1 /* GStreamer
2 * Copyright (C) 2009 Sebastian Droege <sebastian.droege@collabora.co.uk>
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
17 * Boston, MA 02110-1301, USA.
18 */
19
20 /* This small sample application creates a bandpass FIR filter
21 * by transforming the frequency response to the filter kernel.
22 */
23
24 /* FIXME 0.11: suppress warnings for deprecated API such as GValueArray
25 * with newer GLib versions (>= 2.31.0) */
26 #define GLIB_DISABLE_DEPRECATION_WARNINGS
27
28 #include <string.h>
29 #include <math.h>
30
31 #include <gst/gst.h>
32 #include <gst/fft/gstfftf64.h>
33
34 static gboolean
on_message(GstBus * bus,GstMessage * message,gpointer user_data)35 on_message (GstBus * bus, GstMessage * message, gpointer user_data)
36 {
37 GMainLoop *loop = (GMainLoop *) user_data;
38
39 switch (GST_MESSAGE_TYPE (message)) {
40 case GST_MESSAGE_ERROR:
41 g_error ("Got ERROR");
42 g_main_loop_quit (loop);
43 break;
44 case GST_MESSAGE_WARNING:
45 g_warning ("Got WARNING");
46 g_main_loop_quit (loop);
47 break;
48 case GST_MESSAGE_EOS:
49 g_main_loop_quit (loop);
50 break;
51 default:
52 break;
53 }
54
55 return TRUE;
56 }
57
58 static void
on_rate_changed(GstElement * element,gint rate,gpointer user_data)59 on_rate_changed (GstElement * element, gint rate, gpointer user_data)
60 {
61 GValueArray *va;
62 GValue v = { 0, };
63 GstFFTF64 *fft;
64 GstFFTF64Complex frequency_response[17];
65 gdouble tmp[32];
66 gdouble filter_kernel[32];
67 guint i;
68
69 /* Create the frequency response: zero outside
70 * a small frequency band */
71 for (i = 0; i < 17; i++) {
72 if (i < 5 || i > 11)
73 frequency_response[i].r = 0.0;
74 else
75 frequency_response[i].r = 1.0;
76
77 frequency_response[i].i = 0.0;
78 }
79
80 /* Calculate the inverse FT of the frequency response */
81 fft = gst_fft_f64_new (32, TRUE);
82 gst_fft_f64_inverse_fft (fft, frequency_response, tmp);
83 gst_fft_f64_free (fft);
84
85 /* Shift the inverse FT of the frequency response by 16,
86 * i.e. the half of the kernel length to get the
87 * impulse response. See http://www.dspguide.com/ch17/1.htm
88 * for more information.
89 */
90 for (i = 0; i < 32; i++)
91 filter_kernel[i] = tmp[(i + 16) % 32];
92
93 /* Apply the hamming window to the impulse response to get
94 * a better result than given from the rectangular window
95 */
96 for (i = 0; i < 32; i++)
97 filter_kernel[i] *= (0.54 - 0.46 * cos (2 * G_PI * i / 32));
98
99 va = g_value_array_new (1);
100
101 g_value_init (&v, G_TYPE_DOUBLE);
102 for (i = 0; i < 32; i++) {
103 g_value_set_double (&v, filter_kernel[i]);
104 g_value_array_append (va, &v);
105 g_value_reset (&v);
106 }
107 g_object_set (G_OBJECT (element), "kernel", va, NULL);
108 /* Latency is 1/2 of the kernel length for this method of
109 * calculating a filter kernel from the frequency response
110 */
111 g_object_set (G_OBJECT (element), "latency", (gint64) (32 / 2), NULL);
112 g_value_array_free (va);
113 }
114
115 gint
main(gint argc,gchar * argv[])116 main (gint argc, gchar * argv[])
117 {
118 GstElement *pipeline, *src, *filter, *conv, *sink;
119 GstBus *bus;
120 GMainLoop *loop;
121
122 gst_init (NULL, NULL);
123
124 pipeline = gst_element_factory_make ("pipeline", NULL);
125
126 src = gst_element_factory_make ("audiotestsrc", NULL);
127 g_object_set (G_OBJECT (src), "wave", 5, NULL);
128
129 filter = gst_element_factory_make ("audiofirfilter", NULL);
130 g_signal_connect (G_OBJECT (filter), "rate-changed",
131 G_CALLBACK (on_rate_changed), NULL);
132
133 conv = gst_element_factory_make ("audioconvert", NULL);
134
135 sink = gst_element_factory_make ("autoaudiosink", NULL);
136 g_return_val_if_fail (sink != NULL, -1);
137
138 gst_bin_add_many (GST_BIN (pipeline), src, filter, conv, sink, NULL);
139 if (!gst_element_link_many (src, filter, conv, sink, NULL)) {
140 g_error ("Failed to link elements");
141 return -2;
142 }
143
144 loop = g_main_loop_new (NULL, FALSE);
145
146 bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
147 gst_bus_add_signal_watch (bus);
148 g_signal_connect (G_OBJECT (bus), "message", G_CALLBACK (on_message), loop);
149 gst_object_unref (GST_OBJECT (bus));
150
151 if (gst_element_set_state (pipeline,
152 GST_STATE_PLAYING) == GST_STATE_CHANGE_FAILURE) {
153 g_error ("Failed to go into PLAYING state");
154 return -3;
155 }
156
157 g_main_loop_run (loop);
158
159 gst_element_set_state (pipeline, GST_STATE_NULL);
160
161 g_main_loop_unref (loop);
162 gst_object_unref (pipeline);
163
164 return 0;
165 }
166