[tslib] [PATCH] plugins: add IIR filter plugin
Martin Kepplinger
martink at posteo.de
Tue Mar 28 02:17:38 PDT 2017
From: Martin Kepplinger <martin.kepplinger at ginzinger.com>
Fixes #86
---
I found this very nice filter and thought why not implement it for us. It's
actually a must-have I think. It's really cheap in resourses and very effective,
and quite fun to play with. Choose 9/10 and see for yourself.
I'd be happy for feedback. Posted to the list for future reference too, to
demonstrate how to add a new filter.
README.md | 21 ++++
configure.ac | 1 +
etc/ts.conf | 3 +
plugins/Makefile.am | 14 +++
plugins/iir.c | 267 +++++++++++++++++++++++++++++++++++++++++++++++++++
plugins/plugins.h | 1 +
src/Makefile.am | 4 +
src/ts_load_module.c | 3 +
8 files changed, 314 insertions(+)
create mode 100644 plugins/iir.c
diff --git a/README.md b/README.md
index 8e1423a..ff1dbb7 100644
--- a/README.md
+++ b/README.md
@@ -182,6 +182,27 @@ Parameters:
Maximum pressure value for a sample to be valid.
+### module: iir
+
+#### Description:
+ Infinite impulse response filter. Similar to dejitter, this is a smoothing
+ filter to remove low-level noise. There is a trade-off between noise removal
+ (smoothing) and responsiveness. The parameters N and D specify the level of
+ smoothing in the form of a fraction (N/D).
+
+ [Wikipedia](https://en.wikipedia.org/wiki/Infinite_impulse_response) has some
+ general theory.
+
+
+Parameters:
+* `N`
+
+ numerator of the smoothing fraction
+* `D`
+
+ denominator of the smoothing fraction
+
+
### module: dejitter
#### Description:
diff --git a/configure.ac b/configure.ac
index 122b80e..153cbc1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -97,6 +97,7 @@ TSLIB_CHECK_MODULE([median], [yes], [Enable building of median filter])
TSLIB_CHECK_MODULE([pthres], [yes], [Enable building of pthres filter])
TSLIB_CHECK_MODULE([debounce], [yes], [Enable building of debounce filter])
TSLIB_CHECK_MODULE([skip], [yes], [Enable building of skip filter])
+TSLIB_CHECK_MODULE([iir], [yes], [Enable building of IIR filter])
# hardware access modules
if test "$build_linux" = "yes"; then
diff --git a/etc/ts.conf b/etc/ts.conf
index c63ff12..4f69b1a 100644
--- a/etc/ts.conf
+++ b/etc/ts.conf
@@ -44,6 +44,9 @@ module pthres pmin=1
# Uncomment if needed to filter spikes
# module median depth=5
+# Uncomment to enable smoothing of fraction N/D
+# module iir N=6 D=10
+
# Uncomment if needed (single touch only)
# module variance delta=30
diff --git a/plugins/Makefile.am b/plugins/Makefile.am
index 8c999ba..7c640b4 100644
--- a/plugins/Makefile.am
+++ b/plugins/Makefile.am
@@ -59,6 +59,12 @@ else
SKIP_MODULE =
endif
+if ENABLE_IIR_MODULE
+IIR_MODULE = iir.la
+else
+IIR_MODULE =
+endif
+
if ENABLE_UCB1X00_MODULE
UCB1X00_MODULE = ucb1x00.la
else
@@ -152,6 +158,7 @@ pluginexec_LTLIBRARIES = \
$(PTHRES_MODULE) \
$(DEBOUNCE_MODULE) \
$(SKIP_MODULE) \
+ $(IIR_MODULE) \
$(UCB1X00_MODULE) \
$(CORGI_MODULE) \
$(COLLIE_MODULE) \
@@ -223,6 +230,13 @@ linear_h2200_la_LDFLAGS += -no-undefined
endif
linear_h2200_la_LIBADD = $(top_builddir)/src/libts.la
+iir_la_SOURCES = iir.c
+iir_la_LDFLAGS = -module $(LTVSN)
+if WINDOWS
+iir_la_LDFLAGS += -no-undefined
+endif
+iir_la_LIBADD = $(top_builddir)/src/libts.la
+
# hw access
corgi_la_SOURCES = corgi-raw.c
corgi_la_LDFLAGS = -module $(LTVSN)
diff --git a/plugins/iir.c b/plugins/iir.c
new file mode 100644
index 0000000..af3ecd2
--- /dev/null
+++ b/plugins/iir.c
@@ -0,0 +1,267 @@
+/*
+ * tslib/plugins/iir.c
+ *
+ * Copyright (C) 2017 Martin Kepplinger
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 2 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * Similar to dejitter, this is a smoothing filter to remove low-level noise.
+ * See https://en.wikipedia.org/wiki/Infinite_impulse_response for some theory.
+ * There is a trade-off between noise removal (smoothing) and responsiveness:
+ * The parameters N and D specify the level of smoothing in the form of a
+ * fraction (N/D).
+ *
+ * The discrete formula we use is found at http://dlbeer.co.nz/articles/tsf.html
+ */
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include <stdint.h>
+
+#include <stdio.h>
+
+#include "config.h"
+#include "tslib.h"
+#include "tslib-filter.h"
+
+struct tslib_iir {
+ struct tslib_module_info module;
+ uint32_t D;
+ uint32_t N;
+ int32_t slots;
+ uint32_t nr;
+ int32_t s;
+ int32_t t;
+ uint8_t last_active; /* for finding pen-down */
+
+ int32_t *s_mt;
+ int32_t *t_mt;
+ uint8_t *last_active_mt; /* for finding pen-down */
+};
+
+/* legacy read interface */
+static int iir_read(struct tslib_module_info *info, struct ts_sample *samp,
+ int nr)
+{
+ struct tslib_iir *iir = (struct tslib_iir *)info;
+ int32_t ret;
+ int32_t i;
+
+ ret = info->next->ops->read(info->next, samp, nr);
+ if (ret < 0)
+ return ret;
+
+ for (i = 0; i < ret; i++, samp++) {
+ if (samp->pressure == 0) { /* reset */
+ iir->s = samp->x;
+ iir->t = samp->y;
+ iir->last_active = 0;
+ continue;
+ } else if (iir->last_active == 0) {
+ iir->s = samp->x;
+ iir->t = samp->y;
+ iir->last_active = 1;
+ continue;
+ }
+
+ iir->s = (iir->N * iir->s + (iir->D - iir->N) * samp->x + iir->D / 2) / iir->D;
+ #ifdef DEBUG
+ printf("IIR: X: %d -> %d\n", samp->x, iir->s);
+ #endif
+ samp->x = iir->s;
+
+ iir->t = (iir->N * iir->t + (iir->D - iir->N) * samp->y + iir->D / 2) / iir->D;
+ #ifdef DEBUG
+ printf("IIR: Y: %d -> %d\n", samp->y, iir->t);
+ #endif
+ samp->y = iir->t;
+ }
+
+ return ret;
+}
+
+static int iir_read_mt(struct tslib_module_info *info,
+ struct ts_sample_mt **samp, int max_slots, int nr)
+{
+ struct tslib_iir *iir = (struct tslib_iir *)info;
+ int32_t ret;
+ int32_t i, j;
+
+ if (!iir->s_mt || max_slots > iir->slots) {
+ if (iir->s_mt)
+ free(iir->s_mt);
+
+ if (iir->t_mt)
+ free(iir->t_mt);
+
+ if (iir->last_active_mt)
+ free(iir->last_active_mt);
+
+ iir->s_mt = calloc(max_slots, sizeof(int32_t));
+ if (!iir->s_mt)
+ return -ENOMEM;
+
+ iir->t_mt = calloc(max_slots, sizeof(int32_t));
+ if (!iir->t_mt)
+ return -ENOMEM;
+
+ iir->last_active_mt = calloc(max_slots, sizeof(uint8_t));
+ if (!iir->last_active_mt)
+ return -ENOMEM;
+
+ iir->slots = max_slots;
+ }
+
+ ret = info->next->ops->read_mt(info->next, samp, max_slots, nr);
+ if (ret < 0)
+ return ret;
+
+ for (i = 0; i < ret; i++) {
+ for (j = 0; j < max_slots; j++) {
+ if (samp[i][j].valid != 1)
+ continue;
+ /* reset */
+ if (samp[i][j].pressure == 0) { /* pen-up */
+ iir->s_mt[j] = samp[i][j].x;
+ iir->t_mt[j] = samp[i][j].y;
+ iir->last_active_mt[j] = 0;
+ continue;
+ } else if (iir->last_active_mt[j] == 0) { /* pen-down */
+ iir->s_mt[j] = samp[i][j].x;
+ iir->t_mt[j] = samp[i][j].y;
+ iir->last_active_mt[j] = 1;
+ continue;
+ }
+
+ iir->s_mt[j] = (iir->N * iir->s_mt[j] +
+ (iir->D - iir->N) * samp[i][j].x +
+ iir->D / 2)
+ / iir->D;
+ #ifdef DEBUG
+ printf("IIR: (slot %d) X: %d -> %d\n",
+ j, samp[i][j].x, iir->s_mt[j]);
+ #endif
+ samp[i][j].x = iir->s_mt[j];
+
+ iir->t_mt[j] = (iir->N * iir->t_mt[j] +
+ (iir->D - iir->N) * samp[i][j].y +
+ iir->D / 2)
+ / iir->D;
+ #ifdef DEBUG
+ printf("IIR: (slot %d) Y: %d -> %d\n",
+ j, samp[i][j].y, iir->t_mt[j]);
+ #endif
+ samp[i][j].y = iir->t_mt[j];
+ }
+ }
+
+ return ret;
+}
+
+static int iir_fini(struct tslib_module_info *info)
+{
+ struct tslib_iir *iir = (struct tslib_iir *)info;
+
+ if (iir->s_mt)
+ free(iir->s_mt);
+
+ if (iir->t_mt)
+ free(iir->t_mt);
+
+ free(info);
+
+ return 0;
+}
+
+static const struct tslib_ops iir_ops = {
+ .read = iir_read,
+ .read_mt = iir_read_mt,
+ .fini = iir_fini,
+};
+
+static int iir_opt(struct tslib_module_info *inf, char *str, void *data)
+{
+ struct tslib_iir *iir = (struct tslib_iir *)inf;
+ unsigned long v;
+ int32_t err = errno;
+
+ v = strtoul(str, NULL, 0);
+
+ if (v == ULONG_MAX && errno == ERANGE)
+ return -1;
+
+ errno = err;
+ switch ((int)(intptr_t)data) {
+ case 1:
+ iir->N = v;
+ break;
+
+ case 2:
+ iir->D = v;
+ if (iir->D == 0) {
+ printf("IIR: avoid division by zero: D=1 set\n");
+ iir->D = 1;
+ }
+ break;
+
+ default:
+ return -1;
+ }
+
+
+ return 0;
+}
+
+static const struct tslib_vars iir_vars[] = {
+ { "N", (void *)1, iir_opt },
+ { "D", (void *)2, iir_opt },
+};
+
+#define NR_VARS (sizeof(iir_vars) / sizeof(iir_vars[0]))
+
+TSAPI struct tslib_module_info *iir_mod_init(__attribute__ ((unused)) struct tsdev *dev,
+ const char *params)
+{
+ struct tslib_iir *iir;
+
+ iir = malloc(sizeof(struct tslib_iir));
+ if (iir == NULL)
+ return NULL;
+
+ memset(iir, 0, sizeof(struct tslib_iir));
+ iir->module.ops = &iir_ops;
+
+ iir->N = 0;
+ iir->D = 0;
+ iir->slots = 0;
+ iir->nr = 0;
+ iir->s = 0;
+ iir->t = 0;
+ iir->s_mt = NULL;
+ iir->t_mt = NULL;
+ iir->last_active = 0;
+
+ if (tslib_parse_vars(&iir->module, iir_vars, NR_VARS, params)) {
+ free(iir);
+ return NULL;
+ }
+
+ return &iir->module;
+}
+
+#ifndef TSLIB_STATIC_DEJITTER_MODULE
+ TSLIB_MODULE_INIT(iir_mod_init);
+#endif
diff --git a/plugins/plugins.h b/plugins/plugins.h
index 01d39a2..8f9f5d2 100644
--- a/plugins/plugins.h
+++ b/plugins/plugins.h
@@ -9,6 +9,7 @@ TSLIB_DECLARE_MODULE(median);
TSLIB_DECLARE_MODULE(pthres);
TSLIB_DECLARE_MODULE(debounce);
TSLIB_DECLARE_MODULE(skip);
+TSLIB_DECLARE_MODULE(iir);
TSLIB_DECLARE_MODULE(ucb1x00);
TSLIB_DECLARE_MODULE(corgi);
diff --git a/src/Makefile.am b/src/Makefile.am
index 8aa80c4..ec0f539 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -86,6 +86,10 @@ if ENABLE_STATIC_SKIP_MODULE
libts_la_SOURCES += $(top_srcdir)/plugins/skip.c
endif
+if ENABLE_STATIC_IIR_MODULE
+libts_la_SOURCES += $(top_srcdir)/plugins/iir.c
+endif
+
if ENABLE_STATIC_WAVESHARE_MODULE
libts_la_SOURCES += $(top_srcdir)/plugins/waveshare-raw.c
endif
diff --git a/src/ts_load_module.c b/src/ts_load_module.c
index a178d19..c0e1f39 100644
--- a/src/ts_load_module.c
+++ b/src/ts_load_module.c
@@ -77,6 +77,9 @@ static const struct {
#ifdef TSLIB_STATIC_SKIP_MODULE
{ "skip", skip_mod_init },
#endif
+#ifdef TSLIB_STATIC_IIR_MODULE
+ { "iir", iir_mod_init },
+#endif
};
#define countof(arr) (sizeof(arr) / sizeof((arr)[0]))
--
2.1.4
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