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>Chapter 9. Building a Test Application</H1
><P
> Often, you will want to test your newly written plugin in an as small
setting as possible. Ususally, <TT
CLASS="filename"
>gst-launch</TT
> is a
good first step at testing a plugin. However, you will often need more
testing features than gst-launch 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
<A
HREF="../manual/index.html"
TARGET="_top"
>Application Development
Manual</A
>.
</P
><P
> At the start, you need to initialize the <SPAN
CLASS="application"
>GStreamer</SPAN
> core library by
calling <CODE
CLASS="function"
>gst_init ()</CODE
>. You can alternatively call
<CODE
CLASS="function"
>gst_init_with_popt_tables ()</CODE
>, which will return
a pointer to popt tables. You can then use libpopt to handle the
given argument table, and this will finish the <SPAN
CLASS="application"
>GStreamer</SPAN
> intialization.
</P
><P
> You can create elements using <CODE
CLASS="function"
>gst_element_factory_make ()</CODE
>,
where the first argument is the element type that you want to create,
and the second argument is a free-form name. The example at the end uses
a simple filesource - decoder - soundcard output pipeline, but you can
use specific debugging elements if that's necessary. For example, an
<CODE
CLASS="classname"
>identity</CODE
> element can be used in the middle of
the pipeline to act as a data-to-application transmitter. This can be
used to check the data for misbehaviours or correctness in your test
application. Also, you can use a <CODE
CLASS="classname"
>fakesink</CODE
>
element at the end of the pipeline to dump your data to the stdout
(in order to do this, set the <CODE
CLASS="function"
>dump</CODE
> property to
TRUE). Lastly, you can use the <CODE
CLASS="classname"
>efence</CODE
> element
(indeed, an eletric fence memory debugger wrapper element) to check
for memory errors.
</P
><P
> During linking, your test application can use fixation or 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.
</P
><P
> Running the pipeline happens through the <CODE
CLASS="function"
>gst_bin_iterate ()</CODE
>
function. Note that during running, you should connect to at least the
<SPAN
CLASS="QUOTE"
>"error"</SPAN
> and <SPAN
CLASS="QUOTE"
>"eos"</SPAN
> signals on the pipeline
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.).
</P
><P
> Never forget to clean up memory in your plugin or your test application.
When going to the NULL state, your element should clean up allocated
memory and caches. Also, it should close down any references held to
possible support libraries. Your application should <CODE
CLASS="function"
>unref ()</CODE
>
the pipeline and make sure it doesn't crash.
</P
><PRE
CLASS="programlisting"
> #include <gst/gst.h>
gint
main (gint arcg,
gchar *argv[])
{
GstElement *pipeline, *filesrc, *decoder, *filter, *sink;
/* initialization */
gst_init (&argc, &argv);
/* create elements */
pipeline = gst_pipeline_new ("my_pipeline");
filesrc = gst_element_factory_make ("filesrc", "my_filesource");
decoder = gst_element_factory_make ("mad", "my_decoder");
filter = gst_element_factory_make ("my_filter", "my_filter");
sink = gst_element_factory_make ("osssink", "audiosink");
g_object_set (G_OBJECT (filesrc), "location", argv[1], NULL);
/* link everything together */
gst_element_link_many (filesrc, decoder, filter, sink, NULL);
gst_bin_add_many (GST_BIN (pipeline), filesrc, decoder, filter, sink, NULL);
/* run */
gst_element_set_state (pipeline, GST_STATE_PLAYING);
while (gst_bin_iterate (GST_BIN (pipeline)));
/* clean up */
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (GST_OBJECT (pipeline));
return 0;
}
</PRE
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