Hi,
I’m looking closer at this strange behavior of ba.selectn().
I’d really like to know if this is expected behavior,
because it looks like a bug to me. (I’m seeing this in
FaustLive version 2.5.17, as installed by MacPorts.)
Basically, if I have N inputs to selectn(), and I use a
hslider with N possible values to select one of those inputs,
the chosen input is not selected. What happens instead
is hard to characterize. This code demonstrates the problem:
import("stdfaust.lib");
N=8;
process = par(i, N, (i : hbargraph("[%2i]val %i", 0, N)))
: ba.selectn(N, hslider("selector", 0, 0, N-1, 1) )
: hbargraph("selected val", 0, N)
;
Interestingly, if I use a hslider with N+1 possible values,
everything seems to work as I’d expect. So that’s a workaround,
although it requires the slider to have one meaningless value.
Can anyone else confirm this? Is this expected behavior?
Or maybe I’m running a bad version of FaustLive? Or I’m
missing some other obvious thing?
Much thanks,
-mykle-
> On Feb 27, 2018, at 4:36 AM, faudiostream-users-requ...@lists.sourceforge.net
> wrote:
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> Today's Topics:
>
> 1. Re: compiler hangs on this program? (Mykle Hansen)
> 2. Re: FAUST Compiler for GPGPU? (l...@grame.fr)
>
> From: Mykle Hansen <my...@mykle.com>
> Subject: Re: [Faudiostream-users] compiler hangs on this program?
> Date: February 26, 2018 at 3:59:32 PM PST
> To: Julius Smith <j...@ccrma.stanford.edu>
> Cc: Oleg Nesterov <o...@redhat.com>, faudiostream-users
> <faudiostream-users@lists.sourceforge.net>
>
>
>> On Feb 23, 2018, at 12:17 PM, Julius Smith <j...@ccrma.stanford.edu> wrote:
>>
>> Hi Mykle,
>>
>> Yes, iFFT takes spectral-bin signals in parallel. Right now they all
>> run at the full audio sampling rate, but later we should be able to
>> downsample as is typical.
>
> Thanks. Clearly I have wandered in over my head, math-wise.
> But after reading all weekend, I think I now (sort of) understand
> the difference between the real and the complex FFT. Or so I’d like
> to prove to myself, by making this algorithm work in Faust. =)
>
> Nevertheless, I’m still struggling. I expect this to work, and it doesn’t:
>
> import("stdfaust.lib”);
> process = no.noise : an.rtocv(N) : an.fft(N) : par(f, N, (/(denom(f)^beta), _
> )) : an.ifft(N) : ba.selectn(N*2, 0)
> with {
> N=8;
> hN = N/2;
> beta = hslider("beta", 1, 0, 3, 0.01);
> // Convert par() index to appropriate coefficient for pos & neg freqs
> produced by complex fft
> // For instance: 0 1 2 3 4 5 6 7 -> 4 3 2 1 1 2 3 4
> denom(f) = ba.if(f < hN, hN-f, f+1 - hN);
> };
>
>
> And while trying to debug that myself, I hit an even bigger snag
> with selectn(). The code below seems pretty straightforward,
> but it does not work at all like I expect, and I haven’t a clue why not:
>
>
> import("stdfaust.lib");
> process = par(i, N, (2*i, 2*i+1)) : par(i, 16, hbargraph("[%2i]value %i", 0,
> 20))
> : ba.selectn(16, pick) : hbargraph("selected value", 0, 20)
> with {
> N=8;
> pick = hslider(“pick a value", 0, 0, 15, 1);
> };
>
>
> (Possibly this is because selectn() expects an integer?
> The SVG shows me that the hslider is producing floats,
> even though there’s not a decimal point in this program.)
>
>> Note that for 1/f noise there is a spectral_tilt function in
>> filters.lib that will provide a 1/f filter for white noise as a
>> special case. More generally it can provide 1/f^alpha over the entire
>> audio band, for any alpha, to any desired degree of accuracy.
>> Moreover, alpha can be safely modulated over time as that only moves
>> the zeros of the filter.
>
> Thank you! For any sort of practical use, I’m sure that would be ideal.
> At the moment I’m just researching the various different approaches to
> synthesizing 1/f noise. I expect this one to be the slowest.
> I wanted to see if I could code in Faust, as a learning exercise.
> (Boy, am I learning …)
>
> -mykle-
>
>
>
>
>
>
>
> From: l...@grame.fr
> Subject: Re: [Faudiostream-users] FAUST Compiler for GPGPU?
> Date: February 27, 2018 at 12:35:59 AM PST
> To: Christoph Kuhr <christoph.k...@web.de>
> Cc: faudiostream-users@lists.sourceforge.net, Thomas Hofmann
> <thomas.hofm...@hs-anhalt.de>
>
>
>
>> Le 27 févr. 2018 à 09:13, Christoph Kuhr <christoph.k...@web.de> a écrit :
>>
>> Hey,
>>
>> we are trying to implement FAUST in our online environment untill CfP.
>> Chances are good that we could submit some proof of concept.
>
> That would be great yes ! Is your « online environment » visible somewhere?
>
>> So, we will try to attend the IFC18. Even if it does not work out, I may be
>> able to drop by.
>>
>> However, I will be present at the LAC 2018.
>>
>>
>> BR,
>> Ck
>>
>
> OK.
>
> Stéphane
>
>
>
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