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eba146a5f4
The URL layout has changed. Fix the links and comment out one paragraph where the doc is gone. Fixes #702135
127 lines
4 KiB
XML
127 lines
4 KiB
XML
<chapter id="chapter-init">
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<title>Initializing &GStreamer;</title>
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<para>
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When writing a &GStreamer; application, you can simply include
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<filename>gst/gst.h</filename> to get access to the library
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functions. Besides that, you will also need to initialize the
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&GStreamer; library.
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</para>
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<sect1 id="section-init-c">
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<title>Simple initialization</title>
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<para>
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Before the &GStreamer; libraries can be used,
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<function>gst_init</function> has to be called from the main
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application. This call will perform the necessary initialization
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of the library as well as parse the &GStreamer;-specific command
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line options.
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</para>
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<para>
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A typical program &EXAFOOT; would have code to initialize
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&GStreamer; that looks like this:
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</para>
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<example id="ex-init-c">
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<title>Initializing GStreamer</title>
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<programlisting>
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<!-- example-begin init.c -->
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#include <stdio.h>
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#include <gst/gst.h>
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int
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main (int argc,
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char *argv[])
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{
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const gchar *nano_str;
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guint major, minor, micro, nano;
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gst_init (&argc, &argv);
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gst_version (&major, &minor, &micro, &nano);
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if (nano == 1)
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nano_str = "(CVS)";
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else if (nano == 2)
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nano_str = "(Prerelease)";
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else
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nano_str = "";
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printf ("This program is linked against GStreamer %d.%d.%d %s\n",
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major, minor, micro, nano_str);
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return 0;
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}
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<!-- example-end init.c -->
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</programlisting>
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</example>
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<para>
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Use the <symbol>GST_VERSION_MAJOR</symbol>,
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<symbol>GST_VERSION_MINOR</symbol> and <symbol>GST_VERSION_MICRO</symbol>
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macros to get the &GStreamer; version you are building against, or
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use the function <function>gst_version</function> to get the version
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your application is linked against. &GStreamer; currently uses a
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scheme where versions with the same major and minor versions are
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API-/ and ABI-compatible.
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</para>
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<para>
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It is also possible to call the <function>gst_init</function> function
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with two <symbol>NULL</symbol> arguments, in which case no command line
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options will be parsed by <application>GStreamer</application>.
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</para>
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</sect1>
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<sect1>
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<title>The GOption interface</title>
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<para>
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You can also use a GOption table to initialize your own parameters as
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shown in the next example:
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</para>
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<example id="ex-goption-c">
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<title>Initialisation using the GOption interface</title>
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<programlisting>
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<!-- example-begin goption.c -->
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#include <gst/gst.h>
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int
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main (int argc,
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char *argv[])
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{
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gboolean silent = FALSE;
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gchar *savefile = NULL;
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GOptionContext *ctx;
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GError *err = NULL;
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GOptionEntry entries[] = {
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{ "silent", 's', 0, G_OPTION_ARG_NONE, &silent,
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"do not output status information", NULL },
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{ "output", 'o', 0, G_OPTION_ARG_STRING, &savefile,
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"save xml representation of pipeline to FILE and exit", "FILE" },
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{ NULL }
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};
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ctx = g_option_context_new ("- Your application");
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g_option_context_add_main_entries (ctx, entries, NULL);
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g_option_context_add_group (ctx, gst_init_get_option_group ());
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if (!g_option_context_parse (ctx, &argc, &argv, &err)) {
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g_print ("Failed to initialize: %s\n", err->message);
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g_error_free (err);
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return 1;
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}
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printf ("Run me with --help to see the Application options appended.\n");
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return 0;
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}
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<!-- example-end goption.c -->
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</programlisting>
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</example>
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<para>
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As shown in this fragment, you can use a <ulink
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url="http://developer.gnome.org/glib/stable/glib-Commandline-option-parser.html"
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type="http">GOption</ulink> table to define your application-specific
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command line options, and pass this table to the GLib initialization
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function along with the option group returned from the
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function <function>gst_init_get_option_group</function>. Your
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application options will be parsed in addition to the standard
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<application>GStreamer</application> options.
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</para>
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</sect1>
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</chapter>
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