[PD] PD's biquad (all pole resonant filter)
Hi,
I'm trying to implement in PD a resonant all pole filter, that I used
in max before.
It is using a biquad~ with some adequate coefficients.
So I make a patch reproducing the one in max, with respect to
compatibility with PD, it means that I change it a little so all the
objects used are now common to PD and Max.
And this patch is working in Max correctly. I tested it with Max 4.5,
Mac os 10.5.8 (I don't have Max 5).
the biquad~ is working with lowpass coefficient (using the 'lowpass'
external from ggee) but not with the coefficient that I want to use :-(
I thought that maybe the PD version was not accepting 0 values for the
second and third coefficient of the list so a put 0.01 value
instead of 0 , but it doesn't seem to be this.
I had a look at Miller's code in the d_filter.c file, in [ static void
sigbiquad_list(t_sigbiquad *x, t_symbol *s, int argc, t_atom *argv) ]
t_float discriminant = fb1 * fb1 + 4 * fb2;
t_biquadctl *c = x-x_ctl;
if (discriminant 0) /* imaginary roots -- resonant filter */
{
/* they're conjugates so we just check that the product
is less than one */
if (fb2 = -1.0f) goto stable;
}
else/* real roots */
{...
}
/* if unstable, just bash to zero */
fb1 = fb2 = ff1 = ff2 = ff3 = 0;
and I saw something about a stable criteria 'discriminant' , I wonder
if it is maybe a reason why it is not working with my coefficient.
they are working in Max but not in PD.
if anyone know the answer, it will be very well come, it's still a
mystery for me.
best,
loic
here is my patch:
#N canvas 311 124 720 796 10;
#X msg 256 523 0.0006 1e-06 1e-06 -1.98252 0.994522;
#X msg 343 55 1;
#X obj 343 31 loadbang;
#X msg 184 71 20;
#X obj 182 34 loadbang;
#X msg 25 66 770;
#X obj 25 43 loadbang;
#X msg 398 621 0.000599788 0 0 -2 1;
#X obj 398 598 prepend set;
#X obj 245 657 dac~;
#X obj 249 626 biquad~;
#X obj 111 541 phasor~ 110;
#X msg 448 90 44100;
#X obj 448 65 loadbang;
#X floatatom 381 56 0 0 0 0 - - -;
#X floatatom 239 59 0 0 0 0 - - -;
#X floatatom 120 66 0 0 0 0 - - -;
#X obj 343 77 t b f;
#X obj 205 498 * 1;
#X floatatom 218 273 0 0 0 0 - - -;
#X floatatom 464 374 0 0 0 0 - - -;
#X obj 79 292 expr 1-($f2/(2*$f1));
#X obj 460 337 f;
#X obj 29 435 expr (1-$f1)*sqrt(1-2*$f1*cos(2*$f2)+($f1*$f1));
#X obj 444 116 / 2;
#X obj 78 88 t b f;
#X obj 225 218 / 22050;
#X obj 95 110 * 3.14159;
#X text 96 57 fc;
#X text 196 54 Q;
#X obj 249 565 pack 0.0006 0 0 -1.98252 0.994522;
#X text 557 494 b2;
#X obj 388 458 expr -2*$f1*cos($f2);
#X obj 519 459 expr $f1*$f1;
#X text 61 479 a0;
#X text 395 479 b1;
#X text 316 56 G;
#X connect 0 0 30 0;
#X connect 1 0 17 0;
#X connect 2 0 1 0;
#X connect 3 0 21 0;
#X connect 4 0 3 0;
#X connect 5 0 25 0;
#X connect 6 0 5 0;
#X connect 8 0 7 0;
#X connect 10 0 9 0;
#X connect 10 0 9 1;
#X connect 11 0 10 0;
#X connect 12 0 24 0;
#X connect 13 0 12 0;
#X connect 14 0 17 0;
#X connect 15 0 21 0;
#X connect 16 0 25 0;
#X connect 17 0 21 0;
#X connect 17 0 27 0;
#X connect 17 1 18 1;
#X connect 18 0 30 0;
#X connect 21 0 22 0;
#X connect 22 0 23 0;
#X connect 22 0 32 0;
#X connect 22 0 20 0;
#X connect 22 0 33 0;
#X connect 23 0 18 0;
#X connect 24 0 26 1;
#X connect 25 0 21 0;
#X connect 25 1 27 0;
#X connect 26 0 21 1;
#X connect 26 0 19 0;
#X connect 26 0 23 1;
#X connect 26 0 32 1;
#X connect 27 0 26 0;
#X connect 30 0 10 0;
#X connect 30 0 8 0;
#X connect 32 0 30 3;
#X connect 33 0 30 4;
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Re: [PD] PD's biquad (all pole resonant filter)
hello Loic,
i'm not sure if pd and max biquad are the same structure.
http://en.wikipedia.org/wiki/Digital_biquad_filter
pd use the direct form 2.
i think that max use the form 1 (but may be wrong).
i made a bq~ object that use form 1 (and using audio input for the coef).
maybe it will help.
it is on the nusmuk folder in svn. don't know about pd-extended.
Cyrille
Loic Kessous a écrit :
Hi,
I'm trying to implement in PD a resonant all pole filter, that I used in
max before.
It is using a biquad~ with some adequate coefficients.
So I make a patch reproducing the one in max, with respect to
compatibility with PD, it means that I change it a little so all the
objects used are now common to PD and Max.
And this patch is working in Max correctly. I tested it with Max 4.5,
Mac os 10.5.8 (I don't have Max 5).
the biquad~ is working with lowpass coefficient (using the 'lowpass'
external from ggee) but not with the coefficient that I want to use :-(
I thought that maybe the PD version was not accepting 0 values for the
second and third coefficient of the list so a put 0.01 value instead
of 0 , but it doesn't seem to be this.
I had a look at Miller's code in the d_filter.c file, in [ static void
sigbiquad_list(t_sigbiquad *x, t_symbol *s, int argc, t_atom *argv) ]
t_float discriminant = fb1 * fb1 + 4 * fb2;
t_biquadctl *c = x-x_ctl;
if (discriminant 0) /* imaginary roots -- resonant filter */
{
/* they're conjugates so we just check that the product
is less than one */
if (fb2 = -1.0f) goto stable;
}
else/* real roots */
{...
}
/* if unstable, just bash to zero */
fb1 = fb2 = ff1 = ff2 = ff3 = 0;
and I saw something about a stable criteria 'discriminant' , I wonder if
it is maybe a reason why it is not working with my coefficient. they
are working in Max but not in PD.
if anyone know the answer, it will be very well come, it's still a
mystery for me.
best,
loic
here is my patch:
#N canvas 311 124 720 796 10;
#X msg 256 523 0.0006 1e-06 1e-06 -1.98252 0.994522;
#X msg 343 55 1;
#X obj 343 31 loadbang;
#X msg 184 71 20;
#X obj 182 34 loadbang;
#X msg 25 66 770;
#X obj 25 43 loadbang;
#X msg 398 621 0.000599788 0 0 -2 1;
#X obj 398 598 prepend set;
#X obj 245 657 dac~;
#X obj 249 626 biquad~;
#X obj 111 541 phasor~ 110;
#X msg 448 90 44100;
#X obj 448 65 loadbang;
#X floatatom 381 56 0 0 0 0 - - -;
#X floatatom 239 59 0 0 0 0 - - -;
#X floatatom 120 66 0 0 0 0 - - -;
#X obj 343 77 t b f;
#X obj 205 498 * 1;
#X floatatom 218 273 0 0 0 0 - - -;
#X floatatom 464 374 0 0 0 0 - - -;
#X obj 79 292 expr 1-($f2/(2*$f1));
#X obj 460 337 f;
#X obj 29 435 expr (1-$f1)*sqrt(1-2*$f1*cos(2*$f2)+($f1*$f1));
#X obj 444 116 / 2;
#X obj 78 88 t b f;
#X obj 225 218 / 22050;
#X obj 95 110 * 3.14159;
#X text 96 57 fc;
#X text 196 54 Q;
#X obj 249 565 pack 0.0006 0 0 -1.98252 0.994522;
#X text 557 494 b2;
#X obj 388 458 expr -2*$f1*cos($f2);
#X obj 519 459 expr $f1*$f1;
#X text 61 479 a0;
#X text 395 479 b1;
#X text 316 56 G;
#X connect 0 0 30 0;
#X connect 1 0 17 0;
#X connect 2 0 1 0;
#X connect 3 0 21 0;
#X connect 4 0 3 0;
#X connect 5 0 25 0;
#X connect 6 0 5 0;
#X connect 8 0 7 0;
#X connect 10 0 9 0;
#X connect 10 0 9 1;
#X connect 11 0 10 0;
#X connect 12 0 24 0;
#X connect 13 0 12 0;
#X connect 14 0 17 0;
#X connect 15 0 21 0;
#X connect 16 0 25 0;
#X connect 17 0 21 0;
#X connect 17 0 27 0;
#X connect 17 1 18 1;
#X connect 18 0 30 0;
#X connect 21 0 22 0;
#X connect 22 0 23 0;
#X connect 22 0 32 0;
#X connect 22 0 20 0;
#X connect 22 0 33 0;
#X connect 23 0 18 0;
#X connect 24 0 26 1;
#X connect 25 0 21 0;
#X connect 25 1 27 0;
#X connect 26 0 21 1;
#X connect 26 0 19 0;
#X connect 26 0 23 1;
#X connect 26 0 32 1;
#X connect 27 0 26 0;
#X connect 30 0 10 0;
#X connect 30 0 8 0;
#X connect 32 0 30 3;
#X connect 33 0 30 4;
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Re: [PD] PD's biquad (all pole resonant filter)
Thanks Cyrille, this is a very good thing!
it is also in extended apparently, but I didn't found it for for mac ,
the makefile is there so I tried a make...
but it seems that something is not well configure on the mac on which
I'm working right now(an old ppc), it doesn't recognize the 'make'
command ...hum ^^
even if the dev tools are installed (I'm sure as I compiled some stuff
with xcode some days ago)
let me know if there is already a mac version, if not I also have a
new iMac and I will work on it next week and try to make one.
On 12 sept. 09, at 16:14, cyrille henry wrote:
hello Loic,
i'm not sure if pd and max biquad are the same structure.
http://en.wikipedia.org/wiki/Digital_biquad_filter
pd use the direct form 2.
...so in this case, I suppose there should be a different calculation
for the coefficients,. This could explains why it's not working.
thanks
loic
i think that max use the form 1 (but may be wrong).
i made a bq~ object that use form 1 (and using audio input for the
coef).
maybe it will help.
it is on the nusmuk folder in svn. don't know about pd-extended.
Cyrille
Loic Kessous a écrit :
Hi,
I'm trying to implement in PD a resonant all pole filter, that I
used in max before.
It is using a biquad~ with some adequate coefficients.
So I make a patch reproducing the one in max, with respect to
compatibility with PD, it means that I change it a little so all
the objects used are now common to PD and Max.
And this patch is working in Max correctly. I tested it with Max
4.5, Mac os 10.5.8 (I don't have Max 5).
the biquad~ is working with lowpass coefficient (using the
'lowpass' external from ggee) but not with the coefficient that I
want to use :-(
I thought that maybe the PD version was not accepting 0 values for
the second and third coefficient of the list so a put 0.01
value instead of 0 , but it doesn't seem to be this.
I had a look at Miller's code in the d_filter.c file, in [ static
void sigbiquad_list(t_sigbiquad *x, t_symbol *s, int argc, t_atom
*argv) ]
t_float discriminant = fb1 * fb1 + 4 * fb2;
t_biquadctl *c = x-x_ctl;
if (discriminant 0) /* imaginary roots -- resonant filter */
{
/* they're conjugates so we just check that the product
is less than one */
if (fb2 = -1.0f) goto stable;
}
else/* real roots */
{...
}
/* if unstable, just bash to zero */
fb1 = fb2 = ff1 = ff2 = ff3 = 0;
and I saw something about a stable criteria 'discriminant' , I
wonder if it is maybe a reason why it is not working with my
coefficient. they are working in Max but not in PD.
if anyone know the answer, it will be very well come, it's still a
mystery for me.
best,
loic
here is my patch:
#N canvas 311 124 720 796 10;
#X msg 256 523 0.0006 1e-06 1e-06 -1.98252 0.994522;
#X msg 343 55 1;
#X obj 343 31 loadbang;
#X msg 184 71 20;
#X obj 182 34 loadbang;
#X msg 25 66 770;
#X obj 25 43 loadbang;
#X msg 398 621 0.000599788 0 0 -2 1;
#X obj 398 598 prepend set;
#X obj 245 657 dac~;
#X obj 249 626 biquad~;
#X obj 111 541 phasor~ 110;
#X msg 448 90 44100;
#X obj 448 65 loadbang;
#X floatatom 381 56 0 0 0 0 - - -;
#X floatatom 239 59 0 0 0 0 - - -;
#X floatatom 120 66 0 0 0 0 - - -;
#X obj 343 77 t b f;
#X obj 205 498 * 1;
#X floatatom 218 273 0 0 0 0 - - -;
#X floatatom 464 374 0 0 0 0 - - -;
#X obj 79 292 expr 1-($f2/(2*$f1));
#X obj 460 337 f;
#X obj 29 435 expr (1-$f1)*sqrt(1-2*$f1*cos(2*$f2)+($f1*$f1));
#X obj 444 116 / 2;
#X obj 78 88 t b f;
#X obj 225 218 / 22050;
#X obj 95 110 * 3.14159;
#X text 96 57 fc;
#X text 196 54 Q;
#X obj 249 565 pack 0.0006 0 0 -1.98252 0.994522;
#X text 557 494 b2;
#X obj 388 458 expr -2*$f1*cos($f2);
#X obj 519 459 expr $f1*$f1;
#X text 61 479 a0;
#X text 395 479 b1;
#X text 316 56 G;
#X connect 0 0 30 0;
#X connect 1 0 17 0;
#X connect 2 0 1 0;
#X connect 3 0 21 0;
#X connect 4 0 3 0;
#X connect 5 0 25 0;
#X connect 6 0 5 0;
#X connect 8 0 7 0;
#X connect 10 0 9 0;
#X connect 10 0 9 1;
#X connect 11 0 10 0;
#X connect 12 0 24 0;
#X connect 13 0 12 0;
#X connect 14 0 17 0;
#X connect 15 0 21 0;
#X connect 16 0 25 0;
#X connect 17 0 21 0;
#X connect 17 0 27 0;
#X connect 17 1 18 1;
#X connect 18 0 30 0;
#X connect 21 0 22 0;
#X connect 22 0 23 0;
#X connect 22 0 32 0;
#X connect 22 0 20 0;
#X connect 22 0 33 0;
#X connect 23 0 18 0;
#X connect 24 0 26 1;
#X connect 25 0 21 0;
#X connect 25 1 27 0;
#X connect 26 0 21 1;
#X connect 26 0 19 0;
#X connect 26 0 23 1;
#X connect 26 0 32 1;
#X connect 27 0 26 0;
#X connect 30 0 10 0;
#X connect 30 0 8 0;
#X connect 32 0 30 3;
#X connect 33 0 30 4;
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Re: [PD] PD's biquad (all pole resonant filter)
Loic Kessous a écrit :
Thanks Cyrille, this is a very good thing!
it is also in extended apparently, but I didn't found it for for mac ,
the makefile is there so I tried a make...
but it seems that something is not well configure on the mac on which
I'm working right now(an old ppc), it doesn't recognize the 'make'
command ...hum ^^
even if the dev tools are installed (I'm sure as I compiled some stuff
with xcode some days ago)
let me know if there is already a mac version,
i don't have one, and don't have any ppc computer.
can't help.
Cyrille
if not I also have a new
iMac and I will work on it next week and try to make one.
On 12 sept. 09, at 16:14, cyrille henry wrote:
hello Loic,
i'm not sure if pd and max biquad are the same structure.
http://en.wikipedia.org/wiki/Digital_biquad_filter
pd use the direct form 2.
...so in this case, I suppose there should be a different calculation
for the coefficients,. This could explains why it's not working.
thanks
loic
i think that max use the form 1 (but may be wrong).
i made a bq~ object that use form 1 (and using audio input for the coef).
maybe it will help.
it is on the nusmuk folder in svn. don't know about pd-extended.
Cyrille
Loic Kessous a écrit :
Hi,
I'm trying to implement in PD a resonant all pole filter, that I used
in max before.
It is using a biquad~ with some adequate coefficients.
So I make a patch reproducing the one in max, with respect to
compatibility with PD, it means that I change it a little so all the
objects used are now common to PD and Max.
And this patch is working in Max correctly. I tested it with Max 4.5,
Mac os 10.5.8 (I don't have Max 5).
the biquad~ is working with lowpass coefficient (using the 'lowpass'
external from ggee) but not with the coefficient that I want to use :-(
I thought that maybe the PD version was not accepting 0 values for
the second and third coefficient of the list so a put 0.01 value
instead of 0 , but it doesn't seem to be this.
I had a look at Miller's code in the d_filter.c file, in [ static
void sigbiquad_list(t_sigbiquad *x, t_symbol *s, int argc, t_atom
*argv) ]
t_float discriminant = fb1 * fb1 + 4 * fb2;
t_biquadctl *c = x-x_ctl;
if (discriminant 0) /* imaginary roots -- resonant filter */
{
/* they're conjugates so we just check that the product
is less than one */
if (fb2 = -1.0f) goto stable;
}
else/* real roots */
{...
}
/* if unstable, just bash to zero */
fb1 = fb2 = ff1 = ff2 = ff3 = 0;
and I saw something about a stable criteria 'discriminant' , I wonder
if it is maybe a reason why it is not working with my coefficient.
they are working in Max but not in PD.
if anyone know the answer, it will be very well come, it's still a
mystery for me.
best,
loic
here is my patch:
#N canvas 311 124 720 796 10;
#X msg 256 523 0.0006 1e-06 1e-06 -1.98252 0.994522;
#X msg 343 55 1;
#X obj 343 31 loadbang;
#X msg 184 71 20;
#X obj 182 34 loadbang;
#X msg 25 66 770;
#X obj 25 43 loadbang;
#X msg 398 621 0.000599788 0 0 -2 1;
#X obj 398 598 prepend set;
#X obj 245 657 dac~;
#X obj 249 626 biquad~;
#X obj 111 541 phasor~ 110;
#X msg 448 90 44100;
#X obj 448 65 loadbang;
#X floatatom 381 56 0 0 0 0 - - -;
#X floatatom 239 59 0 0 0 0 - - -;
#X floatatom 120 66 0 0 0 0 - - -;
#X obj 343 77 t b f;
#X obj 205 498 * 1;
#X floatatom 218 273 0 0 0 0 - - -;
#X floatatom 464 374 0 0 0 0 - - -;
#X obj 79 292 expr 1-($f2/(2*$f1));
#X obj 460 337 f;
#X obj 29 435 expr (1-$f1)*sqrt(1-2*$f1*cos(2*$f2)+($f1*$f1));
#X obj 444 116 / 2;
#X obj 78 88 t b f;
#X obj 225 218 / 22050;
#X obj 95 110 * 3.14159;
#X text 96 57 fc;
#X text 196 54 Q;
#X obj 249 565 pack 0.0006 0 0 -1.98252 0.994522;
#X text 557 494 b2;
#X obj 388 458 expr -2*$f1*cos($f2);
#X obj 519 459 expr $f1*$f1;
#X text 61 479 a0;
#X text 395 479 b1;
#X text 316 56 G;
#X connect 0 0 30 0;
#X connect 1 0 17 0;
#X connect 2 0 1 0;
#X connect 3 0 21 0;
#X connect 4 0 3 0;
#X connect 5 0 25 0;
#X connect 6 0 5 0;
#X connect 8 0 7 0;
#X connect 10 0 9 0;
#X connect 10 0 9 1;
#X connect 11 0 10 0;
#X connect 12 0 24 0;
#X connect 13 0 12 0;
#X connect 14 0 17 0;
#X connect 15 0 21 0;
#X connect 16 0 25 0;
#X connect 17 0 21 0;
#X connect 17 0 27 0;
#X connect 17 1 18 1;
#X connect 18 0 30 0;
#X connect 21 0 22 0;
#X connect 22 0 23 0;
#X connect 22 0 32 0;
#X connect 22 0 20 0;
#X connect 22 0 33 0;
#X connect 23 0 18 0;
#X connect 24 0 26 1;
#X connect 25 0 21 0;
#X connect 25 1 27 0;
#X connect 26 0 21 1;
#X connect 26 0 19 0;
#X connect 26 0 23 1;
#X connect 26 0 32 1;
#X connect 27 0 26 0;
#X connect 30 0 10 0;
#X connect 30 0 8 0;
#X connect 32 0 30 3;
#X connect 33 0 30 4;
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