tsiry-sandratraina.com
A modern Music Player Daemon based on Rockbox open source high quality audio player
libadwaita
audio
rust
zig
deno
mpris
rockbox
mpd
1/* (C) Guenter Geiger <geiger@epy.co.at> */
2
3
4/*
5
6 These filter coefficients computations are taken from
7 http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
8
9 written by Robert Bristow-Johnson
10
11*/
12
13#ifdef ROCKBOX
14#include "plugin.h"
15#include "../../pdbox.h"
16#include "../src/m_pd.h"
17#include "../../math.h"
18#include "filters.h"
19#else /* ROCKBOX */
20#include "../src/m_pd.h"
21#ifdef NT
22#pragma warning( disable : 4244 )
23#pragma warning( disable : 4305 )
24#endif
25#include <math.h>
26#include "filters.h"
27#endif /* ROCKBOX */
28
29
30/* ------------------- lowpass ----------------------------*/
31
32static t_class *lowpass_class;
33
34void lowpass_bang(t_rbjfilter *x)
35{
36 t_atom at[5];
37 t_float omega = e_omega(x->x_freq,x->x_rate);
38 t_float alpha = e_alpha(x->x_bw*0.01,omega);
39 t_float b1 = 1 - cos(omega);
40 t_float b0 = b1/2.;
41 t_float b2 = b0;
42 t_float a0 = 1 + alpha;
43 t_float a1 = -2.*cos(omega);
44 t_float a2 = 1 - alpha;
45
46/* post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
47
48 if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
49 post("lowpass: filter unstable -> resetting");
50 a0=1.;a1=0.;a2=0.;
51 b0=1.;b1=0.;b2=0.;
52 }
53
54 SETFLOAT(at,-a1/a0);
55 SETFLOAT(at+1,-a2/a0);
56 SETFLOAT(at+2,b0/a0);
57 SETFLOAT(at+3,b1/a0);
58 SETFLOAT(at+4,b2/a0);
59
60 outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
61}
62
63
64void lowpass_float(t_rbjfilter *x,t_floatarg f)
65{
66 x->x_freq = f;
67 lowpass_bang(x);
68}
69
70
71static void *lowpass_new(t_floatarg f,t_floatarg bw)
72{
73 t_rbjfilter *x = (t_rbjfilter *)pd_new(lowpass_class);
74
75 x->x_rate = 44100.0;
76 outlet_new(&x->x_obj,&s_float);
77/* floatinlet_new(&x->x_obj, &x->x_gain); */
78 floatinlet_new(&x->x_obj, &x->x_bw);
79
80 if (f > 0.) x->x_freq = f;
81 if (bw > 0.) x->x_bw = bw;
82 return (x);
83}
84
85
86void lowpass_setup(void)
87{
88 lowpass_class = class_new(gensym("lowpass"), (t_newmethod)lowpass_new, 0,
89 sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,0);
90 class_addbang(lowpass_class,lowpass_bang);
91 class_addfloat(lowpass_class,lowpass_float);
92}
93
94