Sorry I checked your patch again.  I get the same behavior.  I had an older version of Pd I was using.

Yes, I just noticed this too.  It appears OOURA limits the calculation to a block size of 32 or higher.  Why?  The code is so horribly documented I’d rather not even try to figure it out.  

Pd also has the option of using the FFTW3 library by Thomas Grill, which on a surface reading doesn’t seem to have a block boundary.  But I can’t be sure w/o trying it.  Of course this would require a manual compiling of Pd.

Not sure why the mayer fft lib was removed, but this is one of the few instances of Pd breaking older patches.  Maybe this needs to be a dev request?  At the very least print an error to the Pd window.  

-Rob

P.S - I have a C++ version of the old mayer_fft that I could probably wrap into a Pd object if it seems like this is a big enough problem.

On Oct 16, 2015, at 4:09 PM, Matt Barber <brbrofsvl@gmail.com> wrote:

OK, looking at the OOURA code, the init routine has this:

========================

static int ooura_init( int n)

{

    n = (1 << ilog2(n));

    if (n < 64)

        return (0);

========================

then later in the fft/ifft routine:

========================

     if (!ooura_init(2*n))

        return;

========================

and rfft:

========================

    if (!ooura_init(n))

        return;

========================

since these operate directly on samples in the signal vector, it will pass signals in small blocks without performing dft. I don't know what this is supposed to avoid. I've used fft in small block sizes before, and I can't be the only one whose patches might be broken by this.

On Fri, Oct 16, 2015 at 5:33 PM, katja <katjavetter@gmail.com> wrote:

If I understand the fft files correctly OOURA is now the default, but
'disguised' as mayer fft so the old API should remain valid.
(http://sourceforge.net/p/pure-data/pure-data/ci/master/tree/src/d_fft_fftsg.c).

Indeed I get the same result for Matt's test patch with Pd 0.46-5
which is on my system. Sinusoids for block size 8 and 16, instead of
spectrum points.

A while ago I've been reading in OOURA fft code and what I remember
is, Pd uses its mixed radix functions. Not sure about it though.

Katja

On Fri, Oct 16, 2015 at 10:00 PM, Robert Esler <robert@urbanstew.org> wrote:
>
>   As far as I know Pd stopped using the mayer fft library in .46, which is probably why this is new behavior.  I only get what you’re experiencing with a block size of 8.  Otherwise, it seems to perform as expected.
>   To really understand if this is a bug or not is to know which fft library is being used for OS X.   My guess is it’s the OOURA but it’s not clear from looking at [fft~] object code that comes with distribution.
>   You could also download the old library and recompile Pd, but I doubt it’s worth it.
> -Rob
> -------
> Hi list,
>
> There's either a major bug in the [fft~] objects in Pd-0.46.7 (64bit OSX)
> or I'm going crazy. I'd love to see if others can reproduce it.
>
> Basically, for [block~] sizes less than 32 bits, [fft~] doesn't perform --
> it just passes the signal through unchanged. [ifft~] does the same. The
> [rfft~]-[rifft~] is a little more complicated -- it passes signal through
> but zeroes out the last N/2 for [block~] sizes less than 64.
>
>
> See the attached patch, which only shows [fft~]. The saved contents of the
> tables on opening are the results for [block~ 8] on my machine, for
> quarter-nyquist at 44100.
>
> I've never seen this before in other versions of Pd. Anyone else get this
> behavior?
>
> Matt

> _______________________________________________
> Pd-list@lists.iem.at mailing list
> UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list