1 /* GStreamer
2 *
3 * Copyright (C) 2007 Sebastian Dröge <slomo@circular-chaos.org>
4 *
5 * gstcontrolsource.c: Interface declaration for control sources
6 *
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.
11 *
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.
16 *
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.
21 */
22
23 /**
24 * SECTION:gstcontrolsource
25 * @title: GstControlSource
26 * @short_description: base class for control source sources
27 *
28 * The #GstControlSource is a base class for control value sources that could
29 * be used to get timestamp-value pairs. A control source essentially is a
30 * function over time.
31 *
32 * A #GstControlSource is used by first getting an instance of a specific
33 * control-source, creating a binding for the control-source to the target property
34 * of the element and then adding the binding to the element. The binding will
35 * convert the data types and value range to fit to the bound property.
36 *
37 * For implementing a new #GstControlSource one has to implement
38 * #GstControlSourceGetValue and #GstControlSourceGetValueArray functions.
39 * These are then used by gst_control_source_get_value() and
40 * gst_control_source_get_value_array() to get values for specific timestamps.
41 */
42
43 #include "gst_private.h"
44
45 #include <glib-object.h>
46 #include <gst/gst.h>
47
48 #include "gstcontrolsource.h"
49
50 #define GST_CAT_DEFAULT control_source_debug
51 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
52
53 #define _do_init \
54 GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "gstcontrolsource", 0, \
55 "dynamic parameter control sources");
56
57 G_DEFINE_ABSTRACT_TYPE_WITH_CODE (GstControlSource, gst_control_source,
58 GST_TYPE_OBJECT, _do_init);
59
60 static void
gst_control_source_class_init(GstControlSourceClass * klass)61 gst_control_source_class_init (GstControlSourceClass * klass)
62 {
63 }
64
65 static void
gst_control_source_init(GstControlSource * self)66 gst_control_source_init (GstControlSource * self)
67 {
68 self->get_value = NULL;
69 self->get_value_array = NULL;
70 }
71
72 /**
73 * gst_control_source_get_value: (method)
74 * @self: the #GstControlSource object
75 * @timestamp: the time for which the value should be returned
76 * @value: (out): the value
77 *
78 * Gets the value for this #GstControlSource at a given timestamp.
79 *
80 * Returns: %FALSE if the value couldn't be returned, %TRUE otherwise.
81 */
82 gboolean
gst_control_source_get_value(GstControlSource * self,GstClockTime timestamp,gdouble * value)83 gst_control_source_get_value (GstControlSource * self, GstClockTime timestamp,
84 gdouble * value)
85 {
86 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
87 g_return_val_if_fail (GST_CLOCK_TIME_IS_VALID (timestamp), FALSE);
88
89 if (G_LIKELY (self->get_value)) {
90 return self->get_value (self, timestamp, value);
91 } else {
92 GST_ERROR ("Not bound to a specific property yet!");
93 return FALSE;
94 }
95 }
96
97 /**
98 * gst_control_source_get_value_array: (method)
99 * @self: the #GstControlSource object
100 * @timestamp: the first timestamp
101 * @interval: the time steps
102 * @n_values: the number of values to fetch
103 * @values: (array length=n_values): array to put control-values in
104 *
105 * Gets an array of values for for this #GstControlSource. Values that are
106 * undefined contain NANs.
107 *
108 * Returns: %TRUE if the given array could be filled, %FALSE otherwise
109 */
110 gboolean
gst_control_source_get_value_array(GstControlSource * self,GstClockTime timestamp,GstClockTime interval,guint n_values,gdouble * values)111 gst_control_source_get_value_array (GstControlSource * self,
112 GstClockTime timestamp, GstClockTime interval, guint n_values,
113 gdouble * values)
114 {
115 g_return_val_if_fail (GST_IS_CONTROL_SOURCE (self), FALSE);
116 g_return_val_if_fail (GST_CLOCK_TIME_IS_VALID (timestamp), FALSE);
117 g_return_val_if_fail (GST_CLOCK_TIME_IS_VALID (interval), FALSE);
118
119 if (G_LIKELY (self->get_value_array)) {
120 return self->get_value_array (self, timestamp, interval, n_values, values);
121 } else {
122 GST_ERROR ("Not bound to a specific property yet!");
123 return FALSE;
124 }
125 }
126