Subject: [linux-audio-dev] Resampling
From: Alexander Ehlert (alexander.ehlert_AT_uni-tuebingen.de)
Date: Wed Aug 01 2001 - 15:22:41 EEST
Hi Juhana,
sorry with all that gui discussion I totally forgot about this email.
> What exactly is the algorithm? Does it do a good job? How have you
> tested it?
I just do an n-times oversampling DFT. You can configure blocksize
and oversampling(overlap) factor. Then for the resampling process
I just add/remove bands in the frequency domain and then do resynthesis.
Thats it. In the oversampling and resynthesis code I use Hanning windows.
It's all done in float precision atm. For FFT I use the fftw lib, which
is really fast. So I can do 32times oversampling with 16384 samples
blocks in realtime on a celeron 300. But you don't really need that
8-times oversampling with 1024 samples windows is really enough to
get good sounding quality. I never did a frequency analysis on my
results, only listening tests and I like the result. If someone
feels like thoroughly analyzing it, go ahead :)
> turning Glame's wave editor, Sweep and Audacity(?) to a SoundForge
> clone because SoundForge has a quite good user interface. I understand
I don't know about that. But I don't want to get in that GUI discussion
again. It has some nice features, like nice windows for analyzing and
applying effects. We'll have that soon too :)
BTW: Yesterday I gave my flanger effect some polishing, you can now
change parameters realtime and it has a nice feedback and gain control.
Just using it at the limit just before it turns into an oscillator the
effect sounds really cool on voice. No it's not a ladspa plugin.
Linuxtag people may remember the mickey mouse/darth vader effect I did
with that effect. That still works, but I have to separate that into
a detuner soon to remove the anoying clicks. Those clicks are additional
to the ones trying to do realtime/lowlatency stuff with ALSA.
Is there any card, that works fine with full duplex 44kHz and small
fragment sizes? Not the Hammerfall, I want something cheaper.
Or does someone know a cheaper AD/DA converter than the RME one?
Surprisingly the cheap Ensoniq cards work quite well :)
Cheers, Mag
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