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
37 #include "gstfilter.h"
38 #include <math.h> /* M_PI */
39 #include <string.h> /* memmove */
41 GstElementDetails gst_lpwsinc_details = {
43 "Filter/Audio/Effect",
45 "Low-pass Windowed sinc filter",
47 "Thomas <thomas@apestaart.org>",
48 "(C) 2002 Steven W. Smith",
62 #define GST_TYPE_LPWSINC \
63 (gst_lpwsinc_get_type())
64 #define GST_LPWSINC(obj) \
65 (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_LPWSINC,GstLPWSinc))
66 #define GST_LPWSINC_CLASS(klass) \
67 (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_ULAW,GstLPWSinc))
68 #define GST_IS_LPWSINC(obj) \
69 (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_LPWSINC))
70 #define GST_IS_LPWSINC_CLASS(obj) \
71 (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_LPWSINC))
73 typedef struct _GstLPWSinc GstLPWSinc;
74 typedef struct _GstLPWSincClass GstLPWSincClass;
80 GstPad *sinkpad, *srcpad;
83 int wing_size; /* length of a "wing" of the filter;
84 actual length is 2 * wing_size + 1 */
86 gfloat *residue; /* buffer for left-over samples from previous buffer */
90 struct _GstLPWSincClass
92 GstElementClass parent_class;
95 static void gst_lpwsinc_class_init (GstLPWSincClass * klass);
96 static void gst_lpwsinc_init (GstLPWSinc * filter);
98 static void gst_lpwsinc_set_property (GObject * object, guint prop_id,
101 static void gst_lpwsinc_get_property (GObject * object, guint prop_id,
102 GValue * value, GParamSpec * pspec);
104 static void gst_lpwsinc_chain (GstPad * pad, GstBuffer * buf);
105 static GstPadLinkReturn
106 gst_lpwsinc_sink_connect (GstPad * pad, GstCaps * caps);
108 static GstElementClass *parent_class = NULL;
109 /*static guint gst_lpwsinc_signals[LAST_SIGNAL] = { 0 }; */
111 GType gst_lpwsinc_get_type (void)
113 static GType lpwsinc_type = 0;
116 static const GTypeInfo lpwsinc_info = {
117 sizeof (GstLPWSincClass), NULL, NULL,
118 (GClassInitFunc) gst_lpwsinc_class_init, NULL, NULL,
119 sizeof (GstLPWSinc), 0,
120 (GInstanceInitFunc) gst_lpwsinc_init,
123 lpwsinc_type = g_type_register_static (GST_TYPE_ELEMENT, "GstLPWSinc",
130 gst_lpwsinc_class_init (GstLPWSincClass * klass)
132 GObjectClass *gobject_class;
133 GstElementClass *gstelement_class;
135 gobject_class = (GObjectClass *) klass;
136 gstelement_class = (GstElementClass *) klass;
138 parent_class = g_type_class_ref (GST_TYPE_ELEMENT);
140 g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_FREQUENCY,
141 g_param_spec_double ("frequency", "Frequency",
142 "Cut-off Frequency relative to sample rate)",
144 0, G_PARAM_READWRITE));
145 g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_LENGTH,
146 g_param_spec_int ("length", "Length",
147 "N such that the filter length = 2N + 1",
149 1, G_PARAM_READWRITE));
151 gobject_class->set_property = gst_lpwsinc_set_property;
152 gobject_class->get_property = gst_lpwsinc_get_property;
156 gst_lpwsinc_init (GstLPWSinc * filter)
158 filter->sinkpad = gst_pad_new_from_template (gst_filter_sink_factory (), "sink");
159 gst_pad_set_chain_function (filter->sinkpad, gst_lpwsinc_chain);
160 gst_pad_set_link_function (filter->sinkpad, gst_lpwsinc_sink_connect);
161 gst_element_add_pad (GST_ELEMENT (filter), filter->sinkpad);
163 filter->srcpad = gst_pad_new_from_template (gst_filter_src_factory (), "src");
164 gst_element_add_pad (GST_ELEMENT (filter), filter->srcpad);
166 filter->wing_size = 50;
167 filter->frequency = 0.25;
168 filter->kernel = NULL;
171 static GstPadLinkReturn
172 gst_lpwsinc_sink_connect (GstPad * pad, GstCaps * caps)
177 GstLPWSinc *filter = GST_LPWSINC (gst_pad_get_parent (pad));
178 GstPadLinkReturn set_retval;
180 g_assert (GST_IS_PAD (pad));
181 g_assert (caps != NULL);
183 if (!GST_CAPS_IS_FIXED (caps))
184 return GST_PAD_LINK_DELAYED;
186 set_retval = gst_pad_try_set_caps(filter->srcpad, caps);
190 /* connection works, so init the filter */
191 /* FIXME: remember to free it */
192 /* fill the kernel */
193 g_print ("DEBUG: initing filter kernel\n");
194 len = filter->wing_size;
196 "lpwsinc: initializing filter kernel of length %d", len * 2 + 1);
197 filter->kernel = (double *) g_malloc (sizeof (double) * (2 * len + 1));
199 for (i = 0; i <= len * 2; ++i)
202 filter->kernel[i] = 2 * M_PI * filter->frequency;
204 filter->kernel[i] = sin (2 * M_PI * filter->frequency * (i - len))
207 filter->kernel[i] *= (0.54 - 0.46 * cos (M_PI * i / len));
210 /* normalize for unity gain at DC
211 * FIXME: sure this is not supposed to be quadratic ? */
212 for (i = 0; i <= len * 2; ++i) sum += filter->kernel[i];
213 for (i = 0; i <= len * 2; ++i) filter->kernel[i] /= sum;
215 /* set up the residue memory space */
216 filter->residue = (gfloat *) g_malloc (sizeof (gfloat) * (len * 2 + 1));
217 for (i = 0; i <= len * 2; ++i) filter->residue[i] = 0.0;
224 gst_lpwsinc_chain (GstPad * pad, GstBuffer * buf)
229 gint residue_samples;
234 filter = GST_LPWSINC (gst_pad_get_parent (pad));
236 /* FIXME: out of laziness, we copy the left-over bit from last buffer
237 * together with the incoming buffer to a new buffer to make the loop
238 * easy; this could be a lot more optimized though
239 * to make amends we keep the incoming buffer around and write our
240 * output samples there */
242 /* get a writable buffer */
243 buf = gst_buffer_copy_on_write (buf);
245 src = (gfloat *) GST_BUFFER_DATA (buf);
246 residue_samples = filter->wing_size * 2 + 1;
247 input_samples = GST_BUFFER_SIZE (buf) / sizeof (gfloat);
248 total_samples = residue_samples + input_samples;
250 input = (gfloat *) g_malloc (sizeof (gfloat) * total_samples);
252 /* copy the left-over bit */
253 memcpy (input, filter->residue, sizeof (gfloat) * residue_samples);
255 /* copy the new buffer */
256 memcpy (&input[residue_samples], src, sizeof (gfloat) * input_samples);
257 /* copy the tail of the current input buffer to the residue */
258 memcpy (filter->residue, &src[input_samples - residue_samples],
259 sizeof (gfloat) * residue_samples);
262 /* since we copied the previous set of samples we needed before the actual
263 * input data, we need to add the filter length to our indices for input */
264 for (i = 0; i < input_samples; ++i)
267 for (j = 0; j < residue_samples; ++j)
268 src[i] += input[i - j + residue_samples] * filter->kernel[j];
272 gst_pad_push (filter->srcpad, buf);
276 gst_lpwsinc_set_property (GObject * object, guint prop_id, const GValue * value, GParamSpec * pspec)
280 /* it's not null if we got it, but it might not be ours */
281 g_return_if_fail (GST_IS_LPWSINC (object));
283 filter = GST_LPWSINC (object);
287 filter->wing_size = g_value_get_int (value);
290 filter->frequency = g_value_get_double (value);
298 gst_lpwsinc_get_property (GObject * object, guint prop_id, GValue * value, GParamSpec * pspec)
302 /* it's not null if we got it, but it might not be ours */
303 g_return_if_fail (GST_IS_LPWSINC (object));
305 filter = GST_LPWSINC (object);
309 g_value_set_int (value, filter->wing_size);
312 g_value_set_double (value, filter->frequency);
315 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);