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/* GStreamer
* Copyright (C) 2009 Sebastian Droege <sebastian.droege@collabora.co.uk>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/* This small sample application creates a bandpass FIR filter
* by transforming the frequency response to the filter kernel.
*/
#include <string.h>
#include <math.h>
#include <gst/gst.h>
#include <gst/fft/gstfftf64.h>
static gboolean
on_message (GstBus * bus, GstMessage * message, gpointer user_data)
{
GMainLoop *loop = (GMainLoop *) user_data;
switch (GST_MESSAGE_TYPE (message)) {
case GST_MESSAGE_ERROR:
g_error ("Got ERROR");
g_main_loop_quit (loop);
break;
case GST_MESSAGE_WARNING:
g_warning ("Got WARNING");
g_main_loop_quit (loop);
break;
case GST_MESSAGE_EOS:
g_main_loop_quit (loop);
break;
default:
break;
}
return TRUE;
}
static void
on_rate_changed (GstElement * element, gint rate, gpointer user_data)
{
GValueArray *va;
GValue v = { 0, };
GstFFTF64 *fft;
GstFFTF64Complex frequency_response[17];
gdouble tmp[32];
gdouble filter_kernel[32];
guint i;
/* Create the frequency response: zero outside
* a small frequency band */
for (i = 0; i < 17; i++) {
if (i < 5 || i > 11)
frequency_response[i].r = 0.0;
else
frequency_response[i].r = 1.0;
frequency_response[i].i = 0.0;
}
/* Calculate the inverse FT of the frequency response */
fft = gst_fft_f64_new (32, TRUE);
gst_fft_f64_inverse_fft (fft, frequency_response, tmp);
gst_fft_f64_free (fft);
/* Shift the inverse FT of the frequency response by 16,
* i.e. the half of the kernel length to get the
* impulse response. See http://www.dspguide.com/ch17/1.htm
* for more information.
*/
for (i = 0; i < 32; i++)
filter_kernel[i] = tmp[(i + 16) % 32];
/* Apply the hamming window to the impulse response to get
* a better result than given from the rectangular window
*/
for (i = 0; i < 32; i++)
filter_kernel[i] *= (0.54 - 0.46 * cos (2 * M_PI * i / 32));
va = g_value_array_new (1);
g_value_init (&v, G_TYPE_DOUBLE);
for (i = 0; i < 32; i++) {
g_value_set_double (&v, filter_kernel[i]);
g_value_array_append (va, &v);
g_value_reset (&v);
}
g_object_set (G_OBJECT (element), "kernel", va, NULL);
/* Latency is 1/2 of the kernel length for this method of
* calculating a filter kernel from the frequency response
*/
g_object_set (G_OBJECT (element), "latency", 32 / 2, NULL);
g_value_array_free (va);
}
gint
main (gint argc, gchar * argv[])
{
GstElement *pipeline, *src, *filter, *conv, *sink;
GstBus *bus;
GMainLoop *loop;
gst_init (NULL, NULL);
pipeline = gst_element_factory_make ("pipeline", NULL);
src = gst_element_factory_make ("audiotestsrc", NULL);
g_object_set (G_OBJECT (src), "wave", 5, NULL);
filter = gst_element_factory_make ("audiofirfilter", NULL);
g_signal_connect (G_OBJECT (filter), "rate-changed",
G_CALLBACK (on_rate_changed), NULL);
conv = gst_element_factory_make ("audioconvert", NULL);
sink = gst_element_factory_make ("autoaudiosink", NULL);
g_return_val_if_fail (sink != NULL, -1);
gst_bin_add_many (GST_BIN (pipeline), src, filter, conv, sink, NULL);
if (!gst_element_link_many (src, filter, conv, sink, NULL)) {
g_error ("Failed to link elements");
return -2;
}
loop = g_main_loop_new (NULL, FALSE);
bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
gst_bus_add_signal_watch (bus);
g_signal_connect (G_OBJECT (bus), "message", G_CALLBACK (on_message), loop);
gst_object_unref (GST_OBJECT (bus));
if (gst_element_set_state (pipeline,
GST_STATE_PLAYING) == GST_STATE_CHANGE_FAILURE) {
g_error ("Failed to go into PLAYING state");
return -3;
}
g_main_loop_run (loop);
gst_element_set_state (pipeline, GST_STATE_NULL);
g_main_loop_unref (loop);
gst_object_unref (pipeline);
return 0;
}
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