Re: [yoshimi-user] data types & fft thoughts

[jy <jy...@gm...>]

Hi Cal

Well I'm not sure this could be an issue for a feast reasons :
1 - both double and float types have enough resolution to describe fourier
coefficients for our tasks, meaning that switching these from double to
float might lead to a detuning but it would be so small that we probably
wouldn't be able to hear it. For yoshimi, I guess a precision to the third
to fifth decimal is sufficient.
2 - if switching from double to float lead to such huge differences, this
would be a major issue for libfft, imho. And there could indeed be a bug in
libfft. Unlikely...
3 - last but not least, unless there's a build flag I missed somewhere
allowing to forbid the use of floats for these operations, we would all be
affected.

But hey, I can be wrong!

Le 30 janv. 2011 01:40, "cal" <ca...@gr...> a écrit :
> I still don't claim to understand anything much about fast fourier
transforms,
> but this thought keeps coming to mind. In original zyn and yoshi 0.058.1,
the
> basic buffer data type for the fft processing was double. Beyond 0.058.1,
I
> switched to using the fftwf_ function variants, which are float based
instead
> of double. Both original zyn and yoshi 0.058.1 do _not_ suffer the pitch
> weirdness. With no sound theoretical basic that I understand, maybe it'd
be
> worth trying a revert to doubles through the fft processing?
>
> That's easy enough for me to put together, but I'd like to hear thoughts
on
> whether some kind of weirdness through the transforms might actually
result in
> the problem we're addressing.
>
> cheers, Cal
>
>
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