /dev/dsp -ei:200 -el:pitchScale,0.5 -c
... -ei is ecasound's own pitch-shifter, which actually is just a
resampler. With '-ei:200' it takes 'x' samples as input, and outputs 'x/2'
samples. Then we lower the pitch with Steve's pitchScale LADSPA-plugin,
which unlike -ei is FFT-based. The result: same pitch but double tempo!
Unfortunately slowing down doesn't seem to work due to a bug in
ecasound's LADSPA support. Ecasound's CVS-tree has the fix. Then you can
ecasound -i foo.wav -o /dev/dsp -ei:75 -el:pitchScale,0.90
PS 'foo.wav', Dave Brubeck's Take Five, is a bit hectic at
double speed. On the other hand it's still a lot better than
the chipmunk mix with only -ei:200. ;) For very weird pitch-shifting,
try "ecasound -i foo.wav -o /dev/dsp -pn:chipmunk" and
"ecasound -i foo.wav -o /dev/dsp -pn:stretched_tape".
If you're using ecasound's CVS-version, then it's
-pn:var_chipmunk and -pn:var_stretched_tape...
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