[sc-users] Re: Help me map a control rate signal with a buffer

[Carlo Capocasa <theman@xxxxxxxxxxxxxxxxx>]

Hi again Dan!

Thanks again for your helpful reply, your method is working like a charm.

I'm mapping a signal in equal temperament onto the same signal as if 
played using just intonation. What's great is, I used the MIDI note 
value as an index creating the buffer (happened to have that function 
lying around), so it has human-readable meaning as well *so proud*.

Here's the code, just in case some Googler will find it useful some day.

Carlo

/*

Code for mapping a signal played by an equal temperament instrument
as if it had been played using just intonation.

Source of Just Intonation intervals: en.wikipedia.org/just_intonation

(c) 2009 Carlo Capocasa.

Released under the MIT license.

*/

var
  basefreq = 450,
  baseoctave = 6,
  scaletones = 12,
  just_intonation = [1, 256/243, 9/8, 32/27, 81/64, 4/3, 729/512,
                     3/2, 128/81, 27/16, 16/9, 243/128],
  scale_equal_temperament = {
    arg note;
    1.0594631 ** note;
  },
  scale_just = {
    arg note;
    just_intonation[note];
  },
  freq = {
    arg num, scaleFunction = scale_just;
    var
      note = num % scaletones,
      octave = (num - note) / scaletones,
      interval = scaleFunction.(note),
      octfreq = basefreq * (2 ** (octave-baseoctave));
    octfreq * interval;
  },
  mapping = (
    'just':      Buffer.alloc(s,127),
    'tempered':  Buffer.alloc(s,127)
  );

/*

Use this in a synthdef, where freqs is the frequency
of the instrument as control rate:

  arg freq;
  var mapindex;
  mapindex = IndexInBetween.kr(mapping['tempered'],freq);
  freq = IndexL.kr(mapping['just'],mapindex);

*/



Dan Stowell wrote:
> It's just linear interpolation. e.g. if the input is 12.53 and the
> buffer contains [11,12,13] then the output is 1.53, where the "1" is
> because it's somewhere between indices numbered 1 and 2, and the ".53"
> is reverse-linear-interpolation:
> frac = (input-b[1]) / (b[2]-b[1])
>
> Dan
>
> 2009/5/3, Carlo Capocasa <theman@xxxxxxxxxxxxxxxxx>:
> > Hi Dan!
> >
> >  Thanks, that sounds really helpful. Can you explain something about this?
> > How is the interpolation done, IE how does the program 'know' how far in
> > between the elements of ~from the signal was at any given point?
> >
> >  Thanks a lot for your reply,
> >
> >  Carlo
> >
> >
> >  Dan Stowell wrote:
> >
> > > Hi Carlo -
> > >
> > > One way you can do it is using IndexInBetween to "unmap" your input
> > > into integer slots, and then use IndexL to do the reverse, to "map"
> > > onto your other distribution. This example maps a sort-of-exponential
> > > curve onto a sort-of-sinusoidal curve:
> > >
> > > ~from = [1, 2, 4, 8, 16];
> > > ~to   = [0, 1,  0,  -1,    0];
> > > x={IndexL.kr(~to.as(LocalBuf),
> > IndexInBetween.kr(~from.as(LocalBuf),
> > > MouseX.kr(~from.first,~from.last).poll).poll).poll}.play
> > >
> > > HTH
> > > Dan
> > >
> > >
> > > ---------- Forwarded message ----------
> > > From: Carlo Capocasa <theman@xxxxxxxxxxxxxxxxx>
> > > Date: 3.5.2009 11:35
> > > Subject: [sc-users] Help me map a control rate signal with a buffer
> > > To: sc-users@xxxxxxxxxxxxxxxx
> > >
> > >
> > > Hi! Thanks for reading. I'm looking for some help... I need to
> > > re-shape a control rate signal with a mapping function defined by a
> > > series of float (X|Y) values and linear interpolation in-between.
> > > Using a buffer seems to be the most elegant way to do this, could you
> > > kindly point me to Ugens that might do this? IndexInBetween seemed
> > > promising but then the X-Values have to be integers. Thanks!
> > >
> > >  Carlo
> > >
> > >
> > >  _______________________________________________
> > >  sc-users mailing list
> > >
> > >  info (subscription, etc.):
> > http://www.beast.bham.ac.uk/research/sc_mailing_lists.shtml
> > >  archive:
> > https://listarc.bham.ac.uk/marchives/sc-users/
> > >  search:
> > https://listarc.bham.ac.uk/lists/sc-users/search/
> > >
> >
> >  _______________________________________________
> >  sc-users mailing list
> >
> >  info (subscription, etc.):
> > http://www.beast.bham.ac.uk/research/sc_mailing_lists.shtml
> >  archive: https://listarc.bham.ac.uk/marchives/sc-users/
> >  search:
> > https://listarc.bham.ac.uk/lists/sc-users/search/


_______________________________________________
sc-users mailing list

info (subscription, etc.): http://www.beast.bham.ac.uk/research/sc_mailing_lists.shtml
archive: https://listarc.bham.ac.uk/marchives/sc-users/
search: https://listarc.bham.ac.uk/lists/sc-users/search/