## Gstreamer

Gstreamer — Media library supporting arbitrary formats and filter graphs.

## Synopsis

    #include <gst/gst.h>

    void        gst_init                        (int *argc,
                                                 char **argv[]);
    gboolean    gst_init_with_popt_table        (int *argc,
                                                 char **argv[],
                                                 const struct poptOption *popt_options);
    gboolean    gst_init_check                  (int *argc,
                                                 char **argv[]);
    poptOption* gst_init_get_popt_table         (void);
    void        gst_version                     (guint *major,
                                                 guint *minor,
                                                 guint *micro);
    void        gst_main                        (void);
    void        gst_main_quit                   (void);
    gboolean    gst_has_threads                 (void);
    void        gst_use_threads                 (gboolean use_threads);
    extern      const char             *g_log_domain_gstreamer;
    #define     GST_VERSION_MAJOR
    #define     GST_VERSION_MINOR
    #define     GST_VERSION_MICRO

## Description

GStreamer is a framework for constructing graphs of various filters (termed elements here) that will handle streaming media. Any discreet (packetizable) media type is supported, with provisions for automatically determining source type. Formatting/framing information is provided with a powerful negotiation framework. Plugins are heavily used to provide for all elements, allowing one to construct plugins outside of the GST library, even released binary-only if license require (please don't).

GStreamer borrows heavily from both the OGI media pipeline and Microsoft's DirectShow, hopefully taking the best of both and leaving the cruft behind. Its interface is still very fluid and thus can be changed to increase the sanity/noise ratio.

The GStreamer library should be initialized with gst_init() before it can be used. You should pass a pointer to the main argc and argv variables so that GStreamer can process its own command line options, as shown in the following example.

      int
      main (int argc, char *argv[])
      {
        /* initialize the GStreamer library */
        gst_init (&argc, &argv);
        ...
      }

It's allowed to pass two NULL pointers to gst_init() in case you don't want to pass the command line args to GStreamer.

You can also use a popt table to initialize your own parameters as shown in the next code fragment:

      static gboolean stats = FALSE;
      ...

      int
      main (int argc, char *argv[])
      {
        struct poptOption options[] = {
          { "stats",  's',  POPT_ARG_NONE|POPT_ARGFLAG_STRIP,   &stats,   0,
              "Show pad stats", NULL},
            POPT_TABLEEND
          };

        /* initialize the GStreamer library */
        gst_init_with_popt_table (&argc, &argv, options);

        ...
      }

Use gst_version() to query the library version at runtime or use the GST_VERSION_* macros to find the version at compile time.

gst_main() and gst_main_quit() enter and exit the main loop. GStreamer doesn't currently require you to us a mainloop but can intergrate with it without problems.

## Details

### gst_init ()

    void        gst_init                        (int *argc,
                                                 char **argv[]);

Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.

This function will terminate your program if it was unable to initialize GStreamer for some reason. If you want your program to fall back, use gst_init_check() instead.

`argc` : | pointer to application's argc
`argv` : | pointer to application's argv

### gst_init_with_popt_table ()

    gboolean    gst_init_with_popt_table        (int *argc,
                                                 char **argv[],
                                                 const struct poptOption *popt_options);

Initializes the GStreamer library, parsing the options, setting up internal path lists, registering built-in elements, and loading standard plugins.

`argc` : | pointer to application's argc
`argv` : | pointer to application's argv
`popt_options` : | pointer to a popt table to append
Returns : | TRUE when the initialization succeeded.

### gst_init_check ()

    gboolean    gst_init_check                  (int *argc,
                                                 char **argv[]);

Initializes the GStreamer library, setting up internal path lists, registering built-in elements, and loading standard plugins.

This function will return `FALSE` if GStreamer could not be initialized for some reason. If you want your program to fail fatally, use gst_init() instead.

`argc` : | pointer to application's argc
`argv` : | pointer to application's argv
Returns : | TRUE if GStreamer coul be initialized

### gst_init_get_popt_table ()

    poptOption* gst_init_get_popt_table         (void);

Returns a popt option table with GStreamer's argument specifications. The table is set up to use popt's callback method, so whenever the parsing is actually performed (via a poptGetContext()), the GStreamer libraries will be initialized.

Returns : | a pointer to the static GStreamer option table. No free is necessary.

### gst_version ()

    void        gst_version                     (guint *major,
                                                 guint *minor,
                                                 guint *micro);

Gets the version number of the GStreamer library

`major` : | pointer to a guint to store the major version number
`minor` : | pointer to a guint to store the minor version number
`micro` : | pointer to a guint to store the micro version number

### gst_main ()

    void        gst_main                        (void);

Enter the main GStreamer processing loop

### gst_main_quit ()

    void        gst_main_quit                   (void);

Exits the main GStreamer processing loop

### gst_has_threads ()

    gboolean    gst_has_threads                 (void);

Query if GStreamer has threads enabled.

Returns : | TRUE if threads are enabled.

### gst_use_threads ()

    void        gst_use_threads                 (gboolean use_threads);

Instructs the core to turn on/off threading. When threading is turned off, all thread operations such as mutexes and conditionals are turned into NOPs. use this if you want absolute minimal overhead and you don't use any threads in the pipeline.

`use_threads` : | flag indicating threads should be used

### g_log_domain_gstreamer

    extern const char             *g_log_domain_gstreamer;

The variable that holds the GStreamer log domain

### GST_VERSION_MAJOR

    #define GST_VERSION_MAJOR 0

The major version of GStreamer at compile time

### GST_VERSION_MINOR

    #define GST_VERSION_MINOR 6

The minor version of GStreamer at compile time

### GST_VERSION_MICRO

    #define GST_VERSION_MICRO 5

The micro version of GStreamer at compile time

## See Also

Check out both OGI's pipeline and Microsoft's DirectShow for some background.