Add libraries from Osmocom-Analog

5 files changed, 447 insertions, 0 deletions

diff --git a/src/libfilter/Makefile.am b/src/libfilter/Makefile.am
new file mode 100644
index 0000000..45d2ec2
--- /dev/null
+++ b/src/libfilter/Makefile.am
@@ -0,0 +1,8 @@
+AM_CPPFLAGS = -Wall -Wextra -g $(all_includes)
+
+noinst_LIBRARIES = libfilter.a
+
+libfilter_a_SOURCES = \
+	iir_filter.c \
+	fir_filter.c
+
diff --git a/src/libfilter/fir_filter.c b/src/libfilter/fir_filter.c
new file mode 100644
index 0000000..5df4f40
--- /dev/null
+++ b/src/libfilter/fir_filter.c
@@ -0,0 +1,197 @@
+/* FIR filter
+ *
+ * (C) 2017 by Andreas Eversberg <jolly@eversberg.eu>
+ * All Rights Reserved
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include <math.h>
+#include "../libsample/sample.h"
+#include "fir_filter.h"
+
+//#define DEBUG_TAPS
+
+static void kernel(double *taps, int M, double cutoff, int invert)
+{
+	int i;
+	double sum;
+
+	for (i = 0; i <= M; i++) {
+		/* gen sinc */
+		if (i == M / 2)
+			taps[i] = 2.0 * M_PI * cutoff;
+		else
+			taps[i] = sin(2.0 * M_PI * cutoff * (double)(i - M / 2))
+				/ (double)(i - M / 2);
+		/* blackman window */
+		taps[i] *= 0.42 - 0.50 * cos(2 * M_PI * (double)(i / M))
+				+ 0.08 * cos(4 * M_PI * (double)(i / M));
+	}
+
+	/* normalize */
+	sum = 0;
+	for (i = 0; i <= M; i++)
+		sum += taps[i];
+	for (i = 0; i <= M; i++)
+		taps[i] /= sum;
+
+	/* invert */
+	if (invert) {
+		for (i = 0; i <= M; i++)
+			taps[i] = -taps[i];
+		taps[M / 2] += 1.0;
+	}
+
+#ifdef DEBUG_TAPS
+	puts("start");
+	for (i = 0; i <= M; i++)
+		puts(debug_amplitude(taps[i]));
+#endif
+}
+
+static fir_filter_t *fir_init(double samplerate, double transition_bandwidth)
+{
+	fir_filter_t *fir;
+	int M;
+
+	/* alloc struct */
+	fir = calloc(1, sizeof(*fir));
+	if (!fir) {
+		fprintf(stderr, "No memory creating FIR filter!\n");
+		return NULL;
+	}
+
+	/* transition bandwidth */
+	M = ceil(1.0 / (transition_bandwidth / samplerate));
+	if ((M & 1))
+		M++;
+
+//	printf("cutoff=%.4f\n", cutoff / samplerate);
+//	printf("tb=%.4f\n", transition_bandwidth / samplerate);
+	fir->ntaps = M + 1;
+	fir->delay = M / 2;
+
+	/* alloc taps */
+	fir->taps = calloc(fir->ntaps, sizeof(*fir->taps));
+	if (!fir->taps) {
+		fprintf(stderr, "No memory creating FIR filter!\n");
+		fir_exit(fir);
+		return NULL;
+	}
+
+	/* alloc ring buffer */
+	fir->buffer = calloc(fir->ntaps, sizeof(*fir->buffer));
+	if (!fir->buffer) {
+		fprintf(stderr, "No memory creating FIR filter!\n");
+		fir_exit(fir);
+		return NULL;
+	}
+
+
+	return fir;
+}
+
+fir_filter_t *fir_lowpass_init(double samplerate, double cutoff, double transition_bandwidth)
+{
+	/* calculate kernel */
+	fir_filter_t *fir =  fir_init(samplerate, transition_bandwidth);
+	if (!fir)
+		return NULL;
+	kernel(fir->taps, fir->ntaps - 1, cutoff / samplerate, 0);
+	return fir;
+}
+
+fir_filter_t *fir_highpass_init(double samplerate, double cutoff, double transition_bandwidth)
+{
+	fir_filter_t *fir =  fir_init(samplerate, transition_bandwidth);
+	if (!fir)
+		return NULL;
+	kernel(fir->taps, fir->ntaps - 1, cutoff / samplerate, 1);
+	return fir;
+}
+
+fir_filter_t *fir_allpass_init(double samplerate, double transition_bandwidth)
+{
+	fir_filter_t *fir =  fir_init(samplerate, transition_bandwidth);
+	if (!fir)
+		return NULL;
+	fir->taps[(fir->ntaps - 1) / 2] = 1.0;
+	return fir;
+}
+
+fir_filter_t *fir_twopass_init(double samplerate, double cutoff_low, double cutoff_high, double transition_bandwidth)
+{
+	int i;
+	double sum;
+	fir_filter_t *fir =  fir_init(samplerate, transition_bandwidth);
+	if (!fir)
+		return NULL;
+	double lp_taps[fir->ntaps], hp_taps[fir->ntaps];
+	kernel(lp_taps, fir->ntaps - 1, cutoff_low / samplerate, 0);
+	kernel(hp_taps, fir->ntaps - 1, cutoff_high / samplerate, 1);
+	sum = 0;
+	printf("#warning does not work as expected\n");
+	abort();
+	for (i = 0; i < fir->ntaps; i++) {
+		fir->taps[i] = lp_taps[i] + hp_taps[i];
+		sum += fir->taps[i];
+	}
+	/* hp will die */
+//	for (i = 0; i < fir->ntaps; i++)
+	//	fir->taps[i] /= sum;
+	return fir;
+}
+
+void fir_exit(fir_filter_t *fir)
+{
+	if (!fir)
+		return;
+	free(fir->taps);
+	free(fir->buffer);
+	free(fir);
+}
+
+void fir_process(fir_filter_t *fir, sample_t *samples, int num)
+{
+	int i, j;
+	double y;
+
+	for (i = 0; i < num; i++) {
+		/* put sample in ring buffer */
+		fir->buffer[fir->buffer_pos] = samples[i];
+		if (++fir->buffer_pos == fir->ntaps)
+			fir->buffer_pos = 0;
+
+		/* convolve samples */
+		y = 0;
+		for (j = 0; j < fir->ntaps; j++) {
+			/* convolve sample from ring buffer, starting with oldes */
+			y += fir->buffer[fir->buffer_pos] * fir->taps[j];
+			if (++fir->buffer_pos == fir->ntaps)
+				fir->buffer_pos = 0;
+		}
+		samples[i] = y;
+	}
+}
+
+int fir_get_delay(fir_filter_t *fir)
+{
+	return fir->delay;
+}
+
diff --git a/src/libfilter/fir_filter.h b/src/libfilter/fir_filter.h
new file mode 100644
index 0000000..7d94091
--- /dev/null
+++ b/src/libfilter/fir_filter.h
@@ -0,0 +1,21 @@
+#ifndef _FIR_FILTER_H
+#define _FIR_FILTER_H
+
+typedef struct fir_filter {
+	int	ntaps;
+	int	delay;
+	double	*taps;
+	double	*buffer;
+	int	buffer_pos;
+} fir_filter_t;
+
+fir_filter_t *fir_lowpass_init(double samplerate, double cutoff, double transition_bandwidth);
+fir_filter_t *fir_highpass_init(double samplerate, double cutoff, double transition_bandwidth);
+fir_filter_t *fir_allpass_init(double samplerate, double transition_bandwidth);
+fir_filter_t *fir_twopass_init(double samplerate, double cutoff_low, double cutoff_high, double transition_bandwidth);
+void fir_exit(fir_filter_t *fir);
+void fir_process(fir_filter_t *fir, sample_t *samples, int num);
+int fir_get_delay(fir_filter_t *fir);
+
+#endif /* _FIR_FILTER_H */
+
diff --git a/src/libfilter/iir_filter.c b/src/libfilter/iir_filter.c
new file mode 100644
index 0000000..5872d61
--- /dev/null
+++ b/src/libfilter/iir_filter.c
@@ -0,0 +1,204 @@
+/* cut-off filter (biquad) based on Nigel Redmon (www.earlevel.com)
+ *
+ * (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
+ * All Rights Reserved
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include <math.h>
+#include "../libsample/sample.h"
+#include "iir_filter.h"
+
+//#define DEBUG_NAN
+
+#define PI M_PI
+
+void iir_lowpass_init(iir_filter_t *filter, double frequency, int samplerate, int iterations)
+{
+	double Fc, Q, K, norm;
+
+	if (iterations > 64) {
+		fprintf(stderr, "%s failed: too many iterations, please fix!\n", __func__);
+		abort();
+	}
+
+	memset(filter, 0, sizeof(*filter));
+	filter->iter = iterations;
+	Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */
+	Fc = frequency / (double)samplerate;
+	K = tan(PI * Fc);
+	norm = 1 / (1 + K / Q + K * K);
+	filter->a0 = K * K * norm;
+	filter->a1 = 2 * filter->a0;
+	filter->a2 = filter->a0;
+	filter->b1 = 2 * (K * K - 1) * norm;
+	filter->b2 = (1 - K / Q + K * K) * norm;
+#ifdef DEBUG_NAN
+	printf("%p\n", filter);
+#endif
+}
+
+void iir_highpass_init(iir_filter_t *filter, double frequency, int samplerate, int iterations)
+{
+	double Fc, Q, K, norm;
+
+	memset(filter, 0, sizeof(*filter));
+	filter->iter = iterations;
+	Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */
+	Fc = frequency / (double)samplerate;
+	K = tan(PI * Fc);
+	norm = 1 / (1 + K / Q + K * K);
+	filter->a0 = 1 * norm;
+	filter->a1 = -2 * filter->a0;
+	filter->a2 = filter->a0;
+	filter->b1 = 2 * (K * K - 1) * norm;
+	filter->b2 = (1 - K / Q + K * K) * norm;
+}
+
+void iir_bandpass_init(iir_filter_t *filter, double frequency, int samplerate, int iterations)
+{
+	double Fc, Q, K, norm;
+
+	memset(filter, 0, sizeof(*filter));
+	filter->iter = iterations;
+	Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */
+	Fc = frequency / (double)samplerate;
+	K = tan(PI * Fc);
+	norm = 1 / (1 + K / Q + K * K);
+	filter->a0 = K / Q * norm;
+	filter->a1 = 0;
+	filter->a2 = -filter->a0;
+	filter->b1 = 2 * (K * K - 1) * norm;
+	filter->b2 = (1 - K / Q + K * K) * norm;
+}
+
+void iir_notch_init(iir_filter_t *filter, double frequency, int samplerate, int iterations)
+{
+	double Fc, Q, K, norm;
+
+	memset(filter, 0, sizeof(*filter));
+	filter->iter = iterations;
+	Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */
+	Fc = frequency / (double)samplerate;
+	K = tan(PI * Fc);
+	norm = 1 / (1 + K / Q + K * K);
+	filter->a0 = (1 + K * K) * norm;
+	filter->a1 = 2 * (K * K - 1) * norm;
+	filter->a2 = filter->a0;
+	filter->b1 = filter->a1;
+	filter->b2 = (1 - K / Q + K * K) * norm;
+}
+
+void iir_process(iir_filter_t *filter, sample_t *samples, int length)
+{
+	double a0, a1, a2, b1, b2;
+	double *z1, *z2;
+	double in, out;
+	int iterations = filter->iter;
+	int i, j;
+
+	/* get states */
+	a0 = filter->a0;
+	a1 = filter->a1;
+	a2 = filter->a2;
+	b1 = filter->b1;
+	b2 = filter->b2;
+
+	/* these are state pointers, so no need to write back */
+	z1 = filter->z1;
+	z2 = filter->z2;
+
+	/* process filter */
+	for (i = 0; i < length; i++) {
+		/* add a small value, otherwise this loop will perform really bad on my 'nuedel' machine!!! */
+		in = *samples + 0.000000001;
+		for (j = 0; j < iterations; j++) {
+			out = in * a0 + z1[j];
+			z1[j] = in * a1 + z2[j] - b1 * out;
+			z2[j] = in * a2 - b2 * out;
+			in = out;
+		}
+		*samples++ = in;
+	}
+}
+
+#ifdef DEBUG_NAN
+#pragma GCC push_options
+//#pragma GCC optimize ("O0")
+#endif
+
+void iir_process_baseband(iir_filter_t *filter, float *baseband, int length)
+{
+	double a0, a1, a2, b1, b2;
+	double *z1, *z2;
+	double in, out;
+	int iterations = filter->iter;
+	int i, j;
+
+	/* get states */
+	a0 = filter->a0;
+	a1 = filter->a1;
+	a2 = filter->a2;
+	b1 = filter->b1;
+	b2 = filter->b2;
+
+	/* these are state pointers, so no need to write back */
+	z1 = filter->z1;
+	z2 = filter->z2;
+
+	/* process filter */
+	for (i = 0; i < length; i++) {
+		/* add a small value, otherwise this loop will perform really bad on my 'nuedel' machine!!! */
+		in = *baseband + 0.000000001;
+		for (j = 0; j < iterations; j++) {
+			out = in * a0 + z1[j];
+#ifdef DEBUG_NAN
+			if (!(out > -100 && out < 100)) {
+				printf("%p\n", filter);
+				printf("1. i=%d j=%d z=%.5f in=%.5f a0=%.5f out=%.5f\n", i, j, z1[j], in, a0, out);
+				abort();
+			}
+#endif
+			z1[j] = in * a1 + z2[j] - b1 * out;
+#ifdef DEBUG_NAN
+			if (!(z1[j] > -100 && z1[j] < 100)) {
+				printf("%p\n", filter);
+				printf("2. i=%d j=%d z1=%.5f z2=%.5f in=%.5f a1=%.5f out=%.5f b1=%.5f\n", i, j, z1[j], z2[j], in, a1, out, b1);
+				abort();
+			}
+#endif
+			z2[j] = in * a2 - b2 * out;
+#ifdef DEBUG_NAN
+			if (!(z2[j] > -100 && z2[j] < 100)) {
+				printf("%p\n", filter);
+				printf("%.5f\n", (in * a2) - (b2 * out));
+				printf("3. i=%d j=%d z2=%.5f in=%.5f a2=%.5f b2=%.5f out=%.5f\n", i, j, z2[j], in, a2, b2, out);
+				abort();
+			}
+#endif
+			in = out;
+		}
+		*baseband = in;
+		baseband += 2;
+	}
+}
+
+#ifdef DEBUG_NAN
+#pragma GCC pop_options
+#endif
diff --git a/src/libfilter/iir_filter.h b/src/libfilter/iir_filter.h
new file mode 100644
index 0000000..a5956c8
--- /dev/null
+++ b/src/libfilter/iir_filter.h
@@ -0,0 +1,17 @@
+#ifndef _FILTER_H
+#define _FILTER_H
+
+typedef struct iir_filter {
+	int iter;
+	double a0, a1, a2, b1, b2;
+	double z1[64], z2[64];
+} iir_filter_t;
+
+void iir_lowpass_init(iir_filter_t *filter, double frequency, int samplerate, int iterations);
+void iir_highpass_init(iir_filter_t *filter, double frequency, int samplerate, int iterations);
+void iir_bandpass_init(iir_filter_t *filter, double frequency, int samplerate, int iterations);
+void iir_notch_init(iir_filter_t *filter, double frequency, int samplerate, int iterations);
+void iir_process(iir_filter_t *filter, sample_t *samples, int length);
+void iir_process_baseband(iir_filter_t *filter, float *baseband, int length);
+
+#endif /* _FILTER_H */