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

J. Scott Hildebrand jshildebrand at ucdavis.edu
Thu Sep 5 00:38:02 CEST 2002


         hey marius,

            thanks a bunch for the patch. i've spent some time going
over it and i think that it'll definitely be possible to modify this a
little and make it work. i understand the organization of it but i do have
some questions. i don't have any EE background!

            you have [; filterarray const 0] in a message box; does that
initialize the elements to 0? and don't i need to create a filterarray
array? right now there's 5 arrays, all labeled array1 - array5, but they
are all each 100 in size. wouldn't i just need two of those that are of
size 256? and then two more size 256 arrays for the filters?

            when the actual convolution is happening, i don't quite
understand why i need to use the complex portion of the output. don't i
just use the left output of the rfft~ for and then multiply the real
portions?

	    why do i have subtraction on one side and addition on the
other?

            i'm not too sure about why i need to do the normalization
either.

            and one more thing, when it finally outputs back to the
overlapnadd window there's an input comparing thing. that's just to graph
the waveforms right? ok that's it for now. i do appreciate the help
immensely, and if anybody is startled by my childishly simplistic
questions, well my excuse is that i was dropped a few times when i was an
infant :)

                                  k thanks,

                                                scott

On Wed, 4 Sep 2002, marius schebella wrote:

> hi scott.
> i made an example of what i think you want to do. please tell me, if i'm
> wrong. you can draw a filterkernel of 128 samples (time-domain!) and
> convolute it with any sound you like, ... you can adapt this to your own
> needs.
> see attached patch.
> 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
> >
> > --------------------------------------------------------------------
> >
> >
> > _______________________________________________
> > PD-dev mailing list
> > PD-dev at iem.kug.ac.at
> > http://iem.kug.ac.at/cgi-bin/mailman/listinfo/pd-dev
>




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