[PD] Re: [PD-dev] i need some help with this

J. Scott Hildebrand jshildebrand at ucdavis.edu
Wed Sep 4 22:50:19 CEST 2002


        the goal is to come up with a very fast convolution algorithm, in
real-time. i'd like to use pd because it has very useful DSP and the
ability to make somewhat of a useable interface. it's not as clean as a
GUI done using C++ libraries, but it'll work fine for my purposes. right
now my impulse responses are 200 samples long, but later on i need to
implement longer floor/wall reflections. add to this head tracking and GEM
to display it all in beautiful 3-D. at the moment i'm stuck trying to
figure out the DSP details of pd, which puts all the other things on the
backburner. i guess that's it. oh yeah on the side i'm sorta working on a
project that will be a great demonstration of pd. it'll be aimed at
computer science & music academically-oriented people.

        i learned just the basics of csound in an electronic music class,
but i think pd is much more useful and can do a better presentation of
synthesis to students. that's not exactly my department though; the main
thing i'm trying to do is replace expensive hardware DSPs with a good
software version. it'll be cool when it's done :) i'll be sure to post it
to the list, put it on an ftp, or put it in the external vault.

                                                 scott


On Wed, 4 Sep 2002, marius schebella wrote:

> scotty, beam me up a little!
> you can have the convolution process on two given audio wave-files, thats
> one thing, but also on streaming data. and the fft-windows can be smaller
> than the samples or bigger (twice as big, if you like.)
> it is like a reverb: you can wait until the reverberation of a soundfile is
> finished or just play and play...
> the first method could make sense if you have very long and complex
> wavefiles to have a clean special effect without any glitches or loops. the
> problem with this method is the handling of large files and a lot of cpu is
> needed. this cannot be done in realtime, because you only can listen to the
> sound, if the calculation has finished, but of course it can be done in
> pd...
> with the other method you split the wave files in slices and convolute
> always small parts. this is something different. after the convolution they
> are put together again.
> hmm, can you explain again, what you want to do, which sounds to use, ...?
> marius.
>
>
>
>
> ----- Original Message -----
> From: "J. Scott Hildebrand" <jshildebrand at ucdavis.edu>
> To: <zmoelnig at iem.at>
> Cc: "J. Scott Hildebrand" <jshildebrand at ucdavis.edu>; <pd-dev at iem.kug.ac.at>
> Sent: Tuesday, September 03, 2002 9:08 PM
> Subject: Re: [PD-dev] i need some help with this
>
>
> >
> >        i wouldn't mind at all to do the convolution with the built-in fft
> > stuff. the only problem is that i don't quite understand how it works.
> > what i need is to input x amount of samples, and get out y amount of
> > output, which should be at least 1.5 times the original amount + padded
> > zeros to equal 2 times the original amount. only then can i write an
> > overlap and add method.
> >
> >                      scott
> >
> > On Sat, 31 Aug 2002 zmoelnig at iem.at wrote:
> >
> > > hi scott !
> > >
> > > i really recommend that you read the mail i send you when qou first
> posted your
> > > piece of code.
> > > i really tried to point out all the faulty pieces of code (especially
> the
> > > neveroccuring reset of apple)
> > > and i again give you one advice: add debugging code like "post()" to
> show you
> > > where the error occurs !
> > >
> > > i am not going to do the programming for you (and i hope no one else
> will do)
> > > - just read the mails. (it's all in there)
> > >
> > > and again:
> > > is there any major reason not to do the convolution as an abstraction ?
> > > to not use pd's built in fft-routines ?
> > >
> > >
> > > mfg.cd.sar
> > > IOhannes
> > >
> >
> >
> >
> >
> > --------------------------------------------------------------------
> >
> > "640K ought to be enough for anybody." -- Bill Gates, 1981
> >
> > --------------------------------------------------------------------
> >
> >
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> > PD-dev at iem.kug.ac.at
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>
>
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