Hi Simon, list,
On 04/08/16 22:51, Simon Iten wrote:
hi claude,
your bandlimited project works/sounds great! very nice sounds from handdrawn waves.
thanks!
however i am having trouble getting your example to work. probably just stupidity from my side.
i suppose i don’t understand your:
"set appropriate block size, turn off dsp, bang to execute 1 block”
message. if you find the time, can you have a look at it?
sure, just a [loadbang]--"0"--[switch~] - this turns off dsp for the canvas (so you might want to put it all in a subpatch unless you're using it as an abstraction). see attached, works for me
do i not need to run a bang into tabplay in this special one block send scenario?
with my patch i get “kind" of the right thing.
- the table “spectrum” only updates once i click into the table (after i hit
the bang).
mm, seems to be a Pd bug or other infelicity. the attached includes a workaround using [tabwrite] which updates the GUI
- i get only 64 values, so i guess my blocksize is still 64?
no, it's that for real signals the second half of the rfft~ output is symmetric to the first, so Pd sets it to 0 and ignores it in rifft~ to avoid confusion.
- if i send a bang to switch~ when dsp is off, i get an error on the console:
bang to block~ or on-state switch~ has no effect.
you have to switch it off with "0" first, and have global dsp on (afaik).
cheers
hth,
Claude
On 04 Aug 2016, at 18:01, Claude Heiland-Allen <claude@mathr.co.uk mailto:claude@mathr.co.uk> wrote:
Hi Simon,
On 04/08/16 09:54, Simon Iten wrote:
ah sorry, yes
i want to read a wavetable, say 128 steps and calculate the gain structure to aproximate this wavetable with sine waves. the idea behind this is to get a different sound from wavetables, use low resolution wavetables to get nice sounds (waldorf microwave xt)
so for a saw wave i would want the following numbers.
1 0.5 0.3333 0.25 0.2 and so on…
how to do this for an arbitrary input wavetable?
i looked at the fft examples but it is not clear to me how i would do this with a single wavetable (of known size)
You could do something like this with [rfft~], but you lose phase information which might be important depending on what you are doing (use fixed-width font to see diagram):
"set appropriate block size, turn off dsp, bang to execute 1 block" | [switch~]
[tabplay~ wavetable] | [rfft~ ] ^ ^ [*~] [*~] \ / [+~] | [sqrt~] | [tabsend~ spectrum]
or if there is a “simpler” (without fft) possibility that would be great.
I don't think you'll get simpler than FFT here. As a bonus you can also get phase information (sinesum has all phases 0, cosinesum all phases pi/2, general wavetable can have arbitrary phases).
You could use [rifft~] instead of sinesum to generate your wavetable, too. Note there may be some issues with normalization (fft->ifft has an amplitude gain equal to the blocksize, iirc).
For a more advanced use of oneshot FFT and IFFT for wave tables, see my bandlimited project: https://mathr.co.uk/blog/2015-02-12_bandlimited_wavetables.html
Claude
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