Commit 580b406bafaa695e467493c1423f946295235d11
2020-02-11T14:31:16
Butterworth lowpass fifth order filter
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diff --git a/Makefile.am b/Makefile.am
index 887174c..098b223 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -99,6 +99,7 @@ librtbuf_signal_la_SOURCES = \
rtbuf_signal_lowpass2.c \
rtbuf_signal_lowpass3.c \
rtbuf_signal_lowpass4.c \
+ rtbuf_signal_lowpass5.c \
rtbuf_signal_sinus.c \
rtbuf_signal_square.c \
rtbuf_signal_type.h
diff --git a/rtbuf_signal.c b/rtbuf_signal.c
index 38e46b4..d3150a4 100644
--- a/rtbuf_signal.c
+++ b/rtbuf_signal.c
@@ -167,6 +167,25 @@ s_rtbuf_lib_proc_out g_rtbuf_signal_lowpass4_out[] = {
{ "y4", RTBUF_SIGNAL_SAMPLE_TYPE },
{ 0, 0 } };
+s_rtbuf_lib_proc_in g_rtbuf_signal_lowpass5_in[] = {
+ { "signal", RTBUF_SIGNAL_TYPE, 0.0, -1.0, 1.0 },
+ { "cutoff", RTBUF_SIGNAL_TYPE, 400.0, 0.0, RTBUF_SIGNAL_SAMPLERATE / 2.0 },
+ { 0, 0, 0.0, 0.0, 0.0 } };
+
+s_rtbuf_lib_proc_out g_rtbuf_signal_lowpass5_out[] = {
+ { "signal", RTBUF_SIGNAL_TYPE },
+ { "x1", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "x2", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "x3", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "x4", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "x5", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "y1", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "y2", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "y3", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "y4", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { "y5", RTBUF_SIGNAL_SAMPLE_TYPE },
+ { 0, 0 } };
+
s_rtbuf_lib_proc_in g_rtbuf_signal_sinus_in[] = {
{ "frequency", RTBUF_SIGNAL_TYPE, 220.0, 0.0, RTBUF_SIGNAL_SAMPLERATE / 2.0 },
{ "amplitude", RTBUF_SIGNAL_TYPE, 1.0, 0.0, 1.0 },
@@ -211,6 +230,8 @@ s_rtbuf_lib_proc rtbuf_lib_proc[] = {
g_rtbuf_signal_lowpass3_in, g_rtbuf_signal_lowpass3_out },
{ "lowpass4", rtbuf_signal_lowpass4, rtbuf_signal_lowpass4_start, 0,
g_rtbuf_signal_lowpass4_in, g_rtbuf_signal_lowpass4_out },
+ { "lowpass5", rtbuf_signal_lowpass5, rtbuf_signal_lowpass5_start, 0,
+ g_rtbuf_signal_lowpass5_in, g_rtbuf_signal_lowpass5_out },
{ "sinus", rtbuf_signal_sinus, rtbuf_signal_sinus_start, 0,
g_rtbuf_signal_sinus_in, g_rtbuf_signal_sinus_out },
{ "square", rtbuf_signal_square, rtbuf_signal_square_start, 0,
diff --git a/rtbuf_signal.h b/rtbuf_signal.h
index 5311bd4..cbafec5 100644
--- a/rtbuf_signal.h
+++ b/rtbuf_signal.h
@@ -251,6 +251,27 @@ typedef struct rtbuf_signal_lowpass4_data {
int rtbuf_signal_lowpass4 (s_rtbuf *rtb);
int rtbuf_signal_lowpass4_start (s_rtbuf *rtb);
+/* butterworth lowpass filter, fifth order */
+
+#pragma pack(push,1)
+typedef struct rtbuf_signal_lowpass5_data {
+ t_rtbuf_signal signal;
+ t_rtbuf_signal_sample x1;
+ t_rtbuf_signal_sample x2;
+ t_rtbuf_signal_sample x3;
+ t_rtbuf_signal_sample x4;
+ t_rtbuf_signal_sample x5;
+ t_rtbuf_signal_sample y1;
+ t_rtbuf_signal_sample y2;
+ t_rtbuf_signal_sample y3;
+ t_rtbuf_signal_sample y4;
+ t_rtbuf_signal_sample y5;
+} s_rtbuf_signal_lowpass5_data;
+#pragma pack(pop)
+
+int rtbuf_signal_lowpass5 (s_rtbuf *rtb);
+int rtbuf_signal_lowpass5_start (s_rtbuf *rtb);
+
/* sinus */
#pragma pack(push,1)
diff --git a/rtbuf_signal_lowpass5.c b/rtbuf_signal_lowpass5.c
new file mode 100644
index 0000000..61f80ec
--- /dev/null
+++ b/rtbuf_signal_lowpass5.c
@@ -0,0 +1,147 @@
+/*
+ * Copyright 2020 Thomas de Grivel <thoxdg@gmail.com> +33614550127
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* Butterworth lowpass fourth order filter
+a: (sqrt(5)-1)/2 $
+b: (sqrt(5)+1)/2 $
+s: 2*F*(1-z)/(1+z) $
+B5:(s/w+1)*((s/w)^2+a*(s/w)+1)*((s/w)^2+b*s/w+1) $
+H: 1/B5 $
+ratsimp(H);
+ 5 5 5 4 5 3 5 2 5 5
+(w z + 5 w z + 10 w z + 10 w z + 5 w z + w )
+ 5 4 2 3
+/((w + ((- 2 sqrt(5)) - 2) F w + (4 sqrt(5) + 12) F w
+ 3 2 4 5 5
+ + ((- 8 sqrt(5)) - 24) F w + (16 sqrt(5) + 16) F w - 32 F ) z
+ 5 4 2 3
+ + (5 w + ((- 6 sqrt(5)) - 6) F w + (4 sqrt(5) + 12) F w
+ 3 2 4 5 4
+ + (8 sqrt(5) + 24) F w + ((- 48 sqrt(5)) - 48) F w + 160 F ) z
+ 5 4 2 3
+ + (10 w + ((- 4 sqrt(5)) - 4) F w + ((- 8 sqrt(5)) - 24) F w
+ 3 2 4 5 3
+ + (16 sqrt(5) + 48) F w + (32 sqrt(5) + 32) F w - 320 F ) z
+ 5 4 2 3
+ + (10 w + (4 sqrt(5) + 4) F w + ((- 8 sqrt(5)) - 24) F w
+ 3 2 4 5 2
+ + ((- 16 sqrt(5)) - 48) F w + (32 sqrt(5) + 32) F w + 320 F ) z
+ 5 4 2 3
+ + (5 w + (6 sqrt(5) + 6) F w + (4 sqrt(5) + 12) F w
+ 3 2 4 5
+ + ((- 8 sqrt(5)) - 24) F w + ((- 48 sqrt(5)) - 48) F w - 160 F ) z
+ 5 4 2 3
+ + w + (2 sqrt(5) + 2) F w + (4 sqrt(5) + 12) F w
+ 3 2 4 5
+ + (8 sqrt(5) + 24) F w + (16 sqrt(5) + 16) F w + 32 F )
+
+a: w5 + (r5 + 1)( 2)(f w4 + 8 f4 w) + (4 r5 + 12) (f2 w3 + 2 f3 w2) + 32 f5; z
+b: 5 w5 + (r5 + 1)( 6)(f w4 - 8 f4 w) + (4 r5 + 12) (f2 w3 - 2 f3 w2) - 160 f5; z1
+c: 10 w5 + (r5 + 1)( 4)(f w4 + 8 f4 w) + (4 r5 + 12)(-2)(f2 w3 + 2 f3 w2) + 320 f5; z2
+d: 10 w5 + (r5 + 1)(-4)(f w4 - 8 f4 w) + (4 r5 + 12)(-2)(f2 w3 - 2 f3 w2) - 320 f5; z3
+e: 5 w5 + (r5 + 1)(-6)(f w4 + 8 f4 w) + (4 r5 + 12) (f2 w3 + 2 f3 w2) + 160 f5; z4
+f: w5 + (r5 + 1)(-2)(f w4 - 8 f4 w) + (4 r5 + 12) (f2 w3 - 2 f3 w2) - 32 f5; z5
+
+*/
+#include <math.h>
+#include "rtbuf.h"
+#include "rtbuf_signal.h"
+
+int rtbuf_signal_lowpass5_start (s_rtbuf *rtb)
+{
+ s_rtbuf_signal_lowpass5_data *data;
+ assert(rtb->proc->out_bytes == sizeof(*data));
+ data = (s_rtbuf_signal_lowpass5_data*) rtb->data;
+ data->x1 = 0.0;
+ data->x2 = 0.0;
+ data->x3 = 0.0;
+ data->x4 = 0.0;
+ data->x5 = 0.0;
+ data->y1 = 0.0;
+ data->y2 = 0.0;
+ data->y3 = 0.0;
+ data->y4 = 0.0;
+ data->y5 = 0.0;
+ return 0;
+}
+
+int rtbuf_signal_lowpass5 (s_rtbuf *rtb)
+{
+ s_rtbuf_signal_fun in;
+ s_rtbuf_signal_fun cutoff;
+ s_rtbuf_signal_lowpass5_data *data;
+ unsigned int i = 0;
+ const double r5_1 = sqrt(5.0) + 1.0;
+ const double _4r5_12 = 4.0 * sqrt(5.0) + 12.0;
+ const double f = RTBUF_SIGNAL_SAMPLERATE;
+ const double f2 = f * f;
+ const double f3 = f2 * f;
+ const double f4 = f2 * f2;
+ const double f5 = f2 * f3;
+ const double _32f5 = 32.0 * f5;
+ const double _160f5 = 160.0 * f5;
+ const double _320f5 = 320.0 * f5;
+ rtbuf_signal_fun(rtb, RTBUF_SIGNAL_LOWPASS_IN_SIGNAL, &in);
+ rtbuf_signal_fun(rtb, RTBUF_SIGNAL_LOWPASS_IN_CUTOFF, &cutoff);
+ data = (s_rtbuf_signal_lowpass5_data*) rtb->data;
+ while (i < RTBUF_SIGNAL_SAMPLES) {
+ const double x = in.sample_fun(in.signal, i);
+ const double fc = cutoff.sample_fun(cutoff.signal, i);
+ const double w = 2.0 * M_PI * fc;
+ const double _8f4w = 8.0 * f4 * w;
+ const double w2 = w * w;
+ const double _2f3w2 = 2.0 * f3 * w2;
+ const double w3 = w2 * w;
+ const double f2w3 = f2 * w3;
+ const double f2w3p2f3w2 = f2w3 + _2f3w2;
+ const double f2w3m2f3w2 = f2w3 - _2f3w2;
+ const double w4 = w2 * w2;
+ const double fw4 = f * w4;
+ const double fw4p8f4w = (fw4 + _8f4w);
+ const double fw4m8f4w = (fw4 - _8f4w);
+ const double w5 = w2 * w3;
+ const double _5w5 = 5.0 * w5;
+ const double _10w5 = 10.0 * w5;
+ const double a = w5 + r5_1 * 2.0 * fw4p8f4w + _4r5_12 * f2w3p2f3w2 + _32f5;
+ const double b = _5w5 + r5_1 * 6.0 * fw4m8f4w + _4r5_12 * f2w3m2f3w2 - _160f5;
+ const double c = _10w5 + r5_1 * 4.0 * fw4p8f4w + _4r5_12 * -2.0 * f2w3p2f3w2 + _320f5;
+ const double d = _10w5 + r5_1 * -4.0 * fw4m8f4w + _4r5_12 * -2.0 * f2w3m2f3w2 - _320f5;
+ const double e = _5w5 + r5_1 * -6.0 * fw4p8f4w + _4r5_12 * f2w3p2f3w2 + _160f5;
+ const double f = w5 + r5_1 * -2.0 * fw4m8f4w + _4r5_12 * f2w3m2f3w2 - _32f5;
+ data->signal[i] = (w5 * (x
+ + 5.0 * (data->x1
+ + data->x4)
+ + 10.0 * (data->x2
+ + data->x3)
+ + data->x5)
+ - (b * data->y1
+ + c * data->y2
+ + d * data->y3
+ + e * data->y4
+ + f * data->y5)) / a;
+ data->x5 = data->x4;
+ data->x4 = data->x3;
+ data->x3 = data->x2;
+ data->x2 = data->x1;
+ data->x1 = x;
+ data->y5 = data->y4;
+ data->y4 = data->y3;
+ data->y3 = data->y2;
+ data->y2 = data->y1;
+ data->y1 = data->signal[i];
+ i++;
+ }
+ return 0;
+}
diff --git a/test_synth b/test_synth
index 2c5a658..2c1c539 100644
--- a/test_synth
+++ b/test_synth
@@ -18,7 +18,7 @@ bind Synth00 signal Delay00 signal
set Flanger00 = new signal flanger
bind Delay00 signal Flanger00 signal
-set LP00 = new signal lowpass4
+set LP00 = new signal lowpass5
bind Flanger00 signal LP00 signal
set Limiter00 = new dynamic limiter