oh sure, but that's more like a slew or glide and you don't go down to zero anyway :)
and if you're filtering audio, you don't want to keep inaudible stuff. All I'm saying is that if you are soing this to fade to slience you need a DC filter
Em sex., 12 de abr. de 2024 às 04:12, cyrille henry ch@chnry.net escreveu:
I don't think it's weird for a lowpass filter to go under 20Hz. They are not restricted to audio signals. I use them a lot to smooth control signals, or to replace line~. (I really hate line~ to control sound amplitude or preset transition, it's way too robotic)
cheers c
Le 12/04/2024 à 08:01, Alexandre Torres Porres a écrit :
and you got a strong DC component over there :)
anyway, it also seems weird to have a lowpass or a bandpass going as low
as in the 20hz range. If you wanna do it just so it fades out to silence, you need a DC filter, something like a [hip~ 5] object, so when the lowpass, bandpass gets there, then you have nothing.
cheers
Em qui., 11 de abr. de 2024 às 15:40, Antoine Rousseau <
antoine@metalu.net mailto:antoine@metalu.net> escreveu:
Well, let's simplify a bit, forget all the filter complexity (Q,slope, definition of the cutoff frequency...).
Let's just say that the output of a lowpass filter cannot movefaster than the cutoff frequency: a 1Hz filter output cannot move faster than 1Hz (so it can't go back and forth in less than a second or so), a 1kHz can't go back and forth in less than about 1ms, etc. The output of a 0Hz filter can't move... at all. When you set the cutoff to 0Hz, the output freezes to its current value. It won't magically decay to 0.
Hey, if you set the framerate of a movie to 0 frame/second, it willjust stop, and will show the same image forever; it won't fade to black!
Antoine Le jeu. 11 avr. 2024 à 14:08, Peter P. <peterparker@fastmail.commailto:peterparker@fastmail.com> a écrit :
* Antoine Rousseau <antoine@metalu.net <mailto:antoine@metalu.net>> [2024-04-11 13:40]:
> That doesn't seem incorrect to me; after all, a lowpassfilter at 0Hz
> implies that its output is constant (any change would involvefrequencies >
> 0Hz). Thanks Antoine, Why does a lowpass filter, that has a cutoff frequency of 0Hzimply that
it's output is constant? I will describe the problem again hoping that I will understandit
better myseld: I have an oscillating input signal that has some DC offset(unipolar
sawtooth from phasor~). I fade this signal's amplitude to -infdB using
[line~]. I also fade down the filter cutoff (defined as the -3dB point ofthe
filter curve) from 400Hz to 0Hz. The filter will then continueto produce an
non-decaying output. If I fade down the filter cutoff down to only 1Hz, it's outputwill decay (somehow
counterintuitively to me). This is the part I don't get. I understand that vcf~ is a resonant filter, and it can have again
greater 1 around the cutoff frequency, especially for high Qvalues. The
above behavior can also be observed for Q=1. Thanks for all hints! Peter _______________________________________________ Pd-list@lists.iem.at <mailto:Pd-list@lists.iem.at> mailing list UNSUBSCRIBE and account-management ->https://lists.puredata.info/listinfo/pd-list < https://lists.puredata.info/listinfo/pd-list%3E
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