Newbie question: Basic Tutorial #3 (Dynamic Pipelines)

[johnnyoo]

Hey there. I go this working. Here is the solution I used.

#include <gst/gst.h>

/* Structure to contain all our information, so we can pass it to callbacks
*/
typedef struct _CustomData {
  GstElement *pipeline;
  GstElement *source;
  GstElement *convert;
  GstElement *sink;
  GstElement *video_convert, *video_sink;//for video
} CustomData;

/* Handler for the pad-added signal */
static void pad_added_handler (GstElement *src, GstPad *pad, CustomData
*data);

int main(int argc, char *argv[]) {
  CustomData data;
  GstBus *bus;
  GstMessage *msg;
  GstStateChangeReturn ret;
  gboolean terminate = FALSE;

  /* Initialize GStreamer */
  gst_init (&argc, &argv);

  /* Create the elements */
  data.source = gst_element_factory_make ("uridecodebin", "source");
  data.convert = gst_element_factory_make ("audioconvert", "convert");
  data.sink = gst_element_factory_make ("autoaudiosink", "sink");
  
  /*
   * Dynamic pad linking has traditionally been a difficult topic for a lot
of programmers. 
   * Prove that you have achieved its mastery by instantiating an
autovideosink (probably with an videoconvert in front) 
   * and link it to the demuxer when the right pad appears.
   * Hint: You are already printing on screen the type of the video pads.
   */

  
  /*
   *  FYI   
   *  
   *  data.video_convert = gst_element_factory_make ("videoconvert",
"convert");
  	  data.video_sink = gst_element_factory_make ("autovideosink", "sink");
   * 
   * 	(john-test:10082): GStreamer-WARNING **: Name 'convert' is not unique
in bin 'test-pipeline', not adding
		(john-test:10082): GStreamer-WARNING **: Name 'sink' is not unique in bin
'test-pipeline', not adding
   * 
   */
  data.video_convert = gst_element_factory_make ("videoconvert",
"vid_convert");
  data.video_sink = gst_element_factory_make ("autovideosink", "vid_sink");

  /* Create the empty pipeline */
  data.pipeline = gst_pipeline_new ("test-pipeline");

  if (!data.pipeline || !data.source || !data.convert || !data.sink ||
!data.video_convert || !data.video_sink) {
      g_printerr ("Not all elements could be created.\n");
      return -1;
    }

  /* Build the pipeline. Note that we are NOT linking the source at this */
  gst_bin_add_many (GST_BIN (data.pipeline), data.source, data.convert,
data.sink, data.video_convert, data.video_sink, NULL);
  if (!gst_element_link (data.convert, data.sink)) {
    g_printerr ("audio Elements could not be linked.\n");
    gst_object_unref (data.pipeline);
    return -1;
  }

  if (!gst_element_link (data.video_convert, data.video_sink)) {
    g_printerr ("video Elements could not be linked.\n");
    gst_object_unref (data.pipeline);
    return -1;
  }
  
  /* Set the URI to play */
  g_object_set (data.source, "uri",
"https://www.freedesktop.org/software/gstreamer-sdk/data/media/sintel_trailer-480p.webm",
NULL);

  /* Connect to the pad-added signal */
  g_signal_connect (data.source, "pad-added", G_CALLBACK
(pad_added_handler), &data);

  /* Start playing */
  ret = gst_element_set_state (data.pipeline, GST_STATE_PLAYING);
  if (ret == GST_STATE_CHANGE_FAILURE) {
    g_printerr ("Unable to set the pipeline to the playing state.\n");
    gst_object_unref (data.pipeline);
    return -1;
  }

  /* Listen to the bus */
  bus = gst_element_get_bus (data.pipeline);
  do {
    msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,
        GST_MESSAGE_STATE_CHANGED | GST_MESSAGE_ERROR | GST_MESSAGE_EOS);

    /* Parse message */
    if (msg != NULL) {
      GError *err;
      gchar *debug_info;

      switch (GST_MESSAGE_TYPE (msg)) {
        case GST_MESSAGE_ERROR:
          gst_message_parse_error (msg, &err, &debug_info);
          g_printerr ("Error received from element %s: %s\n",
GST_OBJECT_NAME (msg->src), err->message);
          g_printerr ("Debugging information: %s\n", debug_info ? debug_info
: "none");
          g_clear_error (&err);
          g_free (debug_info);
          terminate = TRUE;
          break;
        case GST_MESSAGE_EOS:
          g_print ("End-Of-Stream reached.\n");
          terminate = TRUE;
          break;
        case GST_MESSAGE_STATE_CHANGED:
          /* We are only interested in state-changed messages from the
pipeline */
          if (GST_MESSAGE_SRC (msg) == GST_OBJECT (data.pipeline)) {
            GstState old_state, new_state, pending_state;
            gst_message_parse_state_changed (msg, &old_state, &new_state,
&pending_state);
            g_print ("Pipeline state changed from %s to %s:\n",
                gst_element_state_get_name (old_state),
gst_element_state_get_name (new_state));
          }
          break;
        default:
          /* We should not reach here */
          g_printerr ("Unexpected message received.\n");
          break;
      }
      gst_message_unref (msg);
    }
  } while (!terminate);

  /* Free resources */
  gst_object_unref (bus);
  gst_element_set_state (data.pipeline, GST_STATE_NULL);
  gst_object_unref (data.pipeline);
  return 0;
}

/* This function will be called by the pad-added signal */
static void pad_added_handler (GstElement *src, GstPad *new_pad, CustomData
*data) {
  
  GstPad *sink_pad = NULL;
  
  GstPadLinkReturn ret;
  GstCaps *new_pad_caps = NULL;
  GstStructure *new_pad_struct = NULL;
  const gchar *new_pad_type = NULL;

  g_print ("Received new pad '%s' from '%s':\n", GST_PAD_NAME (new_pad),
GST_ELEMENT_NAME (src));
  
  /* Check the new pad's type */
  new_pad_caps = gst_pad_get_current_caps (new_pad);
  new_pad_struct = gst_caps_get_structure (new_pad_caps, 0);
  new_pad_type = gst_structure_get_name (new_pad_struct);
  
  if (g_str_has_prefix (new_pad_type, "audio/x-raw")) {
	  g_print ("init audio GstPad\n");
	  sink_pad = gst_element_get_static_pad (data->convert, "sink");
  }
  else if(g_str_has_prefix (new_pad_type, "video/x-raw")) {
	  g_print ("init video GstPad\n");
	  sink_pad = gst_element_get_static_pad (data->video_convert, "sink");
  } else {
	  g_print ("It has type '%s' which is not raw audio or video. Ignoring.\n",
new_pad_type);
	  goto exit;
  }
  
  /* If our converter is already linked, we have nothing to do here */
  if (gst_pad_is_linked (sink_pad)) {
    g_print ("We are already linked. Ignoring.\n");
    goto exit;
  }

  /* Attempt the link */
  ret = gst_pad_link (new_pad, sink_pad);
  if (GST_PAD_LINK_FAILED (ret)) {
    g_print ("Type is '%s' but link failed for reason '%i'.\n",
new_pad_type, ret);
  } else {
    g_print ("Link succeeded (type '%s').\n", new_pad_type);
  }

exit:
  /* Unreference the new pad's caps, if we got them */
  if (new_pad_caps != NULL)
    gst_caps_unref (new_pad_caps);

  /* Unreference the sink pad */
  gst_object_unref (sink_pad);
}




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