Hi I trying to control the position property of a smptealpha element. It controls the opacity of the alpha channel, it varies from 0.0 to 1.0. The duration of this setting is 500ms. I am working around this problem, it happens at runtime, I can't figure out what it's wrong. Thanks and regards, Rossana Here's the code; _____________ gst_interpolation_control_source_set: assertion `G_VALUE_TYPE (value) == self->priv->type' failed // Agrego Controlador gdouble duracion = 500; GstController * ctrl = gst_object_control_properties(G_OBJECT(smpte), "position",NULL); if (ctrl == NULL) { GST_WARNING ("No puede controlar el elemento fuente\n"); return 0; } // Todo valor GValue debe inicializarse en 0 GValue val_double = { 0, }; g_value_init (&val_double, G_TYPE_DOUBLE); // Seteo modo de interpolacion GstInterpolationControlSource * csource = gst_interpolation_control_source_new(); 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, 1.0); gst_interpolation_control_source_set(csource,(duracion*GST_MSECOND),&val_double); gst_controller_set_control_source (ctrl, "position", GST_CONTROL_SOURCE (csource)); g_object_unref (csource); g_value_unset (&val_double);