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., 51 Franklin St, Fifth Floor,
20 * Boston, MA 02110-1301, 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 to get timestamp-value pairs. A control source essentially is a
31 * A #GstControlSource is used by first getting an instance of a specific
32 * control-source, creating a binding for the control-source to the target property
33 * of the element and then adding the binding to the element. The binding will
34 * convert the data types and value range to fit to the bound property.
36 * For implementing a new #GstControlSource one has to implement
37 * #GstControlSourceGetValue and #GstControlSourceGetValueArray functions.
38 * These are then used by gst_control_source_get_value() and
39 * gst_control_source_get_value_array() to get values for specific timestamps.
42 #include "gst_private.h"
44 #include <glib-object.h>
47 #include "gstcontrolsource.h"
49 #define GST_CAT_DEFAULT control_source_debug
50 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
53 GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "gstcontrolsource", 0, \
54 "dynamic parameter control sources");
56 G_DEFINE_ABSTRACT_TYPE_WITH_CODE (GstControlSource, gst_control_source,
57 GST_TYPE_OBJECT, _do_init);
59 static GObject *gst_control_source_constructor (GType type,
60 guint n_construct_params, GObjectConstructParam * construct_params);
63 gst_control_source_class_init (GstControlSourceClass * klass)
65 GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
67 gobject_class->constructor = gst_control_source_constructor;
71 gst_control_source_init (GstControlSource * self)
73 self->get_value = NULL;
74 self->get_value_array = NULL;
78 gst_control_source_constructor (GType type, guint n_construct_params,
79 GObjectConstructParam * construct_params)
84 G_OBJECT_CLASS (gst_control_source_parent_class)->constructor (type,
85 n_construct_params, construct_params);
86 gst_object_ref_sink (self);
92 * gst_control_source_get_value: (method)
93 * @self: the #GstControlSource object
94 * @timestamp: the time for which the value should be returned
95 * @value: (out): the value
97 * Gets the value for this #GstControlSource at a given timestamp.
99 * Returns: %FALSE if the value couldn't be returned, %TRUE otherwise.
102 gst_control_source_get_value (GstControlSource * self, GstClockTime timestamp,
105 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
107 if (G_LIKELY (self->get_value)) {
108 return self->get_value (self, timestamp, value);
110 GST_ERROR ("Not bound to a specific property yet!");
116 * gst_control_source_get_value_array: (method)
117 * @self: the #GstControlSource object
118 * @timestamp: the first timestamp
119 * @interval: the time steps
120 * @n_values: the number of values to fetch
121 * @values: (array length=n_values): array to put control-values in
123 * Gets an array of values for for this #GstControlSource. Values that are
124 * undefined contain NANs.
126 * Returns: %TRUE if the given array could be filled, %FALSE otherwise
129 gst_control_source_get_value_array (GstControlSource * self,
130 GstClockTime timestamp, GstClockTime interval, guint n_values,
133 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
135 if (G_LIKELY (self->get_value_array)) {
136 return self->get_value_array (self, timestamp, interval, n_values, values);
138 GST_ERROR ("Not bound to a specific property yet!");