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soundmodel
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492 posts since 28 May, 2010, from Finland

Postby soundmodel; Mon Jul 17, 2017 3:02 am What to use for deconvolution (library, software, ...)?

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
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1254 posts since 26 Apr, 2004, from UK

Postby Miles1981; Mon Jul 17, 2017 3:26 am Re: What to use for deconvolution (library, software, ...)?

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
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492 posts since 28 May, 2010, from Finland

Postby soundmodel; Mon Jul 17, 2017 3:30 am Re: What to use for deconvolution (library, software, ...)?

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
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492 posts since 28 May, 2010, from Finland

Postby soundmodel; Mon Jul 17, 2017 4:15 am Re: What to use for deconvolution (library, software, ...)?

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
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1254 posts since 26 Apr, 2004, from UK

Postby Miles1981; Mon Jul 17, 2017 4:47 am Re: What to use for deconvolution (library, software, ...)?

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
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492 posts since 28 May, 2010, from Finland

Postby soundmodel; Mon Jul 17, 2017 4:50 am Re: What to use for deconvolution (library, software, ...)?

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?
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nonnaci
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201 posts since 7 Feb, 2017

Postby nonnaci; Mon Jul 17, 2017 5:02 am Re: What to use for deconvolution (library, software, ...)?

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
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792 posts since 11 Nov, 2009, from Northern CA

Postby dmbaer; Mon Jul 17, 2017 11:07 am Re: What to use for deconvolution (library, software, ...)?

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
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492 posts since 28 May, 2010, from Finland

Postby soundmodel; Mon Jul 17, 2017 11:11 am Re: What to use for deconvolution (library, software, ...)?

Edit: nvm
Last edited by soundmodel on Mon Jul 17, 2017 12:39 pm, edited 1 time in total.
matt42
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919 posts since 9 Jan, 2006

Postby matt42; Mon Jul 17, 2017 12:33 pm Re: What to use for deconvolution (library, software, ...)?

Wrong
Miles1981
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1254 posts since 26 Apr, 2004, from UK

Postby Miles1981; Mon Jul 17, 2017 12:36 pm Re: What to use for deconvolution (library, software, ...)?

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
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792 posts since 11 Nov, 2009, from Northern CA

Postby dmbaer; Tue Jul 18, 2017 3:00 pm Re: What to use for deconvolution (library, software, ...)?

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".

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