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118 lines
3.1 KiB
Markdown
118 lines
3.1 KiB
Markdown
---
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title: Initializing GStreamer
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...
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# Initializing GStreamer
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When writing a GStreamer application, you can simply include `gst/gst.h`
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to get access to the library functions. Besides that, you will also need
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to initialize the GStreamer library.
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## Simple initialization
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Before the GStreamer libraries can be used, `gst_init` has to be called
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from the main application. This call will perform the necessary
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initialization of the library as well as parse the GStreamer-specific
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command line options.
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A typical program \[1\] would have code to initialize GStreamer that
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looks like this:
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``` 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, µ, &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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```
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Use the `GST_VERSION_MAJOR`, `GST_VERSION_MINOR` and `GST_VERSION_MICRO`
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macros to get the GStreamer version you are building against, or use the
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function `gst_version` to get the version your application is linked
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against. GStreamer currently uses a scheme where versions with the same
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major and minor versions are API-/ and ABI-compatible.
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It is also possible to call the `gst_init` function with two `NULL`
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arguments, in which case no command line options will be parsed by
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GStreamer.
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## The GOption interface
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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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``` 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_clear_error (&err);
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g_option_context_free (ctx);
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return 1;
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}
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g_option_context_free (ctx);
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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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```
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As shown in this fragment, you can use a
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[GOption](http://developer.gnome.org/glib/stable/glib-Commandline-option-parser.html)
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table to define your application-specific command line options, and pass
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this table to the GLib initialization function along with the option
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group returned from the function `gst_init_get_option_group`. Your
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application options will be parsed in addition to the standard GStreamer
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options.
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1. The code for this example is automatically extracted from the
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documentation and built under `tests/examples/manual` in the
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GStreamer tarball.
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