mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-12-27 10:40:34 +00:00
117 lines
3.1 KiB
Markdown
117 lines
3.1 KiB
Markdown
---
|
|
title: Initializing GStreamer
|
|
...
|
|
|
|
# Initializing GStreamer
|
|
|
|
When writing a GStreamer application, you can simply include `gst/gst.h`
|
|
to get access to the library functions. Besides that, you will also need
|
|
to initialize the GStreamer library.
|
|
|
|
## Simple initialization
|
|
|
|
Before the GStreamer libraries can be used, `gst_init` 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.
|
|
|
|
A typical program \[1\] would have code to initialize GStreamer that
|
|
looks like this:
|
|
|
|
``` c
|
|
|
|
#include <stdio.h>
|
|
#include <gst/gst.h>
|
|
|
|
int
|
|
main (int argc,
|
|
char *argv[])
|
|
{
|
|
const gchar *nano_str;
|
|
guint major, minor, micro, nano;
|
|
|
|
gst_init (&argc, &argv);
|
|
|
|
gst_version (&major, &minor, µ, &nano);
|
|
|
|
if (nano == 1)
|
|
nano_str = "(CVS)";
|
|
else if (nano == 2)
|
|
nano_str = "(Prerelease)";
|
|
else
|
|
nano_str = "";
|
|
|
|
printf ("This program is linked against GStreamer %d.%d.%d %s\n",
|
|
major, minor, micro, nano_str);
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
```
|
|
|
|
Use the `GST_VERSION_MAJOR`, `GST_VERSION_MINOR` and `GST_VERSION_MICRO`
|
|
macros to get the GStreamer version you are building against, or use the
|
|
function `gst_version` 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.
|
|
|
|
It is also possible to call the `gst_init` function with two `NULL`
|
|
arguments, in which case no command line options will be parsed by
|
|
GStreamer.
|
|
|
|
## The GOption interface
|
|
|
|
You can also use a GOption table to initialize your own parameters as
|
|
shown in the next example:
|
|
|
|
``` c
|
|
|
|
#include <gst/gst.h>
|
|
|
|
int
|
|
main (int argc,
|
|
char *argv[])
|
|
{
|
|
gboolean silent = FALSE;
|
|
gchar *savefile = NULL;
|
|
GOptionContext *ctx;
|
|
GError *err = NULL;
|
|
GOptionEntry entries[] = {
|
|
{ "silent", 's', 0, G_OPTION_ARG_NONE, &silent,
|
|
"do not output status information", NULL },
|
|
{ "output", 'o', 0, G_OPTION_ARG_STRING, &savefile,
|
|
"save xml representation of pipeline to FILE and exit", "FILE" },
|
|
{ NULL }
|
|
};
|
|
|
|
ctx = g_option_context_new ("- Your application");
|
|
g_option_context_add_main_entries (ctx, entries, NULL);
|
|
g_option_context_add_group (ctx, gst_init_get_option_group ());
|
|
if (!g_option_context_parse (ctx, &argc, &argv, &err)) {
|
|
g_print ("Failed to initialize: %s\n", err->message);
|
|
g_clear_error (&err);
|
|
g_option_context_free (ctx);
|
|
return 1;
|
|
}
|
|
g_option_context_free (ctx);
|
|
|
|
printf ("Run me with --help to see the Application options appended.\n");
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
```
|
|
|
|
As shown in this fragment, you can use a
|
|
[GOption](http://developer.gnome.org/glib/stable/glib-Commandline-option-parser.html)
|
|
table to define your application-specific command line options, and pass
|
|
this table to the GLib initialization function along with the option
|
|
group returned from the function `gst_init_get_option_group`. Your
|
|
application options will be parsed in addition to the standard GStreamer
|
|
options.
|
|
|
|
1. The code for this example is automatically extracted from the
|
|
documentation and built under `tests/examples/manual` in the
|
|
GStreamer tarball.
|