What to use for deconvolution (library, software, ...)?

DSP, Plug-in and Host development discussion.
soundmodel
KVRian
645 posts since 28 May, 2010 from Finland

Post Mon Jul 17, 2017 3:02 am

What to use for deconvolution (library, software, ...)?

I found a lot of references for Logic's deconvolution program, but I don' t have Logic.

Miles1981
KVRian
1366 posts since 26 Apr, 2004 from UK

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 3:26 am

Deconvolution in what sense, as it seems that you are confusing convolution with what people market as non linear convolution (which means it's not even close to convolution)?

soundmodel
KVRian
645 posts since 28 May, 2010 from Finland

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 3:30 am

To deduce the impulse response from the output.

See, because to construct a filter that models some hardware one must deconvolve the output signal in order to discover the filter that (when applied to the input) created it.

soundmodel
KVRian
645 posts since 28 May, 2010 from Finland

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 4:15 am

Then again, I also think that the deconvolution operation may be simple enough to actually write it oneself, if one has a high-quality FFT implementation already in hand.

https://en.wikipedia.org/wiki/Deconvolution

Unless the division F=H/G can use some meaningful optimization?

Miles1981
KVRian
1366 posts since 26 Apr, 2004 from UK

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 4:47 am

You could do that (which is version 0 of deconvolution), but you end up with division by zeros lots of the time.
You need to accommodate for the noise, the zeros...

soundmodel
KVRian
645 posts since 28 May, 2010 from Finland

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 4:50 am

Miles1981 wrote:You could do that (which is version 0 of deconvolution), but you end up with division by zeros lots of the time.
You need to accommodate for the noise, the zeros...
How ought the zeros be treated? Can I merely replace them with zeros?
Since convolution of Fourier transforms is zero <=> convolution of their derivatives is zero, i.e. at least one of the original contains zero at that point and thus the output would also be a zero at that point?

soundmodel
KVRian
645 posts since 28 May, 2010 from Finland

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 4:56 am


User avatar
nonnaci
KVRist
249 posts since 7 Feb, 2017

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 5:02 am

The IR magnitude spectra shouldn't be flat zero but rather the continuous magnitude spectra is rippling close to zero and on occasion touches zero if the FFT bins happen to align with those frequencies. Maybe raise the noise floor of the IR to compensate.

dmbaer
KVRian
1084 posts since 11 Nov, 2009 from Northern CA

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 11:07 am

So let me ask what may be a very naïve question.

Can you not convolve an impulse signal with a unit impulse (1 followed by as many zeroes as needed to complete the representation) and get back the impulse?

So, for example, if you have a convolver with encrypted impulse signals, you could send the unit impulse into that plug-in and out would come the unencrypted impulse signal. Is that not correct? Seems to me that it should work (at least "in theory" :D ).

soundmodel
KVRian
645 posts since 28 May, 2010 from Finland

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 11:11 am

Edit: nvm
Last edited by soundmodel on Mon Jul 17, 2017 12:39 pm, edited 1 time in total.

matt42
KVRian
1072 posts since 9 Jan, 2006

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 12:33 pm

Wrong

Miles1981
KVRian
1366 posts since 26 Apr, 2004 from UK

Re: What to use for deconvolution (library, software, ...)?

Post Mon Jul 17, 2017 12:36 pm

dmbaer wrote:So let me ask what may be a very naïve question.

Can you not convolve an impulse signal with a unit impulse (1 followed by as many zeroes as needed to complete the representation) and get back the impulse?

So, for example, if you have a convolver with encrypted impulse signals, you could send the unit impulse into that plug-in and out would come the unencrypted impulse signal. Is that not correct? Seems to me that it should work (at least "in theory" :D ).
You can, but you don't get the "best" result. One good way of doing such a thing is to use a Hadamard signal.

dmbaer
KVRian
1084 posts since 11 Nov, 2009 from Northern CA

Re: What to use for deconvolution (library, software, ...)?

Post Tue Jul 18, 2017 3:00 pm

Miles1981 wrote:You can, but you don't get the "best" result. One good way of doing such a thing is to use a Hadamard signal.
Thanks. Looks like it's "google, here I come".

Lorenz @ XARC Mastering
KVRist
116 posts since 20 May, 2003 from Germany

Re: What to use for deconvolution (library, software, ...)?

Post Mon Mar 05, 2018 2:29 pm

A bit late to the party, but http://www.voxengo.com/product/deconvolver/ is what you are looking for.
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