spectral reverser

Oct 3, 2010 at 11:18am

spectral reverser

Hi guys out there,
trying to build a spectral reverser, basically it take a spectrum and flips it on the frequency basis, highs become lows and the other way around. Was thinking of usinf pfft~, any simple idea how to do this?

#52561
Oct 3, 2010 at 3:50pm

hi,

i did that for an installation in amsterdam at sonic acts this year
http://www.steim.org/STEIMBLOG/?p=1481
(scroll down to “two rooms, flipped)
the route i took was millers sigmund~ object and then resynthesize with the frequencies flipped.
caveat: due to the logarithmic nature of the frequency perception, you have to tweak the output mathematically, otherwise you end up with just a high pitched hiss.
its a fun endeavour anyway.

hth
hans

#189047
Oct 4, 2010 at 9:50am

In my opinion you have to la’ a spandi ledam. Check if it is working…Good luck.

#189048
Oct 4, 2010 at 5:56pm

now thats advanced technology :-)
elisabatti could you explain a bit more, please?

thanks
hans

#189049
Oct 6, 2010 at 1:58am

if i understand well
bin 0 transformed to bin 511, bin 1 to 510 etc…
i have something like this…

the main idea is to store the input bins and then index them with the way you want (backwards)..

but don t expect something awesome..

Attachments:
  1. spek-rev.rar
#189050
Oct 8, 2010 at 4:11pm

Well Tada, i get only noise form your patch, should look at it now.. on the other hand Hans’ idea works fine and it’s rather easy.. one thing Hans, did you remap logarithmically the frequencies? which kind of tweaking did you find best? I guess it depends also on the material you use…

J

#189051
Oct 11, 2010 at 3:36pm

hi jester,

yes, i used a logarithmic mapping based on lp.scampf (litter starter pack) and manually tweaked it until it sounded good for my purpose. (as a reference soundfile i used a snippet of the poplvetsian dances by borodin. easy to hear leaps in the melody and then have them jump in the opposite direction while retaining some of the soundqualities).

i also wasn´t able to get much out of tadas example (which otherwise seems like a very elegant approach). maybe have to study it more carefully.

hans

#189052
Oct 11, 2010 at 11:58pm

hey… ive been reading you are working with the spectrums… do you know any patch that can “read” images and reproduce them as sound?
thanks a lot.
martín

#189053
Oct 12, 2010 at 7:36am

hi martin,

actually i am not sure i understand what you want.
image to sound: either openraw in soundfile or search in the jitter forum, loads of posts about that.

or did you have somethng specifc in mind using spectrums?

hans

#189054
Oct 17, 2010 at 10:58pm

Hi hans, sorry for taking so much time to answer but i had to work far away from the computer jej. Thanks very much for your answer.

I´ve been looking for that in jitters´forum but i couldnt find any solution.

In order to leave things clear, i want “something” to read this scaned image of a “thread” (a thread used for packaging the pizza jej) like if it was a sound wave (check the attachment).

Any ideas?
I have found one that can record sound, show the spectrum and reproduce that spectrum in loop. but it doesnt work for “long-lasting” images nor for other non-spectrum iamges.

Nice week!
Martin

[attachment=143854,1250]

Attachments:
  1. Imagen_1.png
#189055
Oct 19, 2010 at 7:47am

Your question is confusing. You want to translate this image into a waveform, right? Check [jit.buffer~] (of course, you’ll need to know about Jitter, matrices, and stuff like that). But you talk about spectrum: this is a different subject. As far as I understand, you don’t want to work in spectral domain, rather play back a waveform, right?

#189056
Oct 19, 2010 at 11:53am

What you could try is to build a vocoder and reverse te connection between the analysing and modulating part. The synton Vocoder could do this with a matrix. I tried this and it works fine. Also, you have more control since you can manipulate the matrix to alter the sound to your liking.

Not FFT but a workable solution.

#189057
Oct 19, 2010 at 10:46pm

i think elmarta is looking for an image to spectrogram patch, where the frequency bins are mapped on the y-axis, the color determines the strength of each frequency bin (the z axis) and time is the x-axis. I saw MATLAB code that did this once and it was awesome, but don’t have the code myself. Would love to see a max version. Could try to code it myself when I have a bit more free time.

#189058
Oct 25, 2010 at 1:25am

Hey.. thanks for the answers :)
As you can see Im new at this.

Its good for me that my question has been interpretated in different ways so that it gives me some chance to imagine how to solve it.

I want to playback a waveform, as Jean-Francois Charles said (thanks for your answer, i ve read your article and downloaded the patches). The x axis=time, y=frequence, as ComfortableInClouds said but Z=¿? (there is no color variable though its a scan of a white thread commonly used to wind up pizza box).

Danny im sorry but I dont know how to use matrices. I was thinking on this process.. import an image, read the contour )using black and white contrast) and reproduce it as if it was a waveform. Some variables i want to manage are: length and height of the imported image so to manage duration and frequency in the resulting sound. Here im trying to assume some parallelism between distance and time (1cm to 1sec); and height and frequency.

Any tutorial from where i can learn how to start doing this? Thanks a lot for the time you take to understand what im trying to say and for the help :)

Again, Nice week jeje
Martin

#189059
Oct 2, 2013 at 5:11pm

has anyone implemented a spectral reverse with the logarithmic curve, not using third-party externals? i’m not entirely sure how to do this..

#266897
Oct 24, 2013 at 2:01am

I caved in and started using tap.spectra~ – but I’d really like to implement a log. response in it- any ideas?

#268977

You must be logged in to reply to this topic.