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 controller_debug
52 GST_DEBUG_CATEGORY_EXTERN (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 */
70 gst_control_source_init (GstControlSource * self)
72 /* Set default handlers that print a warning */
73 self->get_value = NULL;
74 self->get_value_array = NULL;
79 * gst_control_source_get_value:
80 * @self: the #GstControlSource object
81 * @timestamp: the time for which the value should be returned
84 * Gets the value for this #GstControlSource at a given timestamp.
86 * Returns: FALSE if the value couldn't be returned, TRUE otherwise.
89 gst_control_source_get_value (GstControlSource * self, GstClockTime timestamp,
92 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
94 if (G_LIKELY (self->get_value)) {
95 return self->get_value (self, timestamp, value);
97 GST_ERROR ("Not bound to a specific property yet!");
103 * gst_control_source_get_value_array:
104 * @self: the #GstControlSource object
105 * @timestamp: the time that should be processed
106 * @value_array: array to put control-values in
108 * Gets an array of values for one element property.
110 * All fields of @value_array must be filled correctly. Especially the
111 * @value_array->values array must be big enough to keep the requested amount
114 * The type of the values in the array is the same as the property's type.
116 * Returns: %TRUE if the given array could be filled, %FALSE otherwise
119 gst_control_source_get_value_array (GstControlSource * self,
120 GstClockTime timestamp, GstValueArray * value_array)
122 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
124 if (G_LIKELY (self->get_value_array)) {
125 return self->get_value_array (self, timestamp, value_array);
127 GST_ERROR ("Not bound to a specific property yet!");
133 * gst_control_source_bind:
134 * @self: the #GstControlSource object
135 * @pspec: #GParamSpec for the property for which this #GstControlSource should generate values.
137 * Binds a #GstControlSource to a specific property. This must be called only once for a
140 * Returns: %TRUE if the #GstControlSource was bound correctly, %FALSE otherwise.
143 gst_control_source_bind (GstControlSource * self, GParamSpec * pspec)
145 gboolean ret = FALSE;
147 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
148 g_return_val_if_fail (GST_CONTROL_SOURCE_GET_CLASS (self)->bind, FALSE);
149 g_return_val_if_fail (!self->bound, FALSE);
151 ret = GST_CONTROL_SOURCE_GET_CLASS (self)->bind (self, pspec);