gst_controller_new returns NULL

[Rossana Guerra]

Hello everyone, I am translating the following code to C/C++:
http://notes.brooks.nu/2011/01/python-gstreamer-controller/
It's a controller for controlling the alpha channel during crossfade, I
adapted it for transitions, using, smpte instead.

The fact is it returns NULL and the programs stop running. The code is
below, I appreciate any suggestion.
I am a bit clueless is an adaptation of a code I did before and it works.

Thanks and regards.

Rossana

//// the code

#include <gst.h>
#include <controller/gstcontroller.h>

#include <iostream>


using namespace std;

// Manejador de errores
static gboolean bus_call (GstBus *bus, GstMessage *msg, gpointer data)
{
::::::::::::::::::::::::................
}

static void on_pad_added (GstElement *element, GstPad *pad, gpointer  data)
{
  GstPad *sinkpad = NULL;
  GstElement * elemento = (GstElement *) data;


  /* Ahora linkeo el pad de comp con sink pad */
  g_print ("Dynamic pad created, linking queue\n");
  sinkpad = gst_element_get_static_pad (elemento, "sink");


  gst_pad_link (pad, sinkpad);
  gst_object_unref(sinkpad);

}


int main(int argc, char *argv[])
{

  GMainLoop *loop = NULL;

  GstElement *src1, *src2,*dec1,*dec2,*alfa1,*color,*smpte,*queue,*sink;
  GstBus *bus;

  gdouble duracion = 500;
  gint transicion = 1;

  cout << "Inicio..." << endl;

    /* init GStreamer */
  gst_init (&argc, &argv);
  gst_controller_init (&argc, &argv);

  loop = g_main_loop_new (NULL, FALSE);

  /* make sure we have input */
  if (argc != 3) {
    g_print ("Usage: %s <filename1> <filename2>\n", argv[0]);
    return -1;
  }

  src1 = gst_element_factory_make("filesrc", "src1");
  g_object_set(G_OBJECT(src1),"location",argv[1], NULL);

  src2 = gst_element_factory_make("filesrc", "src2");
  g_object_set(G_OBJECT(src1),"location",argv[2], NULL);

  GstElement *pipeline = gst_pipeline_new ("video-player");

  dec1 = gst_element_factory_make("decodebin2","dec1");

  dec2 = gst_element_factory_make("decodebin2","dec2");

  bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
  gst_bus_add_watch (bus, bus_call, loop);
  gst_object_unref (bus);

  alfa1   = gst_element_factory_make ("alpha","alfa1");
  smpte  = gst_element_factory_make ("smptealpha","smpte");
  color  = gst_element_factory_make ("ffmpegcolorspace", "color");
  GstElement * mixer  = gst_element_factory_make("videomixer", "mixer");

  if ((!alfa1) || (!smpte) || (!color) || (!mixer))
  {
      g_printerr ("Alguno de los elementos del Bin no pudo ser creado.
Saliendo\n");
     return 0;
  }

  queue = gst_element_factory_make("queue", "queue");
  sink  = gst_element_factory_make("autovideosink", "sink");

  cout << "Creando 1..." << endl;

  // Agrego Controlador

  GstController * ctrl = NULL;
  if (!(ctrl = gst_controller_new (G_OBJECT(smpte), "alpha",NULL)))  ///
Here's the error, always return NULL
  {
        cout << "ctrl value..." << ctrl << endl;
        GST_WARNING ("No puede controlar el elemento fuente\n");
        return 1;
  }

  // Todo valor GValue debe inicializarse en 0
  GValue val_double = { 0, };
  g_value_init (&val_double, G_TYPE_DOUBLE);


  // Creo la fuente al controlador y la asocio al controlador
  // Seteo modo de interpolacion

  GstInterpolationControlSource * csource =
gst_interpolation_control_source_new();
  gst_controller_set_control_source (ctrl, "alpha", GST_CONTROL_SOURCE
(csource));


gst_interpolation_control_source_set_interpolation_mode(csource,GST_INTERPOLATE_LINEAR);

  // Seteo primer valor
  g_value_set_double(&val_double, 0.0);
  gst_interpolation_control_source_set(csource,(0 *
GST_MSECOND),&val_double);

  // Seteo segundo valor
  g_value_set_double (&val_double, duracion);
  gst_interpolation_control_source_set(csource,(1 *
GST_MSECOND),&val_double);

  g_object_unref (csource);

  gst_bin_add_many (GST_BIN (pipeline),src1, src2, dec1, dec2, alfa1, smpte,
mixer, queue, color, sink, NULL);
  g_signal_connect (G_OBJECT (dec1), "pad-added", G_CALLBACK
(on_pad_added),alfa1);
  g_signal_connect (G_OBJECT (dec2), "pad-added", G_CALLBACK
(on_pad_added),smpte);

  gst_element_link (src1,dec1);
  gst_element_link (src2,dec2);
  gst_element_link (alfa1,mixer);
  gst_element_link (smpte,mixer);
  gst_element_link (mixer,queue);
  gst_element_link (queue,sink);
  g_object_set(smpte,"type", transicion, NULL);

  /* now run */
  gst_element_set_state (pipeline, GST_STATE_PLAYING);
  cout << "Playing..." << endl;
  g_main_loop_run (loop);

    /* also clean up */
  gst_element_set_state (pipeline, GST_STATE_NULL);
  gst_object_unref (GST_OBJECT (pipeline));

  return 0;
}
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