--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gst_plugins_base/tests/examples/volume/volume.c	Thu Dec 17 08:53:32 2009 +0200
@@ -0,0 +1,172 @@
+/* GStreamer
+ *
+ * volume.c: sample application to change the volume of a pipeline
+ *
+ * Copyright (C) <2004> Thomas Vander Stichele <thomas at apestaart dot org>
+ *
+ * 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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <math.h>
+
+#include <gst/gst.h>
+#include <gtk/gtk.h>
+
+/* global pointer for the scale widget */
+GtkWidget *elapsed;
+GtkWidget *scale;
+
+#ifndef M_LN10
+#define M_LN10 (log(10.0))
+#endif
+
+static void
+value_changed_callback (GtkWidget * widget, GstElement * volume)
+{
+  gdouble value;
+  gdouble level;
+
+  value = gtk_range_get_value (GTK_RANGE (widget));
+  level = exp (value / 20.0 * M_LN10);
+  g_print ("Value: %f dB, level: %f\n", value, level);
+  g_object_set (volume, "volume", level, NULL);
+}
+
+static void
+setup_gui (GstElement * volume)
+{
+  GtkWidget *window;
+  GtkWidget *vbox;
+  GtkWidget *label, *hbox;
+
+  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  g_signal_connect (window, "destroy", gtk_main_quit, NULL);
+
+  vbox = gtk_vbox_new (TRUE, 0);
+  gtk_container_add (GTK_CONTAINER (window), vbox);
+
+  /* elapsed widget */
+  hbox = gtk_hbox_new (TRUE, 0);
+  label = gtk_label_new ("Elapsed");
+  elapsed = gtk_label_new ("0.000");
+  gtk_container_add (GTK_CONTAINER (hbox), label);
+  gtk_container_add (GTK_CONTAINER (hbox), elapsed);
+  gtk_container_add (GTK_CONTAINER (vbox), hbox);
+
+  /* volume */
+  hbox = gtk_hbox_new (TRUE, 0);
+  label = gtk_label_new ("volume");
+  gtk_container_add (GTK_CONTAINER (hbox), label);
+  scale = gtk_hscale_new_with_range (-90.0, 10.0, 0.2);
+  gtk_range_set_value (GTK_RANGE (scale), 0.0);
+  gtk_widget_set_size_request (scale, 100, -1);
+  gtk_container_add (GTK_CONTAINER (hbox), scale);
+  gtk_container_add (GTK_CONTAINER (vbox), hbox);
+  g_signal_connect (scale, "value-changed",
+      G_CALLBACK (value_changed_callback), volume);
+
+  gtk_widget_show_all (GTK_WIDGET (window));
+}
+
+static void
+message_received (GstBus * bus, GstMessage * message, GstPipeline * pipeline)
+{
+  const GstStructure *s;
+
+  s = gst_message_get_structure (message);
+  g_print ("message from \"%s\" (%s): ",
+      GST_STR_NULL (GST_ELEMENT_NAME (GST_MESSAGE_SRC (message))),
+      gst_message_type_get_name (GST_MESSAGE_TYPE (message)));
+  if (s) {
+    gchar *sstr;
+
+    sstr = gst_structure_to_string (s);
+    g_print ("%s\n", sstr);
+    g_free (sstr);
+  } else {
+    g_print ("no message details\n");
+  }
+}
+
+static void
+eos_message_received (GstBus * bus, GstMessage * message,
+    GstPipeline * pipeline)
+{
+  message_received (bus, message, pipeline);
+  gtk_main_quit ();
+}
+
+int
+main (int argc, char *argv[])
+{
+
+  GstElement *pipeline = NULL;
+
+#ifndef GST_DISABLE_PARSE
+  GError *error = NULL;
+#endif
+  GstElement *volume;
+  GstBus *bus;
+
+#ifdef GST_DISABLE_PARSE
+  g_print ("GStreamer was built without pipeline parsing capabilities.\n");
+  g_print
+      ("Please rebuild GStreamer with pipeline parsing capabilities activated to use this example.\n");
+  return 1;
+#else
+  gst_init (&argc, &argv);
+  gtk_init (&argc, &argv);
+
+  pipeline = gst_parse_launchv ((const gchar **) &argv[1], &error);
+  if (error) {
+    g_print ("pipeline could not be constructed: %s\n", error->message);
+    g_print ("Please give a complete pipeline  with a 'volume' element.\n");
+    g_print ("Example: audiotestsrc ! volume ! %s\n", DEFAULT_AUDIOSINK);
+    g_error_free (error);
+    return 1;
+  }
+#endif
+  volume = gst_bin_get_by_name (GST_BIN (pipeline), "volume0");
+  if (volume == NULL) {
+    g_print ("Please give a pipeline with a 'volume' element in it\n");
+    return 1;
+  }
+
+  /* setup message handling */
+  bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
+  gst_bus_add_signal_watch_full (bus, G_PRIORITY_HIGH);
+  g_signal_connect (bus, "message::error", (GCallback) message_received,
+      pipeline);
+  g_signal_connect (bus, "message::warning", (GCallback) message_received,
+      pipeline);
+  g_signal_connect (bus, "message::eos", (GCallback) eos_message_received,
+      pipeline);
+
+  /* setup GUI */
+  setup_gui (volume);
+
+  /* go to main loop */
+  gst_element_set_state (pipeline, GST_STATE_PLAYING);
+  gtk_main ();
+  gst_element_set_state (pipeline, GST_STATE_NULL);
+  gst_object_unref (pipeline);
+
+  return 0;
+}