[PD] WG: Inverse bandpass filter

[Alexandre Torres Porres]

could be, I know nothing really about it. But I think I've read something
that stated so. And I also tried it and saw that you could inverse filters
like that.

cheers


2014-04-22 21:06 GMT-03:00 Robert Esler <robert at urbanstew.org>:

> Though with DC  you don't have the issue of phase.  I'm not an expert in
> filter math, but I assume that by the time your filtered audio (assuming
> its not DC) gets subtracted by the [-~] object it is out of phase with the
> original signal.  Moreover, I hear a distinct difference.  Maybe I'm not
> conceiving your statement properly and perhaps this discussion has been
> about DC all along…
>
> Regards
>
>
> From: Alexandre Torres Porres <porres at gmail.com>
> Date: Tuesday, April 22, 2014 3:51 PM
> To: GCC <robert at urbanstew.org>
> Cc: <apvague at gmail.com>, Ingo <ingo at miamiwave.com>, pd-lista puredata <
> pd-list at iem.at>
>
> Subject: Re: [PD] WG: Inverse bandpass filter
>
> can;t remember where I saw about this, but check this link
>
> http://msp.ucsd.edu/techniques/v0.11/book-html/node141.html
>
> see the quote "An easy and practical way to remove the zero-frequency
> component from an audio signal is to use a one-pole low-pass filter to
> extract it, and then subtract the result from the signal. The resulting
> transfer function is one minus the transfer function of the low-pass
> filter:"
>
> doesn't it agree with what I said?
>
>
> cheers
>
>
>
> 2014-04-22 14:37 GMT-03:00 Robert Esler <robert at urbanstew.org>:
>
>> I could be wrong, but I don't think it's quite the same thing.  I believe
>> the signal would be out of phase negating many of the effects of the
>> filter.  I would recommend using [biquad~] and in pd-extended there is a
>> [notch] object which takes care of the coefficients.  This sounds much
>> cleaner and more notch-like to my ear than subtracting the filtered output.
>>
>>  There is an explanation in Miller's book if you like unit circle math:
>> http://msp.ucsd.edu/techniques/latest/book-html/node144.html
>> -----------
>> Message: 4
>> Date: Tue, 22 Apr 2014 01:59:07 -0300
>> From: Alexandre Torres Porres <porres at gmail.com>
>> Subject: Re: [PD] WG: Inverse bandpass filter
>> To: Ingo <ingo at miamiwave.com>
>> Cc: pd-list <pd-list at iem.at>
>> Message-ID:
>> <CAEAsFmhD0HanLmv9vutcSQZjkZY69i7wMeBqQ+20S2riWYaakw at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> isn't it just subtract the audio from the filtered output?
>>
>> I guess you can get inverse freq response just by that
>>
>> cheers
>>
>>
>> 2014-04-18 17:21 GMT-03:00 Ingo <ingo at miamiwave.com>:
>>
>> You could send the original signal in parallel and invert the phase by
>> multiplying with -1. You might have to delay the original signal in case
>> that the processed signal gets also delayed by one or more blocks.
>>
>> Ingo
>>
>> _______________________________________
>> > Von: pd-list-bounces at iem.at [mailto:pd-list-bounces at iem.at<pd-list-bounces at iem.at>]
>> Im Auftrag
>> von
>> > AP Vague
>> > Gesendet: Freitag, 18. April 2014 18:49
>> > An: pd-list at iem.at
>> > Betreff: [PD] Inverse bandpass filter
>> >
>> > Is there a simple way to make [bp~] or [vcf~] have an inverse function?
>> To
>> > filter out, rather than pass a changing frequency value. Is the easiest
>> > way to do this with a combination of [lop~] and [hip~]?
>>
>>
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>
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