3 * Copyright (C) 2007 Sebastian Dröge <slomo@circular-chaos.org>
5 * gstcontrolsource.c: Interface declaration for control sources
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License along with this library; if not, write to the
19 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 * Boston, MA 02111-1307, USA.
24 * SECTION:gstcontrolsource
25 * @short_description: base class for control source sources
27 * The #GstControlSource is a base class for control value sources that could
28 * be used by #GstController to get timestamp-value pairs.
30 * A #GstControlSource is used by first getting an instance, binding it to a
31 * #GParamSpec (for example by using gst_controller_set_control_source()) and
32 * then by having it used by the #GstController or calling
33 * gst_control_source_get_value() or gst_control_source_get_value_array().
35 * For implementing a new #GstControlSource one has to implement a
36 * #GstControlSourceBind method, which will depending on the #GParamSpec set up
37 * the control source for use and sets the #GstControlSourceGetValue and
38 * #GstControlSourceGetValueArray functions. These are then used by
39 * gst_control_source_get_value() or gst_control_source_get_value_array()
40 * to get values for specific timestamps.
44 #include "gst_private.h"
46 #include <glib-object.h>
49 #include "gstcontrolsource.h"
51 #define GST_CAT_DEFAULT control_source_debug
52 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
54 G_DEFINE_ABSTRACT_TYPE (GstControlSource, gst_control_source, G_TYPE_OBJECT);
56 static GObjectClass *parent_class = NULL;
59 gst_control_source_class_init (GstControlSourceClass * klass)
61 //GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
63 parent_class = g_type_class_peek_parent (klass);
65 /* Has to be implemented by children */
68 GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "gstcontrolsource", 0,
69 "dynamic parameter control sources");
73 gst_control_source_init (GstControlSource * self)
75 /* Set default handlers that print a warning */
76 self->get_value = NULL;
77 self->get_value_array = NULL;
82 * gst_control_source_get_value:
83 * @self: the #GstControlSource object
84 * @timestamp: the time for which the value should be returned
87 * Gets the value for this #GstControlSource at a given timestamp.
89 * Returns: FALSE if the value couldn't be returned, TRUE otherwise.
92 gst_control_source_get_value (GstControlSource * self, GstClockTime timestamp,
95 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
97 if (G_LIKELY (self->get_value)) {
98 return self->get_value (self, timestamp, value);
100 GST_ERROR ("Not bound to a specific property yet!");
106 * gst_control_source_get_value_array:
107 * @self: the #GstControlSource object
108 * @timestamp: the time that should be processed
109 * @value_array: array to put control-values in
111 * Gets an array of values for one element property.
113 * All fields of @value_array must be filled correctly. Especially the
114 * @value_array->values array must be big enough to keep the requested amount
117 * The type of the values in the array is the same as the property's type.
119 * Returns: %TRUE if the given array could be filled, %FALSE otherwise
122 gst_control_source_get_value_array (GstControlSource * self,
123 GstClockTime timestamp, GstClockTime interval, guint n_values,
126 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
128 if (G_LIKELY (self->get_value_array)) {
129 return self->get_value_array (self, timestamp, interval, n_values, values);
131 GST_ERROR ("Not bound to a specific property yet!");
137 * gst_control_source_bind:
138 * @self: the #GstControlSource object
139 * @pspec: #GParamSpec for the property for which this #GstControlSource should generate values.
141 * Binds a #GstControlSource to a specific property. This must be called only once for a
144 * Returns: %TRUE if the #GstControlSource was bound correctly, %FALSE otherwise.
147 gst_control_source_bind (GstControlSource * self, GParamSpec * pspec)
149 gboolean ret = FALSE;
151 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
152 g_return_val_if_fail (GST_CONTROL_SOURCE_GET_CLASS (self)->bind, FALSE);
153 g_return_val_if_fail (!self->bound, FALSE);
155 ret = GST_CONTROL_SOURCE_GET_CLASS (self)->bind (self, pspec);