<!-- ############ chapter ############# -->
-<chapter id="chapter-building-args" xreflabel="Adding Arguments">
- <title>Adding Arguments</title>
+<chapter id="chapter-building-args" xreflabel="Adding Properties">
+ <title>Adding Properties</title>
<para>
The primary and most important way of controlling how an element behaves,
is through GObject properties. GObject properties are defined in the
and can then fill in the value or take action required for that property
to change value internally.
</para>
+ <para>
+ You probably also want to keep an instance variable around
+ with the currently configured value of the property that you use in the
+ get and set functions.
+ Note that <classname>GObject</classname> will not automatically set your
+ instance variable to the default value, you will have to do that in the
+ <function>_init ()</function> function of your element.
+ </para>
<programlisting><!-- example-begin properties.c a --><!--
#include "filter.h"
GST_BOILERPLATE (GstMyFilter, gst_my_filter, GstElement, GST_TYPE_ELEMENT);
<!-- example-begin properties.c b -->
/* properties */
enum {
- ARG_0,
- ARG_SILENT
+ PROP_0,
+ PROP_SILENT
/* FILL ME */
};
{
GObjectClass *object_class = G_OBJECT_CLASS (klass);
+ /* define virtual function pointers */
+ object_class->set_property = gst_my_filter_set_property;
+ object_class->get_property = gst_my_filter_get_property;
+
/* define properties */
- g_object_class_install_property (object_class, ARG_SILENT,
+ g_object_class_install_property (object_class, PROP_SILENT,
g_param_spec_boolean ("silent", "Silent",
"Whether to be very verbose or not",
FALSE, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
-
- /* define virtual function pointers */
- object_class->set_property = gst_my_filter_set_property;
- object_class->get_property = gst_my_filter_get_property;
}
static void
GstMyFilter *filter = GST_MY_FILTER (object);
switch (prop_id) {
- case ARG_SILENT:
+ case PROP_SILENT:
filter->silent = g_value_get_boolean (value);
g_print ("Silent argument was changed to %s\n",
filter->silent ? "true" : "false");
GstMyFilter *filter = GST_MY_FILTER (object);
switch (prop_id) {
- case ARG_SILENT:
+ case PROP_SILENT:
g_value_set_boolean (value, filter->silent);
break;
default:
#include "register.func"
--><!-- example-end properties.c c --></programlisting>
<para>
- The above is a very simple example of how arguments are used. Graphical
- applications - for example GStreamer Editor - will use these properties
- and will display a user-controllable widget with which these properties
- can be changed. This means that - for the property to be as user-friendly
+ The above is a very simple example of how properties are used. Graphical
+ applications will use these properties and will display a
+ user-controllable widget with which these properties can be changed.
+ This means that - for the property to be as user-friendly
as possible - you should be as exact as possible in the definition of the
property. Not only in defining ranges in between which valid properties
can be located (for integers, floats, etc.), but also in using very
gst_videotestsrc_class_init (GstvideotestsrcClass *klass)
{
[..]
- g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_TYPE,
+ g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_PATTERN,
g_param_spec_enum ("pattern", "Pattern",
"Type of test pattern to generate",
- GST_TYPE_VIDEOTESTSRC_PATTERN, 1, G_PARAM_READWRITE |
- G_PARAM_STATIC_STRINGS));
+ GST_TYPE_VIDEOTESTSRC_PATTERN, GST_VIDEOTESTSRC_SMPTE,
+ G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
[..]
}
</programlisting>
<title>Building a Test Application</title>
<para>
Often, you will want to test your newly written plugin in an as small
- setting as possible. Usually, <filename>gst-launch</filename> is a
+ setting as possible. Usually, <filename>gst-launch-1.0</filename> is a
good first step at testing a plugin. If you have not installed your
plugin in a directory that GStreamer searches, then you will need to
set the plugin path. Either set GST_PLUGIN_PATH to the directory
If you based your plugin off of the gst-plugin template, then this
will look something like
<command>
- gst-launch --gst-plugin-path=$HOME/gst-template/gst-plugin/src/.libs TESTPIPELINE
+ gst-launch-1.0 --gst-plugin-path=$HOME/gst-template/gst-plugin/src/.libs TESTPIPELINE
</command>
However, you will often need more
- testing features than gst-launch can provide, such as seeking, events,
+ testing features than gst-launch-1.0 can provide, such as seeking, events,
interactivity and more. Writing your own small testing program is the
easiest way to accomplish this. This section explains - in a few words
- how to do that. For a complete application development guide, see the
<para>
At the start, you need to initialize the &GStreamer; core library by
calling <function>gst_init ()</function>. You can alternatively call
- <function>gst_init_with_popt_tables ()</function>, which will return
- a pointer to popt tables. You can then use libpopt to handle the
- given argument table, and this will finish the &GStreamer; initialization.
+ <function>gst_init_get_option_group ()</function>, which will return
+ a pointer to GOptionGroup. You can then use GOption to handle the
+ initialization, and this will finish the &GStreamer; initialization.
</para>
<para>
application. Also, you can use a <classname>fakesink</classname>
element at the end of the pipeline to dump your data to the stdout
(in order to do this, set the <function>dump</function> property to
- TRUE). Lastly, you can use the <classname>efence</classname> element
- (indeed, an eletric fence memory debugger wrapper element) to check
- for memory errors.
+ TRUE). Lastly, you can use valgrind to check for memory errors.
</para>
<para>
- During linking, your test application can use fixation or filtered caps
+ During linking, your test application can use filtered caps
as a way to drive a specific type of data to or from your element. This
is a very simple and effective way of checking multiple types of input
and output in your element.
</para>
<para>
- Running the pipeline happens through the <function>gst_bin_iterate ()</function>
- function. Note that during running, you should connect to at least the
- <quote>error</quote> and <quote>eos</quote> signals on the pipeline
+ Note that during running, you should listen for at least the
+ <quote>error</quote> and <quote>eos</quote> messages on the bus
and/or your plugin/element to check for correct handling of this. Also,
you should add events into the pipeline and make sure your plugin handles
these correctly (with respect to clocking, internal caching, etc.).
GstElement *convert1, *convert2, *resample;
GMainLoop *loop;
GstBus *bus;
+ guint watch_id;
/* initialization */
gst_init (&argc, &argv);
/* watch for messages on the pipeline's bus (note that this will only
* work like this when a GLib main loop is running) */
bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
- gst_bus_add_watch (bus, bus_call, loop);
+ watch_id = gst_bus_add_watch (bus, bus_call, loop);
gst_object_unref (bus);
filesrc = gst_element_factory_make ("filesrc", "my_filesource");
* depending on the environment (output used, sound card, driver etc.) */
convert2 = gst_element_factory_make ("audioconvert", "audioconvert2");
resample = gst_element_factory_make ("audioresample", "audioresample");
- sink = gst_element_factory_make ("osssink", "audiosink");
+ sink = gst_element_factory_make ("pulsesink", "audiosink");
if (!sink || !decoder) {
g_print ("Decoder or output could not be found - check your install\n");
return -1;
} else if (!filter) {
g_print ("Your self-written filter could not be found. Make sure it "
- "is installed correctly in $(libdir)/gstreamer-0.10/ or "
- "~/.gstreamer-0.10/plugins/ and that gst-inspect-0.10 lists it. "
- "If it doesn't, check with 'GST_DEBUG=*:2 gst-inspect-0.10' for "
+ "is installed correctly in $(libdir)/gstreamer-1.0/ or "
+ "~/.gstreamer-1.0/plugins/ and that gst-inspect-1.0 lists it. "
+ "If it doesn't, check with 'GST_DEBUG=*:2 gst-inspect-1.0' for "
"the reason why it is not being loaded.");
return -1;
}
/* clean up */
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (pipeline);
+ g_source_remove (watch_id);
+ g_main_loop_unref (loop);
return 0;
}
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