[PD] Filters...

Derek Holzer derek at umatic.nl
Mon Apr 12 23:19:51 CEST 2010

Sorry, the only solutions I've ever known is to antialias the signal 
sources by low-pass filtering them before they reach a sampling rate 
where they could alias, or by using band-limited signal sources in some 
way or another. Once the aliased frequencies are in, it's pretty near 
impossible to get them out.


On 4/12/10 11:10 PM, brandt at subnet.at wrote:
> dear derek, dear list
> is there any possiblity to make an antialaising for the dac output of a
> mixed signal?
> thanks in advance
> der.brandt
> Zitat von "Derek Holzer" <derek at umatic.nl>:
>> The frequency components introduced by aliasing cannot be removed (at
>> least not by low-pass filtering) once introduced, and this happens at
>> the level of signal generation, not at the interface to the dac. Since
>> it is the phasor which is actually aliasing, it needs to be
>> antialiased with a low pass filter before it continues on the a lower
>> sampling rate. So the signal source and the filter need to be in the
>> same upsampled subpatch.
>> Best!
>> D.
>> On 4/12/10 5:49 PM, Pierre Massat wrote:
>>> Hi all,
>>> recently there was a discussion about the different ways of avoiding
>>> aliasing. One of these is oversampling, but as far as i know there is
>>> only one example of it in Pd help patches, and it has a phasor in the
>>> subpatch. I m assuming that i could use the Butterworth filter in the
>>> subpatch without the phasor, am i right? In this case would it make
>>> sense to use it everytime i need i low-pass filter?
>>> This is probably a very silly question...
>> =
>> --
>> ::: derek holzer ::: http://macumbista.net :::
>> ---Oblique Strategy # 45:
>> "Disciplined self-indulgence"
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::: derek holzer ::: http://macumbista.net :::
---Oblique Strategy # 60:
"Don't be afraid of things because they're easy to do"

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