Gstreamer hello world

This example plays a sound file given as parameter with GStreamer. It uses decodebin element so it can play any sound file that can be decoded with installed GStreamer plugins.

#include <gst/gst.h>
#include <glib.h>
 
 
static gboolean
bus_call (GstBus     *bus,
          GstMessage *msg,
          gpointer    data)
{
  GMainLoop *loop = (GMainLoop *) data;
 
  switch (GST_MESSAGE_TYPE (msg)) {
 
    case GST_MESSAGE_EOS:
      g_print ("End of stream\n");
      g_main_loop_quit (loop);
      break;
 
    case GST_MESSAGE_ERROR: {
      gchar  *debug;
      GError *error;
 
      gst_message_parse_error (msg, &error, &debug);
      g_free (debug);
 
      g_printerr ("Error: %s\n", error->message);
      g_error_free (error);
 
      g_main_loop_quit (loop);
      break;
    }
    default:
      break;
  }
 
  return TRUE;
}
 
 
static void
on_pad_added (GstElement *element,
              GstPad     *pad,
              gpointer    data)
{
  GstPad *sinkpad;
  GstElement *decoder = (GstElement *) data;
 
  /* We can now link this pad with the vorbis-decoder sink pad */
  g_print ("Dynamic pad created, linking demuxer/decoder\n");
 
  sinkpad = gst_element_get_static_pad (decoder, "sink");
 
  gst_pad_link (pad, sinkpad);
 
  gst_object_unref (sinkpad);
}
 
 
 
int
main (int   argc,
      char *argv[])
{
  GMainLoop *loop;
 
  GstElement *pipeline, *source, *decoder, *conv, *sink;
  GstBus *bus;
 
  /* Initialisation */
  gst_init (&argc, &argv);
 
  loop = g_main_loop_new (NULL, FALSE);
 
 
  /* Check input arguments */
  if (argc != 2) {
    g_printerr ("Usage: %s <filename>\n", argv[0]);
    return -1;
  }
 
 
  /* Create gstreamer elements */
  pipeline = gst_pipeline_new ("audio-player");
  source   = gst_element_factory_make ("filesrc",       "file-source");
  decoder  = gst_element_factory_make ("decodebin",     "decoder");
  conv     = gst_element_factory_make ("audioconvert",  "converter");
  sink     = gst_element_factory_make ("autoaudiosink", "audio-output");
 
  if (!pipeline || !source || !decoder || !conv || !sink) {
    g_printerr ("One element could not be created. Exiting.\n");
    return -1;
  }
 
  /* Set up the pipeline */
 
  /* we set the input filename to the source element */
  g_object_set (G_OBJECT (source), "location", argv[1], NULL);
 
  /* we add a message handler */
  bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
  gst_bus_add_watch (bus, bus_call, loop);
  gst_object_unref (bus);
 
  /* we add all elements into the pipeline */
  /* file-source | decoder | converter | output */
  gst_bin_add_many (GST_BIN (pipeline),
                    source, decoder, conv, sink, NULL);
 
  /* we link the elements together */
  /* file-source -> decodebin ~> converter -> output */
  gst_element_link (source, decoder);
  gst_element_link_many (conv, sink, NULL);
	/* dynamic linking */
  g_signal_connect (decoder, "pad-added", G_CALLBACK (on_pad_added), conv);
 
  /* Set the pipeline to "playing" state*/
  g_print ("Now playing: %s\n", argv[1]);
  gst_element_set_state (pipeline, GST_STATE_PLAYING);
 
  /* Iterate */
  g_print ("Running...\n");
  g_main_loop_run (loop);
 
  /* Out of the main loop, clean up nicely */
  g_print ("Returned, stopping playback\n");
  gst_element_set_state (pipeline, GST_STATE_NULL);
 
  g_print ("Deleting pipeline\n");
  gst_object_unref (GST_OBJECT (pipeline));
 
  return 0;
}