reference:
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/x291.html

# ./a.out 
(process:6792): GStreamer-WARNING **: The GStreamer function gst_init_get_option_group() was
        called, but the GLib threading system has not been initialised
        yet, something that must happen before any other GLib function
        is called. The application needs to be fixed so that it calls
           if (!g_thread_supported ()) g_thread_init(NULL);
        as very first thing in its main() function. Please file a bug
        against this application.
Run me with --help to see the Application options appended.



Fix:

  // must initialise the threading system before using any other GLib funtion
  if (!g_thread_supported ())
    g_thread_init (NULL);