Forums

ifft in C/C++

Started by Parlous August 16, 2003
I have used FFTW for my fourier operations in the past, but is there a
inverse fourier transform library of some sort out there that is just as
fast?


Parlous wrote:
> > I have used FFTW for my fourier operations in the past, but is there a > inverse fourier transform library of some sort out there that is just as > fast?
FFTW can already do that. Why would you want another library? Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ "The Internet interprets censorship as damage, and routes around it." - John Gilmore, EFF co-founder
well, holy snot balls. i was unaware that going from "complex to real" in
the fftw meant an inverse transform. i ignored it when i was concerned with
the fft only, thinking it had to do something with going forward/backward
meaning postive versus negative frequencies!

whelp, things like that happen when you're totally new to the dsp world i
guess!

"Parlous" <parlous@hotmail.com> wrote in message
news:vjt4cs2aidp0ee@corp.supernews.com...
> > I have used FFTW for my fourier operations in the past, but is there a > inverse fourier transform library of some sort out there that is just as > fast? > >
Parlous wrote:
> > well, holy snot balls. i was unaware that going from "complex to real" in > the fftw meant an inverse transform. i ignored it when i was concerned with > the fft only, thinking it had to do something with going forward/backward > meaning postive versus negative frequencies!
Its been a while since I last looked at FFTW, but I believe that you need to use the FFTW_BACKWARD flag to get the inverse FFT. I also seem to remember that you still need to do the scaling by 1/N yourself. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ "I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours." -- Stephen Roberts
Erik, I like your sig.

	- Eric


On Sat, 16 Aug 2003 22:48:12 GMT, Erik de Castro Lopo
<nospam@mega-nerd.com> wrote:

>Its been a while since I last looked at FFTW, but I believe that >you need to use the FFTW_BACKWARD flag to get the inverse FFT. >I also seem to remember that you still need to do the scaling by >1/N yourself. > >Erik >-- >+-----------------------------------------------------------+ > Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) >+-----------------------------------------------------------+ >"I contend that we are both atheists. I just believe in one fewer god >than you do. When you understand why you dismiss all the other possible >gods, you will understand why I dismiss yours." -- Stephen Roberts
Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Eric Jacobsen wrote:
> > Erik, I like your sig.
:-). Yep, I think this world would be a beter place if if the stupidity or religion was confined to the dustbin of history.
> Minister of Algorithms, Intel Corp.
I still like that title. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ From Time magazine, "Numbers" section: $5 million: Estimated annual cost for a 10-year program that would identify large asteroids most threatening to earth. $75 million: Budget for "Deep Impact", a film about the devastation caused when a comet hits earth.
Hi,
every DSP has libraries as DSPLIB for TMS5xxx optimised for this chip.

Cheers