source: trunk/third/gstreamer/docs/manual/basics-init.xml @ 21448

<chapter id="chapter-init">
  <title>Initializing &GStreamer;</title>
  <para> 
    When writing a &GStreamer; application, you can simply include
    <filename>gst/gst.h</filename> to get access to the library
    functions. Besides that, you will also need to intialize the
    &GStreamer; library.
  </para>

  <sect1 id="section-init-c">
    <title>Simple initialization</title>
    <para>
      Before the &GStreamer; libraries can be used,
      <function>gst_init</function> has to be called from the main
      application. This call will perform the necessary initialization
      of the library as well as parse the &GStreamer;-specific command
      line options.
    </para>
    <para> 
      A typical program &EXAFOOT; would have code to initialize
      &GStreamer; that looks like this:
    </para>
    <programlisting>
<!-- example-begin init.c -->
#include &lt;gst/gst.h&gt;

int
main (int   argc,
      char *argv[])
{
  guint major, minor, micro;

  gst_init (&amp;argc, &amp;argv);

  gst_version (&amp;major, &amp;minor, &amp;micro);
  printf ("This program is linked against GStreamer %d.%d.%d\n",
          major, minor, micro);

  return 0;
}
<!-- example-end init.c -->
    </programlisting>
    <para>
      Use the <symbol>GST_VERSION_MAJOR</symbol>,
      <symbol>GST_VERSION_MINOR</symbol> and <symbol>GST_VERSION_MICRO</symbol>
      macros to get the &GStreamer; version you are building against, or
      use the function <function>gst_version</function> to get the version
      your application is linked against. &GStreamer; currently uses a
      scheme where versions with the same major and minor versions are
      API-/ and ABI-compatible.
    </para>
    <para>
      It is also possible to call the <function>gst_init</function> function
      with two <symbol>NULL</symbol> arguments, in which case no command line
      options will be parsed by <application>GStreamer</application>.
    </para>
  </sect1>

  <sect1>
    <title>The popt interface</title>
    <para>
      You can also use a popt table to initialize your own parameters as
      shown in the next example:
    </para>
    <programlisting>
<!-- example-begin popt.c -->
#include &lt;gst/gst.h&gt;

int
main (int   argc,
      char *argv[])
{
  gboolean silent = FALSE;
  gchar *savefile = NULL;
  struct poptOption options[] = {
    {"silent",  's',  POPT_ARG_NONE|POPT_ARGFLAG_STRIP,   &amp;silent,   0,
     "do not output status information", NULL},
    {"output",  'o',  POPT_ARG_STRING|POPT_ARGFLAG_STRIP, &amp;savefile, 0,
     "save xml representation of pipeline to FILE and exit", "FILE"},
    POPT_TABLEEND
  };

  gst_init_with_popt_table (&amp;argc, &amp;argv, options);

  printf ("Run me with --help to see the Application options appended.\n");

  return 0;
}
<!-- example-end popt.c -->
    </programlisting>
    <para>
      As shown in this fragment, you can use a <ulink
      url="http://developer.gnome.org/doc/guides/popt/"
      type="http">popt</ulink> table to define your application-specific
      command line options, and pass this table to the
      function <function>gst_init_with_popt_table</function>. Your
      application options will be parsed in addition to the standard
      <application>GStreamer</application> options.
    </para>
  </sect1>
</chapter>