Non – realtime (offline) FFT-IFFT options?

Jan 10, 2008 at 12:41pm

Non – realtime (offline) FFT-IFFT options?

Hi Everybody,

I am looking for a way to perform a non-realtime FFT/IFFT, I know how to do the realtime stuff with pfft~ etc. but I want to perform a FFT on a buffer~ wich is not longer than the FFT size. So basically I want to use it for analysing a buffer and I can’t see how to do this with the realtime stuff. I’ve also searched maxobjects.com where I find a lot off realtime stuff, but no offline stuff.

Thanks a lot,
Kessito

#35299
Jan 10, 2008 at 2:04pm

Hi Kessito,

This should be possible with FTM, from IRCAM, although I don’t know
offhand what the maximum FT size is.


Owen

Kessito wrote:
> Hi Everybody,
>
> I am looking for a way to perform a non-realtime FFT/IFFT, I know how
> to do the realtime stuff with pfft~ etc. but I want to perform a FFT
> on a buffer~ wich is not longer than the FFT size. So basically I
> want to use it for analysing a buffer and I can’t see how to do this
> with the realtime stuff. I’ve also searched maxobjects.com where I
> find a lot off realtime stuff, but no offline stuff.
>
>

#120184
Jan 10, 2008 at 2:48pm

You can use soundhack for this and then read the result with csound~
external.

Peiman

On 10 Jan 2008, at 14:04, Owen Green wrote:

> Hi Kessito,
>
> This should be possible with FTM, from IRCAM, although I don’t know
> offhand what the maximum FT size is.
>
> —
> Owen
>
> Kessito wrote:
>> Hi Everybody,
>> I am looking for a way to perform a non-realtime FFT/IFFT, I know how
>> to do the realtime stuff with pfft~ etc. but I want to perform a FFT
>> on a buffer~ wich is not longer than the FFT size. So basically I
>> want to use it for analysing a buffer and I can’t see how to do this
>> with the realtime stuff. I’ve also searched maxobjects.com where I
>> find a lot off realtime stuff, but no offline stuff.
>> maxmsp mailing list maxmsp@cycling74.com http://www.cycling74.com/
>> mailman/listinfo/maxmsp
>
>

#120185
Jan 10, 2008 at 4:36pm

Is there a reason you can’t use the same [pfft~] methods, with
appropriate modifications, on a buffer instead of the real-time input
stream?

On Jan 10, 2008, at 5:41 AM, Kessito wrote:

>
> Hi Everybody,
>
> I am looking for a way to perform a non-realtime FFT/IFFT, I know
> how to do the realtime stuff with pfft~ etc. but I want to perform
> a FFT on a buffer~ wich is not longer than the FFT size. So
> basically I want to use it for analysing a buffer and I can’t see
> how to do this with the realtime stuff. I’ve also searched
> maxobjects.com where I find a lot off realtime stuff, but no
> offline stuff.

—-
Steven M. Miller
Professor, Contemporary Music Program
College of Santa Fe

Home < http://pubweb.csf.edu/~smill>
SFIFEM <
http://sfifem.csf.edu>
Atrium Sound Space <
http://atrium.csf.edu>
OVOS <
http://pubweb.csf.edu/~smill/ovos.html>
CMP <
http://www.csf.edu/academics/contemporary_music/>

#120186
Jan 10, 2008 at 6:45pm

#120187
Jan 12, 2008 at 12:11am

Kessito wrote:
> Hi Everybody,
>
> I am looking for a way to perform a non-realtime FFT/IFFT, I know how to do the realtime stuff with pfft~ etc. but I want to perform a FFT on a buffer~ wich is not longer than the FFT size. So basically I want to use it for analysing a buffer and I can’t see how to do this with the realtime stuff. I’ve also searched maxobjects.com where I find a lot off realtime stuff, but no offline stuff.
>
> Thanks a lot,
> Kessito

there is an external library called vasp (information is here:
http://grrrr.org, download is there: http://grrrr.org/ext/beta/max)
which does non realtime processes on buffers.) threaded and non threaded.
marius.

#120188
Jan 14, 2008 at 8:02pm

On 12 Jan 2008, at 01:11, marius schebella wrote:

> Kessito wrote:
>> Hi Everybody,
>> I am looking for a way to perform a non-realtime FFT/IFFT, I know
>> how to do the realtime stuff with pfft~ etc. but I want to perform
>> a FFT on a buffer~ wich is not longer than the FFT size. So
>> basically I want to use it for analysing a buffer and I can’t see
>> how to do this with the realtime stuff. I’ve also searched
>> maxobjects.com where I find a lot off realtime stuff, but no
>> offline stuff. Thanks a lot,
>> Kessito
>
> there is an external library called vasp (information is here:
> http://grrrr.org, download is there: http://grrrr.org/ext/beta/max)
> which does non realtime processes on buffers.) threaded and non
> threaded.
> marius.

also i have an external that does fft/ifft on buffers in non realtime
that i would be happy to share.
osx only.
vb

#120189
Jan 14, 2008 at 10:38pm

since vasp seems to be completely undocumented for max/msp right now, I’m sure a lot of people could make good use of your object, Volker.
Would you consider putting a link to it on maxobjects.com?

Regards,
Klaas-Jan

#120190
Jan 15, 2008 at 12:20pm

Thank you all for the replies, I will check out the vasp and ftm options. The reasons why I can’t do it with fft~/pfft~ are:
- It seems impossible to get a proper synchronisation between the buffer~ and the fft~ object (you can’t make a zero delay feedback)

-For this project I need FFT sizes of approx. 4 million points, to my knowledge the fft~ object has a maximum size of 16k.

#120191
Jan 15, 2008 at 12:26pm

On 14 Jan 2008, at 23:38, Klaas-Jan Govaart wrote:

>
> since vasp seems to be completely undocumented for max/msp right
> now, I’m sure a lot of people could make good use of your object,
> Volker.
> Would you consider putting a link to it on maxobjects.com?

ok -
i wonder how well this works for others anyway.
i’ve hesitated to put my stuff on maxobjects.com, cause most of the
objects were made for a specific project or simply for
proof of concept and therefore haven’t been tested very carefully, yet.
but since this state might not change “in the near future”, i might
aswell just make them available as they are, and let
everyone else decide what is useful and what not.

will probably find some time tonight to upload. stay tuned.
volker.

#120192
Jan 15, 2008 at 2:36pm

#120193
Jan 15, 2008 at 8:11pm

No, I’m afraid that I really do need this 0,01 Hz resolution, this is because I’m doing some very low-frequency analysing according to
type 0 (lab) ISO specifications… I know that I can just lower the sample rate but I need the whole spectrum, and I could do split frames (different sample rates for different parts of the spectrum) but then things might get dodgy when I FFTconvolve stuff.

What I actually need to do is:
-record log freq sweep (couple of minutes)
-convolve with inverse sweep ->this gives the impulse response
-filter with passband filters
-make energy decay curves

btw, maybe someone has actually used vasp, and could tell just how to perform a FFT/IFFT with it?

#120194
Jan 15, 2008 at 10:39pm

Hi Kessito,

You might find this helpful:

http://www.notam02.no/notam02/prod-prg-mammut-e.html


Owen

Kessito wrote:
> No, I’m afraid that I really do need this 0,01 Hz resolution, this is
> because I’m doing some very low-frequency analysing according to type
> 0 (lab) ISO specifications… I know that I can just lower the sample
> rate but I need the whole spectrum, and I could do split frames
> (different sample rates for different parts of the spectrum) but then
> things might get dodgy when I FFTconvolve stuff.
>
> What I actually need to do is: -record log freq sweep (couple of
> minutes) -convolve with inverse sweep ->this gives the impulse
> response -filter with passband filters -make energy decay curves
>
> btw, maybe someone has actually used vasp, and could tell just how to
> perform a FFT/IFFT with it?
>
>

#120195
Jan 16, 2008 at 12:12am

#120196
Jan 16, 2008 at 2:49pm

#120197
Jan 16, 2008 at 3:24pm

#120198
Jan 17, 2008 at 5:20pm

#120199

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