1 /* -*- c-basic-offset: 2 -*-
3 * Copyright (C) 1999-2001 Erik Walthinsen <omega@cse.ogi.edu>
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Library General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Library General Public License for more details.
15 * You should have received a copy of the GNU Library General Public
16 * License along with this library; if not, write to the
17 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 * Boston, MA 02111-1307, USA.
21 /* this windowed sinc filter is taken from the freely downloadable DSP book,
22 * "The Scientist and Engineer's Guide to Digital Signal Processing",
24 * available at http://www.dspguide.com/
28 * - this filter is totally unoptimized !
29 * - we do not destroy the allocated memory for filters and residue
30 * - this might be improved upon with bytestream
34 #include "gstfilter.h"
35 #include <math.h> /* M_PI */
36 #include <string.h> /* memmove */
38 GstElementDetails gst_lpwsinc_details = {
40 "Filter/Audio/Effect",
41 "Low-pass Windowed sinc filter",
43 "Thomas <thomas@apestaart.org>",
44 "(C) 2002 Steven W. Smith",
58 #define GST_TYPE_LPWSINC \
59 (gst_lpwsinc_get_type())
60 #define GST_LPWSINC(obj) \
61 (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_LPWSINC,GstLPWSinc))
62 #define GST_LPWSINC_CLASS(klass) \
63 (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_ULAW,GstLPWSinc))
64 #define GST_IS_LPWSINC(obj) \
65 (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_LPWSINC))
66 #define GST_IS_LPWSINC_CLASS(obj) \
67 (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_LPWSINC))
69 typedef struct _GstLPWSinc GstLPWSinc;
70 typedef struct _GstLPWSincClass GstLPWSincClass;
76 GstPad *sinkpad, *srcpad;
79 int wing_size; /* length of a "wing" of the filter;
80 actual length is 2 * wing_size + 1 */
82 gfloat *residue; /* buffer for left-over samples from previous buffer */
86 struct _GstLPWSincClass
88 GstElementClass parent_class;
91 static void gst_lpwsinc_class_init (GstLPWSincClass * klass);
92 static void gst_lpwsinc_init (GstLPWSinc * filter);
94 static void gst_lpwsinc_set_property (GObject * object, guint prop_id,
97 static void gst_lpwsinc_get_property (GObject * object, guint prop_id,
98 GValue * value, GParamSpec * pspec);
100 static void gst_lpwsinc_chain (GstPad * pad, GstBuffer * buf);
101 static GstPadConnectReturn
102 gst_lpwsinc_sink_connect (GstPad * pad, GstCaps * caps);
104 static GstElementClass *parent_class = NULL;
105 /*static guint gst_lpwsinc_signals[LAST_SIGNAL] = { 0 }; */
107 GType gst_lpwsinc_get_type (void)
109 static GType lpwsinc_type = 0;
112 static const GTypeInfo lpwsinc_info = {
113 sizeof (GstLPWSincClass), NULL, NULL,
114 (GClassInitFunc) gst_lpwsinc_class_init, NULL, NULL,
115 sizeof (GstLPWSinc), 0,
116 (GInstanceInitFunc) gst_lpwsinc_init,
119 lpwsinc_type = g_type_register_static (GST_TYPE_ELEMENT, "GstLPWSinc",
126 gst_lpwsinc_class_init (GstLPWSincClass * klass)
128 GObjectClass *gobject_class;
129 GstElementClass *gstelement_class;
131 gobject_class = (GObjectClass *) klass;
132 gstelement_class = (GstElementClass *) klass;
134 parent_class = g_type_class_ref (GST_TYPE_ELEMENT);
136 g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_FREQUENCY,
137 g_param_spec_double ("frequency", "Frequency",
138 "Cut-off Frequency relative to sample rate)",
140 0, G_PARAM_READWRITE));
141 g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_LENGTH,
142 g_param_spec_int ("length", "Length",
143 "N such that the filter length = 2N + 1",
145 1, G_PARAM_READWRITE));
147 gobject_class->set_property = gst_lpwsinc_set_property;
148 gobject_class->get_property = gst_lpwsinc_get_property;
152 gst_lpwsinc_init (GstLPWSinc * filter)
154 filter->sinkpad = gst_pad_new_from_template (gst_filter_sink_factory (), "sink");
155 gst_pad_set_chain_function (filter->sinkpad, gst_lpwsinc_chain);
156 gst_pad_set_connect_function (filter->sinkpad, gst_lpwsinc_sink_connect);
157 gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);
159 filter->srcpad = gst_pad_new_from_template (gst_filter_src_factory (), "src");
160 gst_element_add_pad (GST_ELEMENT (filter), filter->srcpad);
162 filter->wing_size = 50;
163 filter->frequency = 0.25;
164 filter->kernel = NULL;
167 static GstPadConnectReturn
168 gst_lpwsinc_sink_connect (GstPad * pad, GstCaps * caps)
173 GstLPWSinc *filter = GST_LPWSINC (gst_pad_get_parent (pad));
174 GstPadConnectReturn set_retval;
176 g_assert (GST_IS_PAD (pad));
177 g_assert (caps != NULL);
179 if (!GST_CAPS_IS_FIXED (caps))
180 return GST_PAD_CONNECT_DELAYED;
182 set_retval = gst_pad_try_set_caps(filter->srcpad, caps);
186 /* connection works, so init the filter */
187 /* FIXME: remember to free it */
188 /* fill the kernel */
189 g_print ("DEBUG: initing filter kernel\n");
190 len = filter->wing_size;
191 GST_DEBUG (GST_CAT_PLUGIN_INFO,
192 "lpwsinc: initializing filter kernel of length %d", len * 2 + 1);
193 filter->kernel = (double *) g_malloc (sizeof (double) * (2 * len + 1));
195 for (i = 0; i <= len * 2; ++i)
198 filter->kernel[i] = 2 * M_PI * filter->frequency;
200 filter->kernel[i] = sin (2 * M_PI * filter->frequency * (i - len))
203 filter->kernel[i] *= (0.54 - 0.46 * cos (M_PI * i / len));
206 /* normalize for unity gain at DC
207 * FIXME: sure this is not supposed to be quadratic ? */
208 for (i = 0; i <= len * 2; ++i) sum += filter->kernel[i];
209 for (i = 0; i <= len * 2; ++i) filter->kernel[i] /= sum;
211 /* set up the residue memory space */
212 filter->residue = (gfloat *) g_malloc (sizeof (gfloat) * (len * 2 + 1));
213 for (i = 0; i <= len * 2; ++i) filter->residue[i] = 0.0;
220 gst_lpwsinc_chain (GstPad * pad, GstBuffer * buf)
225 gint residue_samples;
230 filter = GST_LPWSINC (gst_pad_get_parent (pad));
232 /* FIXME: out of laziness, we copy the left-over bit from last buffer
233 * together with the incoming buffer to a new buffer to make the loop
234 * easy; this could be a lot more optimized though
235 * to make amends we keep the incoming buffer around and write our
236 * output samples there */
238 /* get a writable buffer */
239 buf = gst_buffer_copy_on_write (buf);
241 src = (gfloat *) GST_BUFFER_DATA (buf);
242 residue_samples = filter->wing_size * 2 + 1;
243 input_samples = GST_BUFFER_SIZE (buf) / sizeof (gfloat);
244 total_samples = residue_samples + input_samples;
246 input = (gfloat *) g_malloc (sizeof (gfloat) * total_samples);
248 /* copy the left-over bit */
249 memcpy (input, filter->residue, sizeof (gfloat) * residue_samples);
251 /* copy the new buffer */
252 memcpy (&input[residue_samples], src, sizeof (gfloat) * input_samples);
253 /* copy the tail of the current input buffer to the residue */
254 memcpy (filter->residue, &src[input_samples - residue_samples],
255 sizeof (gfloat) * residue_samples);
258 /* since we copied the previous set of samples we needed before the actual
259 * input data, we need to add the filter length to our indices for input */
260 for (i = 0; i < input_samples; ++i)
263 for (j = 0; j < residue_samples; ++j)
264 src[i] += input[i - j + residue_samples] * filter->kernel[j];
268 gst_pad_push (filter->srcpad, buf);
272 gst_lpwsinc_set_property (GObject * object, guint prop_id, const GValue * value, GParamSpec * pspec)
276 /* it's not null if we got it, but it might not be ours */
277 g_return_if_fail (GST_IS_LPWSINC (object));
279 filter = GST_LPWSINC (object);
283 filter->wing_size = g_value_get_int (value);
286 filter->frequency = g_value_get_double (value);
294 gst_lpwsinc_get_property (GObject * object, guint prop_id, GValue * value, GParamSpec * pspec)
298 /* it's not null if we got it, but it might not be ours */
299 g_return_if_fail (GST_IS_LPWSINC (object));
301 filter = GST_LPWSINC (object);
305 g_value_set_int (value, filter->wing_size);
308 g_value_set_double (value, filter->frequency);
311 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);