gstreamer/gst/gstelement.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gstelement.c: The base element, all elements derive from this
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/* #define GST_DEBUG_ENABLED */
#include <glib.h>
#include <stdarg.h>
#include <gobject/gvaluecollector.h>
#include "gst_private.h"

#include "gstelement.h"
#include "gstbin.h"
#include "gstscheduler.h"
#include "gstevent.h"
#include "gstutils.h"
#include "gstlog.h"

/* Element signals and args */
enum {
  STATE_CHANGE,
  NEW_PAD,
  PAD_REMOVED,
  ERROR,
  EOS,
  LAST_SIGNAL
};

enum {
  ARG_0,
  /* FILL ME */
};

static void			gst_element_class_init		(GstElementClass *klass);
static void			gst_element_init		(GstElement *element);
static void			gst_element_base_class_init	(GstElementClass *klass);

static void			gst_element_real_set_property	(GObject *object, guint prop_id, 
								 const GValue *value, GParamSpec *pspec);
static void			gst_element_real_get_property	(GObject *object, guint prop_id, GValue *value, 
								 GParamSpec *pspec);

static void 			gst_element_dispose 		(GObject *object);

static GstElementStateReturn	gst_element_change_state	(GstElement *element);
static void			gst_element_error_func		(GstElement* element, GstElement *source, gchar *errormsg);

#ifndef GST_DISABLE_LOADSAVE
static xmlNodePtr		gst_element_save_thyself	(GstObject *object, xmlNodePtr parent);
static void			gst_element_restore_thyself 	(GstObject *parent, xmlNodePtr self);
#endif

GType _gst_element_type = 0;

static GstObjectClass *parent_class = NULL;
static guint gst_element_signals[LAST_SIGNAL] = { 0 };

GType gst_element_get_type (void) 
{
  if (!_gst_element_type) {
    static const GTypeInfo element_info = {
      sizeof(GstElementClass),
      (GBaseInitFunc)gst_element_base_class_init,
      NULL,
      (GClassInitFunc)gst_element_class_init,
      NULL,
      NULL,
      sizeof(GstElement),
      0,
      (GInstanceInitFunc)gst_element_init,
      NULL
    };
    _gst_element_type = g_type_register_static(GST_TYPE_OBJECT, "GstElement", 
		          &element_info, G_TYPE_FLAG_ABSTRACT);
  }
  return _gst_element_type;
}

static void
gst_element_class_init (GstElementClass *klass)
{
  GObjectClass *gobject_class;
  GstObjectClass *gstobject_class;

  gobject_class = (GObjectClass*) klass;
  gstobject_class = (GstObjectClass*) klass;

  parent_class = g_type_class_ref(GST_TYPE_OBJECT);

  gst_element_signals[STATE_CHANGE] =
    g_signal_new ("state_change", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, state_change), NULL, NULL,
		  gst_marshal_VOID__INT_INT, G_TYPE_NONE, 2,
                  G_TYPE_INT, G_TYPE_INT);
  gst_element_signals[NEW_PAD] =
    g_signal_new ("new_pad", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, new_pad), NULL, NULL,
                  gst_marshal_VOID__OBJECT, G_TYPE_NONE, 1,
                  G_TYPE_OBJECT);
  gst_element_signals[PAD_REMOVED] =
    g_signal_new ("pad_removed", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, pad_removed), NULL, NULL,
                  gst_marshal_VOID__OBJECT, G_TYPE_NONE, 1,
                  G_TYPE_OBJECT);
  gst_element_signals[ERROR] =
    g_signal_new ("error", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass, error), NULL, NULL,
                  gst_marshal_VOID__OBJECT_STRING, G_TYPE_NONE, 2,
                  G_TYPE_OBJECT, G_TYPE_STRING);
  gst_element_signals[EOS] =
    g_signal_new ("eos", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstElementClass,eos), NULL, NULL,
                  gst_marshal_VOID__VOID, G_TYPE_NONE, 0);

  gobject_class->set_property 		= GST_DEBUG_FUNCPTR (gst_element_real_set_property);
  gobject_class->get_property 		= GST_DEBUG_FUNCPTR (gst_element_real_get_property);

  gobject_class->dispose 		= GST_DEBUG_FUNCPTR (gst_element_dispose);

#ifndef GST_DISABLE_LOADSAVE
  gstobject_class->save_thyself 	= GST_DEBUG_FUNCPTR (gst_element_save_thyself);
  gstobject_class->restore_thyself 	= GST_DEBUG_FUNCPTR (gst_element_restore_thyself);
#endif

  klass->change_state 			= GST_DEBUG_FUNCPTR (gst_element_change_state);
  klass->error	 			= GST_DEBUG_FUNCPTR (gst_element_error_func);
  klass->elementfactory 		= NULL;
  klass->padtemplates 			= NULL;
  klass->numpadtemplates 		= 0;
}

static void
gst_element_base_class_init (GstElementClass *klass)
{
  GObjectClass *gobject_class;

  gobject_class = (GObjectClass*) klass;

  gobject_class->set_property =		GST_DEBUG_FUNCPTR(gst_element_real_set_property);
  gobject_class->get_property =		GST_DEBUG_FUNCPTR(gst_element_real_get_property);
}

static void
gst_element_init (GstElement *element)
{
  element->current_state = GST_STATE_NULL;
  element->pending_state = GST_STATE_VOID_PENDING;
  element->numpads = 0;
  element->numsrcpads = 0;
  element->numsinkpads = 0;
  element->pads = NULL;
  element->loopfunc = NULL;
  element->sched = NULL;
  element->clock = NULL;
  element->sched_private = NULL;
  element->state_mutex = g_mutex_new ();
  element->state_cond = g_cond_new ();
}

static void
gst_element_real_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
{
  GstElementClass *oclass = GST_ELEMENT_GET_CLASS (object);

  if (oclass->set_property)
    (oclass->set_property) (object, prop_id, value, pspec);
}

static void
gst_element_real_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
{
  GstElementClass *oclass = GST_ELEMENT_GET_CLASS (object);

  if (oclass->get_property)
    (oclass->get_property) (object, prop_id, value, pspec);
}

/** 
 * gst_element_default_error:
 * @object: a #GObject that signalled the error.
 * @orig: the #GstObject that initiated the error.
 * @error: the error message.
 *
 * Adds a default error signal callback to an
 * element. The user data passed to the g_signal_connect is
 * ignored.
 * The default handler will simply print the error string 
 * using g_print.
 */
void
gst_element_default_error (GObject *object, GstObject *orig, gchar *error)
{ 
  gchar *name = gst_object_get_path_string (orig);
  g_print ("ERROR: %s: %s\n", name, error);
  g_free (name);
} 

typedef struct {
  const GParamSpec *pspec;
  GValue value;
} prop_value_t;

static void
element_set_property (GstElement *element, const GParamSpec *pspec, const GValue *value)
{
  prop_value_t *prop_value = g_new0 (prop_value_t, 1);

  prop_value->pspec = pspec;
  prop_value->value = *value;

  g_async_queue_push (element->prop_value_queue, prop_value);
}

static void
element_get_property (GstElement *element, const GParamSpec *pspec, GValue *value)
{
  g_mutex_lock (element->property_mutex);
  g_object_get_property ((GObject*)element, pspec->name, value);
  g_mutex_unlock (element->property_mutex);
}

static void
gst_element_threadsafe_properties_pre_run (GstElement *element)
{
  GST_DEBUG (GST_CAT_THREAD, "locking element %s", GST_OBJECT_NAME (element));
  g_mutex_lock (element->property_mutex);
  gst_element_set_pending_properties (element);
}

static void
gst_element_threadsafe_properties_post_run (GstElement *element)
{
  GST_DEBUG (GST_CAT_THREAD, "unlocking element %s", GST_OBJECT_NAME (element));
  g_mutex_unlock (element->property_mutex);
}

/**
 * gst_element_enable_threadsafe_properties:
 * @element: a #GstElement to enable threadsafe properties on.
 *
 * Installs an asynchronous queue, a mutex and pre- and post-run functions on
 * this element so that properties on the element can be set in a 
 * threadsafe way.
 */
void
gst_element_enable_threadsafe_properties (GstElement *element)
{
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  GST_FLAG_SET (element, GST_ELEMENT_USE_THREADSAFE_PROPERTIES);
  element->pre_run_func = gst_element_threadsafe_properties_pre_run;
  element->post_run_func = gst_element_threadsafe_properties_post_run;
  if (!element->prop_value_queue)
    element->prop_value_queue = g_async_queue_new ();
  if (!element->property_mutex)
    element->property_mutex = g_mutex_new ();
}

/**
 * gst_element_disable_threadsafe_properties:
 * @element: a #GstElement to disable threadsafe properties on.
 *
 * Removes the threadsafe properties, post- and pre-run locks from
 * this element.
 */
void
gst_element_disable_threadsafe_properties (GstElement *element)
{
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  GST_FLAG_UNSET (element, GST_ELEMENT_USE_THREADSAFE_PROPERTIES);
  element->pre_run_func = NULL;
  element->post_run_func = NULL;
  /* let's keep around that async queue */
}

/**
 * gst_element_set_pending_properties:
 * @element: a #GstElement to set the pending properties on.
 *
 * Sets all pending properties on the threadsafe properties enabled
 * element.
 */
void
gst_element_set_pending_properties (GstElement *element) 
{
  prop_value_t *prop_value;

  while ((prop_value = g_async_queue_try_pop (element->prop_value_queue))) {
    g_object_set_property ((GObject*)element, prop_value->pspec->name, &prop_value->value);
    g_value_unset (&prop_value->value);
    g_free (prop_value);
  }
}

/* following 6 functions taken mostly from gobject.c */

/**
 * gst_element_set:
 * @element: a #GstElement to set properties on.
 * @first_property_name: the first property to set.
 * @...: value of the first property, and more properties to set, ending
 *       with NULL.
 *
 * Sets properties on an element. If the element uses threadsafe properties,
 * they will be queued and set on the object when it is scheduled again.
 */
void
gst_element_set (GstElement *element, const gchar *first_property_name, ...)
{
  va_list var_args;
  
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  va_start (var_args, first_property_name);
  gst_element_set_valist (element, first_property_name, var_args);
  va_end (var_args);
}

/**
 * gst_element_get:
 * @element: a #GstElement to get properties of.
 * @first_property_name: the first property to get.
 * @...: pointer to a variable to store the first property in, as well as 
 * more properties to get, ending with NULL.
 *
 * Gets properties from an element. If the element uses threadsafe properties,
 * the element will be locked before getting the given properties.
 */
void
gst_element_get (GstElement *element, const gchar *first_property_name, ...)
{
  va_list var_args;
  
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  va_start (var_args, first_property_name);
  gst_element_get_valist (element, first_property_name, var_args);
  va_end (var_args);
}

/**
 * gst_element_set_valist:
 * @element: a #GstElement to set properties on.
 * @first_property_name: the first property to set.
 * @var_args: the var_args list of other properties to get.
 *
 * Sets properties on an element. If the element uses threadsafe properties,
 * the property change will be put on the async queue.
 */
void
gst_element_set_valist (GstElement *element, const gchar *first_property_name, va_list var_args)
{
  const gchar *name;
  GObject *object;
  
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  object = (GObject *) element;

  GST_DEBUG (GST_CAT_PROPERTIES, 
	     "setting valist of properties starting with %s on element %s",
	     first_property_name, gst_element_get_name (element));

  if (!GST_FLAG_IS_SET (element, GST_ELEMENT_USE_THREADSAFE_PROPERTIES)) {
    g_object_set_valist (object, first_property_name, var_args);
    return;
  }

  g_object_ref (object);
  
  name = first_property_name;

  while (name)
    {
      GValue value = { 0, };
      GParamSpec *pspec;
      gchar *error = NULL;
      
      pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (object), name);

      if (!pspec)
        {
	  g_warning ("%s: object class `%s' has no property named `%s'",
		     G_STRLOC,
		     G_OBJECT_TYPE_NAME (object),
		     name);
	  break;
	}
      if (!(pspec->flags & G_PARAM_WRITABLE))
	{
	  g_warning ("%s: property `%s' of object class `%s' is not writable",
		     G_STRLOC,
		     pspec->name,
		     G_OBJECT_TYPE_NAME (object));
	  break;
	}
      
      g_value_init (&value, G_PARAM_SPEC_VALUE_TYPE (pspec));
      
      G_VALUE_COLLECT (&value, var_args, 0, &error);
      if (error)
	{
	  g_warning ("%s: %s", G_STRLOC, error);
	  g_free (error);
	  
	  /* we purposely leak the value here, it might not be
	   * in a sane state if an error condition occoured
	   */
	  break;
	}
      
      element_set_property (element, pspec, &value);
      g_value_unset (&value);
      
      name = va_arg (var_args, gchar*);
    }

  g_object_unref (object);
}

/**
 * gst_element_get_valist:
 * @element: a #GstElement to get properties of.
 * @first_property_name: the first property to get.
 * @var_args: the var_args list of other properties to get.
 *
 * Gets properties from an element. If the element uses threadsafe properties,
 * the element will be locked before getting the given properties.
 */
void
gst_element_get_valist (GstElement *element, const gchar *first_property_name, va_list var_args)
{
  const gchar *name;
  GObject *object;
  
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  object = (GObject*)element;

  if (!GST_FLAG_IS_SET (element, GST_ELEMENT_USE_THREADSAFE_PROPERTIES)) {
    g_object_get_valist (object, first_property_name, var_args);
    return;
  }

  g_object_ref (object);
  
  name = first_property_name;
  
  while (name)
    {
      GValue value = { 0, };
      GParamSpec *pspec;
      gchar *error;
      
      pspec =  g_object_class_find_property (G_OBJECT_GET_CLASS (object), name);

      if (!pspec)
	{
	  g_warning ("%s: object class `%s' has no property named `%s'",
		     G_STRLOC,
		     G_OBJECT_TYPE_NAME (object),
		     name);
	  break;
	}
      if (!(pspec->flags & G_PARAM_READABLE))
	{
	  g_warning ("%s: property `%s' of object class `%s' is not readable",
		     G_STRLOC,
		     pspec->name,
		     G_OBJECT_TYPE_NAME (object));
	  break;
	}
      
      g_value_init (&value, G_PARAM_SPEC_VALUE_TYPE (pspec));
      
      element_get_property (element, pspec, &value);
      
      G_VALUE_LCOPY (&value, var_args, 0, &error);
      if (error)
	{
	  g_warning ("%s: %s", G_STRLOC, error);
	  g_free (error);
	  g_value_unset (&value);
	  break;
	}
      
      g_value_unset (&value);
      
      name = va_arg (var_args, gchar*);
    }
  
  g_object_unref (object);
}

/**
 * gst_element_set_property:
 * @element: a #GstElement to set properties on.
 * @property_name: the first property to get.
 * @value: the #GValue that holds the value to set.
 *
 * Sets a property on an element. If the element uses threadsafe properties,
 * the property will be put on the async queue.
 */
void
gst_element_set_property (GstElement *element, const gchar *property_name, 
		          const GValue *value)
{
  GParamSpec *pspec;
  GObject *object;
  
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (property_name != NULL);
  g_return_if_fail (G_IS_VALUE (value));
  
  object = (GObject*) element;

  GST_DEBUG (GST_CAT_PROPERTIES, "setting property %s on element %s",
	     property_name, gst_element_get_name (element));
  if (!GST_FLAG_IS_SET (element, GST_ELEMENT_USE_THREADSAFE_PROPERTIES)) {
    g_object_set_property (object, property_name, value);
    return;
  }

  g_object_ref (object);
  
  pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (object), 
		                        property_name);
  
  if (!pspec)
    g_warning ("%s: object class `%s' has no property named `%s'",
	       G_STRLOC,
	       G_OBJECT_TYPE_NAME (object),
	       property_name);
  else
    element_set_property (element, pspec, value);
  
  g_object_unref (object);
}
  
/**
 * gst_element_get_property:
 * @element: a #GstElement to get properties of.
 * @property_name: the first property to get.
 * @value: the #GValue to store the property value in.
 *
 * Gets a property from an element. If the element uses threadsafe properties,
 * the element will be locked before getting the given property.
 */
void
gst_element_get_property (GstElement *element, const gchar *property_name, GValue *value)
{
  GParamSpec *pspec;
  GObject *object;
  
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (property_name != NULL);
  g_return_if_fail (G_IS_VALUE (value));
  
  object = (GObject*)element;

  if (!GST_FLAG_IS_SET (element, GST_ELEMENT_USE_THREADSAFE_PROPERTIES)) {
    g_object_get_property (object, property_name, value);
    return;
  }

  g_object_ref (object);
  
  pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (object), property_name);
  
  if (!pspec)
    g_warning ("%s: object class `%s' has no property named `%s'",
	       G_STRLOC,
	       G_OBJECT_TYPE_NAME (object),
	       property_name);
  else
    {
      GValue *prop_value, tmp_value = { 0, };
      
      /* auto-conversion of the callers value type
       */
      if (G_VALUE_TYPE (value) == G_PARAM_SPEC_VALUE_TYPE (pspec))
	{
	  g_value_reset (value);
	  prop_value = value;
	}
      else if (!g_value_type_transformable (G_PARAM_SPEC_VALUE_TYPE (pspec), G_VALUE_TYPE (value)))
	{
	  g_warning ("can't retrieve property `%s' of type `%s' as value of type `%s'",
		     pspec->name,
		     g_type_name (G_PARAM_SPEC_VALUE_TYPE (pspec)),
		     G_VALUE_TYPE_NAME (value));
	  g_object_unref (object);
	  return;
	}
      else
	{
	  g_value_init (&tmp_value, G_PARAM_SPEC_VALUE_TYPE (pspec));
	  prop_value = &tmp_value;
	}
      element_get_property (element, pspec, prop_value);
      if (prop_value != value)
	{
	  g_value_transform (prop_value, value);
	  g_value_unset (&tmp_value);
	}
    }
  
  g_object_unref (object);
}

static GstPad*
gst_element_request_pad (GstElement *element, GstPadTemplate *templ, const gchar* name)
{
  GstPad *newpad = NULL;
  GstElementClass *oclass;

  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->request_new_pad)
    newpad = (oclass->request_new_pad)(element, templ, name);

  return newpad;
}

/**
 * gst_element_release_request_pad:
 * @element: a #GstElement to release the request pad of.
 * @pad: the #GstPad to release.
 *
 * Makes the element free the previously requested pad as obtained
 * with gst_element_get_request_pad().
 */
void
gst_element_release_request_pad (GstElement *element, GstPad *pad)
{
  GstElementClass *oclass;

  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (GST_IS_PAD (pad));

  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->release_pad)
    (oclass->release_pad) (element, pad);
}

/**
 * gst_element_requires_clock:
 * @element: a #GstElement to query
 *
 * Query if the element requiresd a clock
 *
 * Returns: TRUE if the element requires a clock
 */
gboolean
gst_element_requires_clock (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  return (GST_ELEMENT_GET_CLASS (element)->set_clock != NULL);
}

/**
 * gst_element_provides_clock:
 * @element: a #GstElement to query
 *
 * Query if the element provides a clock
 *
 * Returns: TRUE if the element provides a clock
 */
gboolean
gst_element_provides_clock (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  return (GST_ELEMENT_GET_CLASS (element)->get_clock != NULL);
}

/**
 * gst_element_set_clock:
 * @element: a #GstElement to set the clock for.
 * @clock: the #GstClock to set for the element.
 *
 * Sets the clock for the element.
 */
void
gst_element_set_clock (GstElement *element, GstClock *clock)
{
  GstElementClass *oclass;

  g_return_if_fail (GST_IS_ELEMENT (element));

  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->set_clock)
    oclass->set_clock (element, clock);

  gst_object_replace ((GstObject **)&element->clock, (GstObject *)clock);
}

/**
 * gst_element_get_clock:
 * @element: a #GstElement to get the clock of.
 *
 * Gets the clock of the element.
 *
 * Returns: the #GstClock of the element.
 */
GstClock*
gst_element_get_clock (GstElement *element)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  oclass = GST_ELEMENT_GET_CLASS (element);
  
  if (oclass->get_clock)
    return oclass->get_clock (element);

  return NULL;
}

/**
 * gst_element_clock_wait:
 * @element: a #GstElement.
 * @id: the #GstClock to use.
 * @jitter: the difference between requested time and actual time.
 *
 * Waits for a specific time on the clock.
 *
 * Returns: the #GstClockReturn result of the wait operation.
 */
GstClockReturn
gst_element_clock_wait (GstElement *element, GstClockID id, GstClockTimeDiff *jitter)
{
  GstClockReturn res;

  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_CLOCK_ERROR);

  if (GST_ELEMENT_SCHED (element)) {
    res = gst_scheduler_clock_wait (GST_ELEMENT_SCHED (element), element, id, jitter);
  }
  else 
    res = GST_CLOCK_TIMEOUT;

  return res;
}

#ifndef GST_DISABLE_INDEX
/**
 * gst_element_is_indexable:
 * @element: a #GstElement.
 *
 * Queries if the element can be indexed/
 *
 * Returns: TRUE if the element can be indexed.
 */
gboolean
gst_element_is_indexable (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  return (GST_ELEMENT_GET_CLASS (element)->set_index != NULL);
}

/**
 * gst_element_set_index:
 * @element: a #GstElement.
 * @index: a #GstIndex.
 *
 * Set the specified GstIndex on the element.
 */
void
gst_element_set_index (GstElement *element, GstIndex *index)
{
  GstElementClass *oclass;

  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (GST_IS_INDEX (index));

  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->set_index)
    oclass->set_index (element, index);
}

/**
 * gst_element_get_index:
 * @element: a #GstElement.
 *
 * Gets the index from the element.
 *
 * Returns: a #GstIndex or NULL when no index was set on the
 * element.
 */
GstIndex*
gst_element_get_index (GstElement *element)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->get_index)
    return oclass->get_index (element);

  return NULL;
}
#endif

/**
 * gst_element_release_locks:
 * @element: a #GstElement to release all locks on.
 *
 * Instruct the element to release all the locks it is holding, such as
 * blocking reads, waiting for the clock, ...
 *
 * Returns: TRUE if the locks could be released.
 */
gboolean
gst_element_release_locks (GstElement *element)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->release_locks)
    return oclass->release_locks (element);
  
  return TRUE;
}

/**
 * gst_element_add_pad:
 * @element: a #GstElement to add the pad to.
 * @pad: the #GstPad to add to the element.
 *
 * Add a pad (link point) to the element, setting the parent of the
 * pad to the element (and thus adding a reference).
 */
void
gst_element_add_pad (GstElement *element, GstPad *pad)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_PAD (pad));

  /* first check to make sure the pad's parent is already set */
  g_return_if_fail (GST_PAD_PARENT (pad) == NULL);

  /* then check to see if there's already a pad by that name here */
  g_return_if_fail (gst_object_check_uniqueness (element->pads, GST_PAD_NAME(pad)) == TRUE);

  /* set the pad's parent */
  GST_DEBUG (GST_CAT_ELEMENT_PADS,"setting parent of pad '%s' to '%s'",
        GST_PAD_NAME (pad), GST_ELEMENT_NAME (element));
  gst_object_set_parent (GST_OBJECT (pad), GST_OBJECT (element));

  /* add it to the list */
  element->pads = g_list_append (element->pads, pad);
  element->numpads++;
  if (gst_pad_get_direction (pad) == GST_PAD_SRC)
    element->numsrcpads++;
  else
    element->numsinkpads++;

  /* emit the NEW_PAD signal */
  g_signal_emit (G_OBJECT (element), gst_element_signals[NEW_PAD], 0, pad);
}

/**
 * gst_element_remove_pad:
 * @element: a #GstElement to remove pad from.
 * @pad: the #GstPad to remove from the element.
 *
 * Remove a pad (link point) from the element.
 */
void
gst_element_remove_pad (GstElement *element, GstPad *pad)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_PAD (pad));

  g_return_if_fail (GST_PAD_PARENT (pad) == element);

  /* check to see if the pad is still linked */
  /* FIXME: what if someone calls _remove_pad instead of 
    _remove_ghost_pad? */
  if (GST_IS_REAL_PAD (pad)) {
    g_return_if_fail (GST_RPAD_PEER (pad) == NULL);
  }
  
  /* remove it from the list */
  element->pads = g_list_remove (element->pads, pad);
  element->numpads--;
  if (gst_pad_get_direction (pad) == GST_PAD_SRC)
    element->numsrcpads--;
  else
    element->numsinkpads--;

  g_signal_emit (G_OBJECT (element), gst_element_signals[PAD_REMOVED], 0, pad);

  gst_object_unparent (GST_OBJECT (pad));
}

/**
 * gst_element_add_ghost_pad:
 * @element: a #GstElement to add the ghost pad to.
 * @pad: the #GstPad from which the new ghost pad will be created.
 * @name: the name of the new ghost pad.
 *
 * Creates a ghost pad from the given pad, and adds it to the list of pads
 * for this element.
 * 
 * Returns: the added ghost #GstPad, or NULL, if no ghost pad was created.
 */
GstPad *
gst_element_add_ghost_pad (GstElement *element, GstPad *pad, const gchar *name)
{
  GstPad *ghostpad;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  /* then check to see if there's already a pad by that name here */
  g_return_val_if_fail (gst_object_check_uniqueness (element->pads, name) == TRUE, NULL);

  GST_DEBUG (GST_CAT_ELEMENT_PADS, 
             "creating new ghost pad called %s, from pad %s:%s",
             name, GST_DEBUG_PAD_NAME(pad));
  ghostpad = gst_ghost_pad_new (name, pad);

  /* add it to the list */
  GST_DEBUG(GST_CAT_ELEMENT_PADS,"adding ghost pad %s to element %s",
            name, GST_ELEMENT_NAME (element));
  element->pads = g_list_append (element->pads, ghostpad);
  element->numpads++;
  /* set the parent of the ghostpad */
  gst_object_set_parent (GST_OBJECT (ghostpad), GST_OBJECT (element));

  GST_DEBUG(GST_CAT_ELEMENT_PADS,"added ghostpad %s:%s",GST_DEBUG_PAD_NAME(ghostpad));

  /* emit the NEW_GHOST_PAD signal */
  g_signal_emit (G_OBJECT (element), gst_element_signals[NEW_PAD], 0, ghostpad);
	
  return ghostpad;
}

/**
 * gst_element_remove_ghost_pad:
 * @element: a #GstElement to remove the ghost pad from.
 * @pad: ghost #GstPad to remove.
 *
 * Removes a ghost pad from an element.
 */
void
gst_element_remove_ghost_pad (GstElement *element, GstPad *pad)
{
  g_return_if_fail (element != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_GHOST_PAD (pad));

  /* FIXME this is redundant?
   * wingo 10-july-2001: I don't think so, you have to actually remove the pad
   * from the element. gst_pad_remove_ghost_pad just removes the ghostpad from
   * the real pad's ghost pad list
   */
  gst_pad_remove_ghost_pad (GST_PAD (GST_PAD_REALIZE (pad)), pad);
  gst_element_remove_pad (element, pad);
}


/**
 * gst_element_get_pad:
 * @element: a #GstElement to find pad of.
 * @name: the name of the pad to retrieve.
 *
 * Retrieves a pad from the element by name.
 *
 * Returns: requested #GstPad if found, otherwise NULL.
 */
GstPad*
gst_element_get_pad (GstElement *element, const gchar *name)
{
  GstPad *pad;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  pad = gst_element_get_static_pad (element, name);
  if (!pad) 
    pad = gst_element_get_request_pad (element, name);

  return pad;
}

/**
 * gst_element_get_static_pad:
 * @element: a #GstElement to find a static pad of.
 * @name: the name of the static #GstPad to retrieve.
 *
 * Retrieves a pad from the element by name. This version only retrieves
 * already-existing (i.e. 'static') pads.
 *
 * Returns: the requested #GstPad if found, otherwise NULL.
 */
GstPad *
gst_element_get_static_pad (GstElement *element, const gchar *name)
{
  GList *walk;
  
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  walk = element->pads;
  while (walk) {
    GstPad *pad;
    
    pad = GST_PAD(walk->data);
    if (strcmp (GST_PAD_NAME(pad), name) == 0) {
      GST_INFO (GST_CAT_ELEMENT_PADS, "found pad %s:%s", GST_DEBUG_PAD_NAME (pad));
      return pad;
    }
    walk = g_list_next (walk);
  }

  GST_INFO (GST_CAT_ELEMENT_PADS, "no such pad '%s' in element \"%s\"", name, GST_OBJECT_NAME (element));
  return NULL;
}

/**
 * gst_element_get_request_pad:
 * @element: a #GstElement to find a request pad of.
 * @name: the name of the request #GstPad to retrieve.
 *
 * Retrieves a pad from the element by name. This version only retrieves
 * request pads.
 *
 * Returns: requested #GstPad if found, otherwise NULL.
 */
GstPad*
gst_element_get_request_pad (GstElement *element, const gchar *name)
{
  GstPadTemplate *templ = NULL;
  GstPad *pad;
  const gchar *req_name = NULL;
  gboolean templ_found = FALSE;
  GList *list;
  gint n;
  const gchar *data;
  gchar *str, *endptr = NULL;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  if (strstr (name, "%")) {
    templ = gst_element_get_pad_template (element, name);
    req_name = NULL;
    if (templ)
      templ_found = TRUE;
  } else {
    list = gst_element_get_pad_template_list(element);
    while (!templ_found && list) {
      templ = (GstPadTemplate*) list->data;
      if (templ->presence == GST_PAD_REQUEST) {
        /* we know that %s and %d are the only possibilities because of sanity
           checks in gst_pad_template_new */
        GST_DEBUG (GST_CAT_PADS, "comparing %s to %s", name, templ->name_template);
        if ((str = strchr (templ->name_template, '%')) &&
            strncmp (templ->name_template, name, str - templ->name_template) == 0 &&
            strlen (name) > str - templ->name_template) {
          data = name + (str - templ->name_template);
          if (*(str+1) == 'd') {
            /* it's an int */
            n = (gint) strtol (data, &endptr, 10);
            if (endptr && *endptr == '\0') {
              templ_found = TRUE;
              req_name = name;
              break;
            }
          } else {
            /* it's a string */
            templ_found = TRUE;
            req_name = name;
            break;
          }
        }
      }
      list = list->next;
    }
  }
  
  if (!templ_found)
      return NULL;
  
  pad = gst_element_request_pad (element, templ, req_name);
  
  return pad;
}

/**
 * gst_element_get_pad_list:
 * @element: a #GstElement to get pads of.
 *
 * Retrieves a list of the pads associated with the element.
 *
 * Returns: the #GList of pads.
 */
const GList*
gst_element_get_pad_list (GstElement *element)
{
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  /* return the list of pads */
  return element->pads;
}

/**
 * gst_element_class_add_pad_template:
 * @klass: the #GstElementClass to add the pad template to.
 * @templ: a #GstPadTemplate to add to the element class.
 *
 * Adds a padtemplate to an element class. 
 * This is useful if you have derived a custom bin and wish to provide 
 * an on-request pad at runtime. Plug-in writers should use
 * gst_element_factory_add_pad_template instead.
 */
void
gst_element_class_add_pad_template (GstElementClass *klass, 
                                    GstPadTemplate *templ)
{
  g_return_if_fail (klass != NULL);
  g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
  g_return_if_fail (templ != NULL);
  g_return_if_fail (GST_IS_PAD_TEMPLATE (templ));
  
  klass->padtemplates = g_list_append (klass->padtemplates, templ);
  klass->numpadtemplates++;
}

/**
 * gst_element_get_pad_template_list:
 * @element: a #GstElement to get pad templates of.
 *
 * Retrieves a list of the pad templates associated with the element.
 *
 * Returns: the #GList of padtemplates.
 */
GList*
gst_element_get_pad_template_list (GstElement *element)
{
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  return GST_ELEMENT_GET_CLASS (element)->padtemplates;
}

/**
 * gst_element_get_pad_template:
 * @element: a #GstElement to get the pad template of.
 * @name: the name of the #GstPadTemplate to get.
 *
 * Retrieves a padtemplate from this element with the
 * given name.
 *
 * Returns: the #GstPadTemplate with the given name, or NULL if none was found. 
 * No unreferencing is necessary.
 */
GstPadTemplate*
gst_element_get_pad_template (GstElement *element, const gchar *name)
{
  GList *padlist;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (name != NULL, NULL);

  padlist = gst_element_get_pad_template_list (element);

  while (padlist) {
    GstPadTemplate *padtempl = (GstPadTemplate*) padlist->data;

    if (!strcmp (padtempl->name_template, name))
      return padtempl;

    padlist = g_list_next (padlist);
  }

  return NULL;
}

/**
 * gst_element_get_compatible_pad_template:
 * @element: a #GstElement to get a compatible pad template for.
 * @compattempl: the #GstPadTemplate to find a compatible template for.
 *
 * Generates a pad template for this element compatible with the given
 * template (meaning it is able to link with it).
 *
 * Returns: the #GstPadTemplate of the element that is compatible with
 * the given GstPadTemplate, or NULL if none was found. No unreferencing
 * is necessary.
 */
GstPadTemplate*
gst_element_get_compatible_pad_template (GstElement *element,
                                         GstPadTemplate *compattempl)
{
  GstPadTemplate *newtempl = NULL;
  GList *padlist;

  GST_DEBUG (GST_CAT_ELEMENT_PADS, "gst_element_get_compatible_pad_template()");

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (compattempl != NULL, NULL);

  padlist = gst_element_get_pad_template_list (element);

  while (padlist) {
    GstPadTemplate *padtempl = (GstPadTemplate*) padlist->data;
    gboolean comp = FALSE;

    /* Ignore name
     * Ignore presence
     * Check direction (must be opposite)
     * Check caps
     */
    GST_DEBUG (GST_CAT_CAPS, "checking direction and caps");
    if (padtempl->direction == GST_PAD_SRC &&
      compattempl->direction == GST_PAD_SINK) {
      GST_DEBUG (GST_CAT_CAPS, "compatible direction: found src pad template");
      comp = gst_caps_is_always_compatible (GST_PAD_TEMPLATE_CAPS (padtempl),
				           GST_PAD_TEMPLATE_CAPS (compattempl));
      GST_DEBUG(GST_CAT_CAPS, "caps are %scompatible", (comp ? "" : "not "));
    } else if (padtempl->direction == GST_PAD_SINK &&
	       compattempl->direction == GST_PAD_SRC) {
      GST_DEBUG (GST_CAT_CAPS, "compatible direction: found sink pad template");
      comp = gst_caps_is_always_compatible (GST_PAD_TEMPLATE_CAPS (compattempl),
					   GST_PAD_TEMPLATE_CAPS (padtempl));
      GST_DEBUG (GST_CAT_CAPS, "caps are %scompatible", (comp ? "" : "not "));
    }

    if (comp) {
      newtempl = padtempl;
      break;
    }

    padlist = g_list_next (padlist);
  }

  return newtempl;
}

/**
 * gst_element_request_compatible_pad:
 * @element: a #GstElement to request a new pad from.
 * @templ: the #GstPadTemplate to which the new pad should be able to link.
 *
 * Requests a new pad from the element. The template will
 * be used to decide what type of pad to create. This function
 * is typically used for elements with a padtemplate with presence
 * GST_PAD_REQUEST.
 *
 * Returns: the new #GstPad that was created, or NULL if none could be created.
 */
GstPad*
gst_element_request_compatible_pad (GstElement *element, GstPadTemplate *templ)
{
  GstPadTemplate *templ_new;
  GstPad *pad = NULL;

  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (templ != NULL, NULL);

  templ_new = gst_element_get_compatible_pad_template (element, templ);
  if (templ_new != NULL)
      pad = gst_element_request_pad (element, templ_new, NULL);

  return pad;
}


/**
 * gst_element_get_compatible_pad_filtered:
 * @element: a #GstElement in which the pad should be found.
 * @pad: the #GstPad to find a compatible one for.
 * @filtercaps: the #GstCaps to use as a filter.
 *
 * Looks for an unlinked pad to which the given pad can link to.
 * It is not guaranteed that linking the pads will work, though
 * it should work in most cases.
 *
 * Returns: the #GstPad to which a link can be made.
 */
GstPad*
gst_element_get_compatible_pad_filtered (GstElement *element, GstPad *pad,
                                         GstCaps *filtercaps)
{
  const GList *pads;
  GstPadTemplate *templ;
  GstCaps *templcaps;
  GstPad *foundpad = NULL;

  /* checks */
  g_return_val_if_fail (element != NULL, NULL);
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  /* let's use the real pad */
  pad = (GstPad *) GST_PAD_REALIZE (pad);
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_RPAD_PEER (pad) == NULL, NULL);

  /* try to get an existing unlinked pad */
  pads = gst_element_get_pad_list (element);
  while (pads) {
    GstPad *current = GST_PAD (pads->data);
    if ((GST_PAD_PEER (GST_PAD_REALIZE (current)) == NULL) &&
        gst_pad_can_link_filtered (pad, current, filtercaps)) {
      return current;
    }
    pads = g_list_next (pads);
  }

  /* try to create a new one */
  /* requesting is a little crazy, we need a template. Let's create one */
  if (filtercaps != NULL) {
    templcaps = gst_caps_intersect (filtercaps, (GstCaps *) GST_RPAD_CAPS (pad));
    if (templcaps == NULL)
      return NULL;
  } else {
    templcaps = gst_pad_get_caps (pad);
  }

  templ = gst_pad_template_new ((gchar *) GST_PAD_NAME (pad), GST_RPAD_DIRECTION (pad),
                               GST_PAD_ALWAYS, templcaps, NULL);
  foundpad = gst_element_request_compatible_pad (element, templ);
  gst_object_unref (GST_OBJECT (templ)); /* this will take care of the caps too */

  /* FIXME: this is broken, but it's in here so autoplugging elements that don't
     have caps on their source padtemplates (spider) can link... */
  if (!foundpad && !filtercaps) {
    templ = gst_pad_template_new ((gchar *) GST_PAD_NAME (pad), GST_RPAD_DIRECTION (pad),
                                 GST_PAD_ALWAYS, NULL, NULL);
    foundpad = gst_element_request_compatible_pad (element, templ);
    gst_object_unref (GST_OBJECT (templ));
  }
  
  return foundpad;
}

/**
 * gst_element_get_compatible_pad:
 * @element: a #GstElement in which the pad should be found.
 * @pad: the #GstPad to find a compatible one for.
 *
 * Looks for an unlinked pad to which the given pad can link to.
 * It is not guaranteed that linking the pads will work, though
 * it should work in most cases.
 *
 * Returns: the #GstPad to which a link can be made, or NULL if none
 * could be found.
 */
GstPad*			
gst_element_get_compatible_pad (GstElement *element, GstPad *pad)
{
  return gst_element_get_compatible_pad_filtered (element, pad, NULL);
}

/**
 * gst_element_link_pads_filtered:
 * @src: a #GstElement containing the source pad.
 * @srcpadname: the name of the #GstPad in source element or NULL for any element.
 * @dest: the #GstElement containing the destination pad.
 * @destpadname: the name of the #GstPad in destination element or NULL for any element.
 * @filtercaps: the #GstCaps to use as a filter.
 *
 * Links the two named pads of the source and destination elements.
 * Side effect is that if one of the pads has no parent, it becomes a
 * child of the parent of the other element.  If they have different
 * parents, the link fails.
 *
 * Returns: TRUE if the pads could be linked.
 */
gboolean
gst_element_link_pads_filtered (GstElement *src, const gchar *srcpadname,
                                GstElement *dest, const gchar *destpadname,
                                GstCaps *filtercaps)
{
  const GList *srcpads, *destpads, *srctempls, *desttempls, *l;
  GstPad *srcpad, *destpad;
  GstPadTemplate *srctempl, *desttempl;

  /* checks */
  g_return_val_if_fail (GST_IS_ELEMENT (src), FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (dest), FALSE);
  g_return_val_if_fail (GST_STATE (src) != GST_STATE_PLAYING, FALSE);
  g_return_val_if_fail (GST_STATE (dest) != GST_STATE_PLAYING, FALSE);

  GST_INFO (GST_CAT_ELEMENT_PADS, "trying to link element %s:%s to element %s:%s",
            GST_ELEMENT_NAME (src), srcpadname ? srcpadname : "(any)", 
            GST_ELEMENT_NAME (dest), destpadname ? destpadname : "(any)");

  /* now get the pads we're trying to link and a list of all remaining pads */
  if (srcpadname) {
    srcpad = gst_element_get_pad (src, srcpadname);
    if (!srcpad) {
      GST_DEBUG (GST_CAT_ELEMENT_PADS, "no pad %s:%s", GST_ELEMENT_NAME (src), srcpadname);    
      return FALSE;
    } else {
      if (!(GST_RPAD_DIRECTION (srcpad) == GST_PAD_SRC)) {
        GST_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is no src pad", GST_DEBUG_PAD_NAME (srcpad));    
        return FALSE;
      }
      if (GST_PAD_PEER (srcpad) != NULL) {
        GST_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is already linked", GST_DEBUG_PAD_NAME (srcpad));    
        return FALSE;
      }
    }    
    srcpads = NULL;
  } else {
    srcpads = gst_element_get_pad_list (src);
    srcpad = srcpads ? (GstPad *) GST_PAD_REALIZE (srcpads->data) : NULL;
  }
  if (destpadname) {
    destpad = gst_element_get_pad (dest, destpadname);
    if (!destpad) {
      GST_DEBUG (GST_CAT_ELEMENT_PADS, "no pad %s:%s", GST_ELEMENT_NAME (dest), destpadname);    
      return FALSE;
    } else {
      if (!(GST_RPAD_DIRECTION (destpad) == GST_PAD_SINK)) {
        GST_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is no sink pad", GST_DEBUG_PAD_NAME (destpad));    
        return FALSE;
      }
      if (GST_PAD_PEER (destpad) != NULL) {
        GST_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is already linked", GST_DEBUG_PAD_NAME (destpad));    
        return FALSE;
      }
    }
    destpads = NULL;
  } else {
    destpads = gst_element_get_pad_list (dest);
    destpad = destpads ? (GstPad *) GST_PAD_REALIZE (destpads->data) : NULL;
  }

  if (srcpadname && destpadname) {
    /* two explicitly specified pads */
    return gst_pad_link_filtered (srcpad, destpad, filtercaps);  
  }
  if (srcpad) {
    /* loop through the allowed pads in the source, trying to find a
     * compatible destination pad */
    GST_DEBUG (GST_CAT_ELEMENT_PADS, "looping through allowed src and dest pads");
    do {
      GST_DEBUG (GST_CAT_ELEMENT_PADS, "trying src pad %s:%s", 
		 GST_DEBUG_PAD_NAME (srcpad));
      if ((GST_RPAD_DIRECTION (srcpad) == GST_PAD_SRC) &&
          (GST_PAD_PEER (srcpad) == NULL)) {
        GstPad *temp = gst_element_get_compatible_pad_filtered (dest, srcpad, 
	                                                   filtercaps);
        if (temp && gst_pad_link_filtered (srcpad, temp, filtercaps)) {
          GST_DEBUG (GST_CAT_ELEMENT_PADS, "linked pad %s:%s to pad %s:%s", 
	             GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (temp));
          return TRUE;
        }
      }
      /* find a better way for this mess */
      if (srcpads) {
	srcpads = g_list_next (srcpads);
        if (srcpads)
	  srcpad = (GstPad *) GST_PAD_REALIZE (srcpads->data);
      }
    } while (srcpads);
  }
  if (srcpadname) {
    GST_DEBUG (GST_CAT_ELEMENT_PADS, "no link possible from %s:%s to %s", 
               GST_DEBUG_PAD_NAME (srcpad), GST_ELEMENT_NAME (dest));
    return FALSE;
  }
  if (destpad) {    
    /* loop through the existing pads in the destination */
    do {
      GST_DEBUG (GST_CAT_ELEMENT_PADS, "trying dest pad %s:%s", 
		 GST_DEBUG_PAD_NAME (destpad));
      if ((GST_RPAD_DIRECTION (destpad) == GST_PAD_SINK) &&
          (GST_PAD_PEER (destpad) == NULL)) {
        GstPad *temp = gst_element_get_compatible_pad_filtered (src, destpad, 
	                                                  filtercaps);
        if (temp && gst_pad_link_filtered (temp, destpad, filtercaps)) {
          GST_DEBUG (GST_CAT_ELEMENT_PADS, "linked pad %s:%s to pad %s:%s", 
	             GST_DEBUG_PAD_NAME (temp), GST_DEBUG_PAD_NAME (destpad));
          return TRUE;
        }
      }
      if (destpads) {
	destpads = g_list_next (destpads);
        if (destpads)
	  destpad = (GstPad *) GST_PAD_REALIZE (destpads->data);
      }
    } while (destpads);
  }
  if (destpadname) {
    GST_DEBUG (GST_CAT_ELEMENT_PADS, "no link possible from %s to %s:%s", 
               GST_ELEMENT_NAME (src), GST_DEBUG_PAD_NAME (destpad));
    return FALSE;
  }

  GST_DEBUG (GST_CAT_ELEMENT_PADS, 
             "we might have request pads on both sides, checking...");
  srctempls = gst_element_get_pad_template_list (src);
  desttempls = gst_element_get_pad_template_list (dest);
  
  if (srctempls && desttempls) {
    while (srctempls) {
      srctempl = (GstPadTemplate*) srctempls->data;
      if (srctempl->presence == GST_PAD_REQUEST) {
        for (l=desttempls; l; l=l->next) {
          desttempl = (GstPadTemplate*) desttempls->data;
          if (desttempl->presence == GST_PAD_REQUEST && 
	      desttempl->direction != srctempl->direction) {
            if (gst_caps_is_always_compatible (gst_pad_template_get_caps (srctempl),
                                              gst_pad_template_get_caps (desttempl))) {
              srcpad = gst_element_get_request_pad (src, 
		                                    srctempl->name_template);
              destpad = gst_element_get_request_pad (dest, 
		                                     desttempl->name_template);
              if (gst_pad_link_filtered (srcpad, destpad, filtercaps)) {
                GST_DEBUG (GST_CAT_ELEMENT_PADS, 
		           "linked pad %s:%s to pad %s:%s",
                           GST_DEBUG_PAD_NAME (srcpad), 
			   GST_DEBUG_PAD_NAME (destpad));
                return TRUE;
              }
              /* FIXME: we have extraneous request pads lying around */
            }
          }
        }
      }
      srctempls = srctempls->next;
    }
  }
  
  GST_DEBUG (GST_CAT_ELEMENT_PADS, "no link possible from %s to %s", 
             GST_ELEMENT_NAME (src), GST_ELEMENT_NAME (dest));
  return FALSE;  
}
/**
 * gst_element_link_filtered:
 * @src: a #GstElement containing the source pad.
 * @dest: the #GstElement containing the destination pad.
 * @filtercaps: the #GstCaps to use as a filter.
 *
 * Links the source to the destination element using the filtercaps.
 * The link must be from source to destination, the other
 * direction will not be tried.
 * The functions looks for existing pads that aren't linked yet.
 * It will use request pads if possible. But both pads will not be requested.
 * If multiple links are possible, only one is established.
 *
 * Returns: TRUE if the elements could be linked.
 */
gboolean
gst_element_link_filtered (GstElement *src, GstElement *dest,
			      GstCaps *filtercaps)
{
  return gst_element_link_pads_filtered (src, NULL, dest, NULL, filtercaps);
}

/**
 * gst_element_link_many:
 * @element_1: the first #GstElement in the link chain.
 * @element_2: the second #GstElement in the link chain.
 * @...: the NULL-terminated list of elements to link in order.
 * 
 * Chain together a series of elements. Uses #gst_element_link.
 *
 * Returns: TRUE on success, FALSE otherwise.
 */
gboolean
gst_element_link_many (GstElement *element_1, GstElement *element_2, ...)
{
  va_list args;

  g_return_val_if_fail (element_1 != NULL && element_2 != NULL, FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (element_1) && 
                        GST_IS_ELEMENT (element_2), FALSE);

  va_start (args, element_2);

  while (element_2) {
    if (!gst_element_link (element_1, element_2))
      return FALSE;
    
    element_1 = element_2;
    element_2 = va_arg (args, GstElement*);
  }

  va_end (args);
  
  return TRUE;
}

/**
 * gst_element_link:
 * @src: a #GstElement containing the source pad.
 * @dest: the #GstElement containing the destination pad.
 *
 * Links the source to the destination element.
 * The link must be from source to destination, the other
 * direction will not be tried.
 * The functions looks for existing pads and request pads that aren't
 * linked yet. If multiple links are possible, only one is
 * established.
 *
 * Returns: TRUE if the elements could be linked.
 */
gboolean
gst_element_link (GstElement *src, GstElement *dest)
{
  return gst_element_link_pads_filtered (src, NULL, dest, NULL, NULL);
}

/**
 * gst_element_link_pads:
 * @src: a #GstElement containing the source pad.
 * @srcpadname: the name of the #GstPad in the source element.
 * @dest: the #GstElement containing the destination pad.
 * @destpadname: the name of the #GstPad in destination element.
 *
 * Links the two named pads of the source and destination elements.
 * Side effect is that if one of the pads has no parent, it becomes a
 * child of the parent of the other element.  If they have different
 * parents, the link fails.
 *
 * Returns: TRUE if the pads could be linked.
 */
gboolean
gst_element_link_pads (GstElement *src, const gchar *srcpadname,
                          GstElement *dest, const gchar *destpadname)
{
  return gst_element_link_pads_filtered (src, srcpadname, dest, destpadname, NULL);
}

/**
 * gst_element_unlink_pads:
 * @src: a #GstElement containing the source pad.
 * @srcpadname: the name of the #GstPad in source element.
 * @dest: a #GstElement containing the destination pad.
 * @destpadname: the name of the #GstPad in destination element.
 *
 * Unlinks the two named pads of the source and destination elements.
 */
void
gst_element_unlink_pads (GstElement *src, const gchar *srcpadname,
                             GstElement *dest, const gchar *destpadname)
{
  GstPad *srcpad,*destpad;

  g_return_if_fail (src != NULL);
  g_return_if_fail (GST_IS_ELEMENT(src));
  g_return_if_fail (srcpadname != NULL);
  g_return_if_fail (dest != NULL);
  g_return_if_fail (GST_IS_ELEMENT(dest));
  g_return_if_fail (destpadname != NULL);

  /* obtain the pads requested */
  srcpad = gst_element_get_pad (src, srcpadname);
  if (srcpad == NULL) {
    GST_ERROR(src,"source element has no pad \"%s\"",srcpadname);
    return;
  }
  destpad = gst_element_get_pad (dest, destpadname);
  if (srcpad == NULL) {
    GST_ERROR(dest,"destination element has no pad \"%s\"",destpadname);
    return;
  }

  /* we're satisified they can be unlinked, let's do it */
  gst_pad_unlink (srcpad,destpad);
}

/**
 * gst_element_unlink_many:
 * @element_1: the first #GstElement in the link chain.
 * @element_2: the second #GstElement in the link chain.
 * @...: the NULL-terminated list of elements to unlink in order.
 * 
 * Unlinks a series of elements. Uses #gst_element_unlink.
 */
void
gst_element_unlink_many (GstElement *element_1, GstElement *element_2, ...)
{
  va_list args;

  g_return_if_fail (element_1 != NULL && element_2 != NULL);
  g_return_if_fail (GST_IS_ELEMENT (element_1) && GST_IS_ELEMENT (element_2));

  va_start (args, element_2);

  while (element_2) {
    gst_element_unlink (element_1, element_2);
    
    element_1 = element_2;
    element_2 = va_arg (args, GstElement*);
  }

  va_end (args);
}

/**
 * gst_element_unlink:
 * @src: the source #GstElement to unlink.
 * @dest: the sink #GstElement to unlink.
 *
 * Unlinks all source pads of the source element with all sink pads
 * of the sink element to which they are linked.
 */
void
gst_element_unlink (GstElement *src, GstElement *dest)
{
  const GList *srcpads;
  GstPad *pad;

  g_return_if_fail (GST_IS_ELEMENT (src));
  g_return_if_fail (GST_IS_ELEMENT (dest));

  GST_DEBUG (GST_CAT_ELEMENT_PADS, "unlinking \"%s\" and \"%s\"",
             GST_ELEMENT_NAME (src), GST_ELEMENT_NAME (dest));

  srcpads = gst_element_get_pad_list (src);

  while (srcpads) {
    pad = GST_PAD_CAST (srcpads->data);

    /* we only care about real src pads */
    if (GST_IS_REAL_PAD (pad) && GST_PAD_IS_SRC (pad)) {
      GstPad *peerpad = GST_PAD_PEER (pad);

      /* see if the pad is connected and is really a pad
       * of dest */
      if (peerpad && 
	  (GST_OBJECT_PARENT (peerpad) == (GstObject*) dest)) 
      {
        gst_pad_unlink (pad, peerpad);
      }
    }

    srcpads = g_list_next (srcpads);
  }
}

static void
gst_element_error_func (GstElement* element, GstElement *source, 
                        gchar *errormsg)
{
  /* tell the parent */
  if (GST_OBJECT_PARENT (element)) {
    GST_DEBUG (GST_CAT_EVENT, "forwarding error \"%s\" from %s to %s", 
	       errormsg, GST_ELEMENT_NAME (element), 
	       GST_OBJECT_NAME (GST_OBJECT_PARENT (element)));

    gst_object_ref (GST_OBJECT (element));
    g_signal_emit (G_OBJECT (GST_OBJECT_PARENT (element)), 
	           gst_element_signals[ERROR], 0, source, errormsg);
    gst_object_unref (GST_OBJECT (element));
  }
}

static GstPad*
gst_element_get_random_pad (GstElement *element, GstPadDirection dir)
{
  GList *pads = element->pads;
  GST_DEBUG (GST_CAT_ELEMENT_PADS, "getting a random pad");
  while (pads) {
    GstPad *pad = GST_PAD_CAST (pads->data);

    GST_DEBUG (GST_CAT_ELEMENT_PADS, "checking pad %s:%s",
	       GST_DEBUG_PAD_NAME (pad));

    if (GST_PAD_DIRECTION (pad) == dir) {
      if (GST_PAD_IS_LINKED (pad)) {
	return pad;
      }
      else {
        GST_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is not linked",
	           GST_DEBUG_PAD_NAME (pad));
      }
    }
    else {
      GST_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is in wrong direction",
                 GST_DEBUG_PAD_NAME (pad));
    }

    pads = g_list_next (pads);
  }
  return NULL;
}

/**
 * gst_element_get_event_masks:
 * @element: a #GstElement to query
 *
 * Get an array of event masks from the element.
 * If the element doesn't 
 * implement an event masks function, the query will be forwarded
 * to a random linked sink pad.
 * 
 * Returns: An array of #GstEventMask elements.
 */
const GstEventMask*
gst_element_get_event_masks (GstElement *element)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  
  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->get_event_masks)
    return oclass->get_event_masks (element);
  else {
    GstPad *pad = gst_element_get_random_pad (element, GST_PAD_SINK);
    if (pad)
      return gst_pad_get_event_masks (GST_PAD_PEER (pad));
  }

  return FALSE;
}

/**
 * gst_element_send_event:
 * @element: a #GstElement to send the event to.
 * @event: the #GstEvent to send to the element.
 *
 * Sends an event to an element. If the element doesn't
 * implement an event handler, the event will be forwarded
 * to a random sink pad.
 *
 * Returns: TRUE if the event was handled.
 */
gboolean
gst_element_send_event (GstElement *element, GstEvent *event)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);
  
  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->send_event)
    return oclass->send_event (element, event);
  else {
    GstPad *pad = gst_element_get_random_pad (element, GST_PAD_SINK);
    if (pad) {
      GST_DEBUG (GST_CAT_ELEMENT_PADS, "sending event to random pad %s:%s",
		 GST_DEBUG_PAD_NAME (pad));
      return gst_pad_send_event (GST_PAD_PEER (pad), event);
    }
  }
  GST_DEBUG (GST_CAT_ELEMENT_PADS, "can't send event on element %s",
	     GST_ELEMENT_NAME (element));
  return FALSE;
}

/**
 * gst_element_get_query_types:
 * @element: a #GstElement to query
 *
 * Get an array of query types from the element.
 * If the element doesn't 
 * implement a query types function, the query will be forwarded
 * to a random sink pad.
 * 
 * Returns: An array of #GstQueryType elements.
 */
const GstQueryType*
gst_element_get_query_types (GstElement *element)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  
  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->get_query_types)
    return oclass->get_query_types (element);
  else {
    GstPad *pad = gst_element_get_random_pad (element, GST_PAD_SINK);
    if (pad)
      return gst_pad_get_query_types (GST_PAD_PEER (pad));
  }

  return FALSE;
}

/**
 * gst_element_query:
 * @element: a #GstElement to perform the query on.
 * @type: the #GstQueryType.
 * @format: the #GstFormat pointer to hold the format of the result.
 * @value: the pointer to the value of the result.
 *
 * Performs a query on the given element. If the format is set
 * to GST_FORMAT_DEFAULT and this function returns TRUE, the 
 * format pointer will hold the default format.
 * For element that don't implement a query handler, this function
 * forwards the query to a random usable sinkpad of this element.
 * 
 * Returns: TRUE if the query could be performed.
 */
gboolean
gst_element_query (GstElement *element, GstQueryType type,
		   GstFormat *format, gint64 *value)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  g_return_val_if_fail (format != NULL, FALSE);
  g_return_val_if_fail (value != NULL, FALSE);

  oclass = GST_ELEMENT_GET_CLASS (element);
  
  if (oclass->query)
    return oclass->query (element, type, format, value);
  else {
    GstPad *pad = gst_element_get_random_pad (element, GST_PAD_SINK);
    if (pad)
      return gst_pad_query (GST_PAD_PEER (pad), type, format, value);
  }

  return FALSE;
}

/**
 * gst_element_get_formats:
 * @element: a #GstElement to query
 *
 * Get an array of formst from the element.
 * If the element doesn't 
 * implement a formats function, the query will be forwarded
 * to a random sink pad.
 * 
 * Returns: An array of #GstFormat elements.
 */
const GstFormat*
gst_element_get_formats (GstElement *element)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  
  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->get_formats)
    return oclass->get_formats (element);
  else {
    GstPad *pad = gst_element_get_random_pad (element, GST_PAD_SINK);
    if (pad)
      return gst_pad_get_formats (GST_PAD_PEER (pad));
  }

  return FALSE;
}

/**
 * gst_element_convert:
 * @element: a #GstElement to invoke the converter on.
 * @src_format: the source #GstFormat.
 * @src_value: the source value.
 * @dest_format: a pointer to the destination #GstFormat.
 * @dest_value: a pointer to the destination value.
 *
 * Invokes a conversion on the element.
 * If the element doesn't 
 * implement a convert function, the query will be forwarded
 * to a random sink pad.
 *
 * Returns: TRUE if the conversion could be performed.
 */
gboolean
gst_element_convert (GstElement *element,
		     GstFormat  src_format,  gint64  src_value,
		     GstFormat *dest_format, gint64 *dest_value)
{
  GstElementClass *oclass;

  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
  g_return_val_if_fail (dest_format != NULL, FALSE);
  g_return_val_if_fail (dest_value != NULL, FALSE);

  if (src_format == *dest_format) {
    *dest_value = src_value;
    return TRUE;
  }

  oclass = GST_ELEMENT_GET_CLASS (element);

  if (oclass->convert)
    return oclass->convert (element,
		            src_format, src_value, 
		            dest_format, dest_value);
  else {
    GstPad *pad = gst_element_get_random_pad (element, GST_PAD_SINK);
    if (pad)
      return gst_pad_convert (GST_PAD_PEER (pad), 
		              src_format, src_value, 
		              dest_format, dest_value);
  }

  return FALSE;
}

/**
 * gst_element_error:
 * @element: a #GstElement with the error.
 * @error: the printf-style string describing the error.
 * @...: the optional arguments for the string.
 *
 * signals an error condition on an element.
 * This function is used internally by elements.
 * It results in the "error" signal.
 */
void
gst_element_error (GstElement *element, const gchar *error, ...)
{
  va_list var_args;
  gchar *string;
  
  /* checks */
  g_return_if_fail (GST_IS_ELEMENT (element));
  g_return_if_fail (error != NULL);

  /* create error message */
  va_start (var_args, error);
  string = g_strdup_vprintf (error, var_args);
  va_end (var_args);
  GST_INFO (GST_CAT_EVENT, "ERROR in %s: %s", GST_ELEMENT_NAME (element), string);

  /* emit the signal, make sure the element stays available */
  gst_object_ref (GST_OBJECT (element));
  g_signal_emit (G_OBJECT (element), gst_element_signals[ERROR], 0, element, string);
  
 /* tell the scheduler */
  if (element->sched) {
    gst_scheduler_error (element->sched, element); 
  } 

  if (GST_STATE (element) == GST_STATE_PLAYING)
    gst_element_set_state (element, GST_STATE_PAUSED);

  /* cleanup */
  gst_object_unref (GST_OBJECT (element));
  g_free (string);
}

/**
 * gst_element_is_state_locked:
 * @element: a #GstElement.
 *
 * Checks if the state of an element is locked.
 * If the state of an element is locked, state changes of the parent don't 
 * affect the element.
 * This way you can leave currently unused elements inside bins. Just lock their
 * state before changing the state from #GST_STATE_NULL.
 *
 * Returns: TRUE, if the element's state is locked.
 */
gboolean
gst_element_is_state_locked (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  return GST_FLAG_IS_SET (element, GST_ELEMENT_LOCKED_STATE) ? TRUE : FALSE;
}
/**
 * gst_element_lock_state:
 * @element: a #GstElement.
 *
 * Locks the state of an element, so state changes of the parent don't affect
 * this element anymore.
 *
 * Returns: TRUE, if the element's state could be locked.
 */
gboolean
gst_element_lock_state (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  GST_INFO (GST_CAT_STATES, "locking state of element %s\n", GST_ELEMENT_NAME (element));
  GST_FLAG_SET (element, GST_ELEMENT_LOCKED_STATE);
  return TRUE;
}
/**
 * gst_element_unlock_state:
 * @element: a #GstElement.
 *
 * Unlocks the state of an element and synchronises the state with the parent.
 * If this function succeeds, the state of this element is identical to the 
 * state of it's bin.
 * When this function fails, the state of the element is undefined.
 *
 * Returns: TRUE, if the element's state could be unlocked.
 */
gboolean 
gst_element_unlock_state (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

  GST_INFO (GST_CAT_STATES, "unlocking state of element %s\n", GST_ELEMENT_NAME (element));
  GST_FLAG_UNSET (element, GST_ELEMENT_LOCKED_STATE);  
  if (GST_ELEMENT_PARENT(element)) {
    GST_DEBUG (GST_CAT_STATES, "setting state of unlocked element %s to %s\n", GST_ELEMENT_NAME (element), gst_element_state_get_name (GST_STATE (GST_ELEMENT_PARENT(element))));
    GstElementState old_state = GST_STATE (element);
    if (gst_element_set_state (element, GST_STATE (GST_ELEMENT_PARENT(element))) == GST_STATE_FAILURE) {
      GST_DEBUG (GST_CAT_STATES, "state change of unlocked element %s to %s stopped at %s, resetting\n", GST_ELEMENT_NAME (element), 
                 gst_element_state_get_name (GST_STATE (GST_ELEMENT_PARENT(element))), gst_element_state_get_name (GST_STATE (element)));      
      gst_element_set_state (element, old_state);
      return FALSE;
    }
  }
  return TRUE;
}
/**
 * gst_element_get_state:
 * @element: a #GstElement to get the state of.
 *
 * Gets the state of the element. 
 *
 * Returns: the #GstElementState of the element.
 */
GstElementState
gst_element_get_state (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_VOID_PENDING);

  return GST_STATE (element);
}

/**
 * gst_element_wait_state_change:
 * @element: a #GstElement to wait for a state change on.
 *
 * Waits and blocks until the element changed its state.
 */
void
gst_element_wait_state_change (GstElement *element)
{
  g_mutex_lock (element->state_mutex);
  g_cond_wait (element->state_cond, element->state_mutex);
  g_mutex_unlock (element->state_mutex);
}

/**
 * gst_element_set_state:
 * @element: a #GstElement to change state of.
 * @state: the element's new #GstElementState.
 *
 * Sets the state of the element. This function will try to set the
 * requested state by going through all the intermediary states and calling
 * the class's state change function for each.
 *
 * Returns: TRUE if the state was successfully set.
 * (using #GstElementStateReturn).
 */
GstElementStateReturn
gst_element_set_state (GstElement *element, GstElementState state)
{
  GstElementClass *oclass;
  GstElementState curpending;
  GstElementStateReturn return_val = GST_STATE_SUCCESS;

  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_FAILURE);

  /* start with the current state */
  curpending = GST_STATE(element);

  GST_DEBUG_ELEMENT (GST_CAT_STATES, element, "setting state from %s to %s",
                     gst_element_state_get_name (curpending),
                     gst_element_state_get_name (state));

  /* loop until the final requested state is set */
  while (GST_STATE (element) != state 
      && GST_STATE (element) != GST_STATE_VOID_PENDING) {
    /* move the curpending state in the correct direction */
    if (curpending < state) 
      curpending <<= 1;
    else 
      curpending >>= 1;

    /* set the pending state variable */
    /* FIXME: should probably check to see that we don't already have one */
    GST_STATE_PENDING (element) = curpending;

    if (curpending != state) {
      GST_DEBUG_ELEMENT (GST_CAT_STATES, element, 
	                 "intermediate: setting state from %s to %s",
			 gst_element_state_get_name (GST_STATE (element)),
                         gst_element_state_get_name (curpending));
    }

    /* call the state change function so it can set the state */
    oclass = GST_ELEMENT_GET_CLASS (element);
    if (oclass->change_state)
      return_val = (oclass->change_state) (element);

    switch (return_val) {
      case GST_STATE_FAILURE:
        GST_DEBUG_ELEMENT (GST_CAT_STATES, element, 
	                   "have failed change_state return");
        goto exit;
      case GST_STATE_ASYNC:
        GST_DEBUG_ELEMENT (GST_CAT_STATES, element, 
	                   "element will change state async");
        goto exit;
      case GST_STATE_SUCCESS:
        /* Last thing we do is verify that a successful state change really
         * did change the state... */
        if (GST_STATE (element) != curpending) {
          GST_DEBUG_ELEMENT (GST_CAT_STATES, element, 
			     "element claimed state-change success,"
			     "but state didn't change %s, %s <-> %s",
                     	     gst_element_state_get_name (GST_STATE (element)),
                     	     gst_element_state_get_name (GST_STATE_PENDING (element)),
                     	     gst_element_state_get_name (curpending));
          return GST_STATE_FAILURE;
	}
        break;
      default:
	/* somebody added a GST_STATE_ and forgot to do stuff here ! */
	g_assert_not_reached ();
    }
  }
exit:

  return return_val;
}

static gboolean
gst_element_negotiate_pads (GstElement *element)
{
  GList *pads = GST_ELEMENT_PADS (element);

  GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, "negotiating pads");

  while (pads) {
    GstPad *pad = GST_PAD (pads->data);
    GstRealPad *srcpad;

    pads = g_list_next (pads);
    
    if (!GST_IS_REAL_PAD (pad))
      continue;

    srcpad = GST_PAD_REALIZE (pad);

    /* if we have a link on this pad and it doesn't have caps
     * allready, try to negotiate */
    if (GST_PAD_IS_LINKED (srcpad) && !GST_PAD_CAPS (srcpad)) {
      GstRealPad *sinkpad;
      GstElementState otherstate;
      GstElement *parent;
      
      sinkpad = GST_RPAD_PEER (GST_PAD_REALIZE (srcpad));

      /* check the parent of the peer pad, if there is no parent do nothing */
      parent = GST_PAD_PARENT (sinkpad);
      if (!parent) 
	continue;

      /* skips pads that were already negotiating */
      if (GST_FLAG_IS_SET (sinkpad, GST_PAD_NEGOTIATING) ||
          GST_FLAG_IS_SET (srcpad, GST_PAD_NEGOTIATING))
	continue;

      otherstate = GST_STATE (parent);

      /* swap pads if needed */
      if (!GST_PAD_IS_SRC (srcpad)) {
        GstRealPad *temp;

	temp = srcpad;
	srcpad = sinkpad;
	sinkpad = temp;
      }

      /* only try to negotiate if the peer element is in PAUSED or higher too */
      if (otherstate >= GST_STATE_READY) {
        GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, 
	                   "perform negotiate for %s:%s and %s:%s",
		           GST_DEBUG_PAD_NAME (srcpad), 
			   GST_DEBUG_PAD_NAME (sinkpad));
        if (!gst_pad_perform_negotiate (GST_PAD (srcpad), GST_PAD (sinkpad)))
	  return FALSE;
      }
      else {
        GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, 
	                   "not negotiating %s:%s and %s:%s, not in READY yet",
		           GST_DEBUG_PAD_NAME (srcpad), 
			   GST_DEBUG_PAD_NAME (sinkpad));
      }
    }
  }

  return TRUE;
}

static void
gst_element_clear_pad_caps (GstElement *element)
{
  GList *pads = GST_ELEMENT_PADS (element);

  GST_DEBUG_ELEMENT (GST_CAT_CAPS, element, "clearing pad caps");

  while (pads) {
    GstRealPad *pad = GST_PAD_REALIZE (pads->data);

    gst_caps_replace (&GST_PAD_CAPS (pad), NULL);

    pads = g_list_next (pads);
  }
}

static void
gst_element_pads_activate (GstElement *element, gboolean active)
{
  GList *pads = element->pads;

  while (pads) {
    GstPad *pad = GST_PAD_CAST (pads->data);
    pads = g_list_next (pads);

    if (!GST_IS_REAL_PAD (pad))
      continue;

    gst_pad_set_active (pad, active);
  }
}

static GstElementStateReturn
gst_element_change_state (GstElement *element)
{
  GstElementState old_state;
  GstObject *parent;
  gint old_pending, old_transition;

  g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_FAILURE);

  old_state = GST_STATE (element);
  old_pending = GST_STATE_PENDING (element);
  old_transition = GST_STATE_TRANSITION (element);

  if (old_pending == GST_STATE_VOID_PENDING || 
      old_state == GST_STATE_PENDING (element)) {
    GST_INFO (GST_CAT_STATES, 
	      "no state change needed for element %s (VOID_PENDING)", 
	      GST_ELEMENT_NAME (element));
    return GST_STATE_SUCCESS;
  }
  
  GST_INFO (GST_CAT_STATES, "%s default handler sets state from %s to %s %04x", 
            GST_ELEMENT_NAME (element),
            gst_element_state_get_name (old_state),
            gst_element_state_get_name (old_pending),
	    old_transition);

  /* we set the state change early for the negotiation functions */
  GST_STATE (element) = old_pending;
  GST_STATE_PENDING (element) = GST_STATE_VOID_PENDING;

  switch (old_transition) {
    case GST_STATE_PLAYING_TO_PAUSED:
      gst_element_pads_activate (element, FALSE);
      break;
    case GST_STATE_PAUSED_TO_PLAYING:
      gst_element_pads_activate (element, TRUE);
      break;
    /* if we are going to paused, we try to negotiate the pads */
    case GST_STATE_READY_TO_PAUSED:
      if (!gst_element_negotiate_pads (element)) 
        goto failure;
      break;
    /* going to the READY state clears all pad caps */
    case GST_STATE_PAUSED_TO_READY:
      gst_element_clear_pad_caps (element);
      break;
    default:
      break;
  }

  parent = GST_ELEMENT_PARENT (element);

  GST_DEBUG_ELEMENT (GST_CAT_STATES, element,
                     "signaling state change from %s to %s",
                     gst_element_state_get_name (old_state),
                     gst_element_state_get_name (GST_STATE (element)));

  /* tell the scheduler if we have one */
  if (element->sched) {
    if (gst_scheduler_state_transition (element->sched, element, 
	                                old_transition) != GST_STATE_SUCCESS) {
      GST_DEBUG_ELEMENT (GST_CAT_STATES, element, 
		         "scheduler could change state");
      goto failure;
    }
  }

  g_signal_emit (G_OBJECT (element), gst_element_signals[STATE_CHANGE],
		 0, old_state, GST_STATE (element));

  /* tell our parent about the state change */
  if (parent && GST_IS_BIN (parent)) {
    gst_bin_child_state_change (GST_BIN (parent), old_state, 
	                        GST_STATE (element), element);
  }

  /* signal the state change in case somebody is waiting for us */
  g_mutex_lock (element->state_mutex);
  g_cond_signal (element->state_cond);
  g_mutex_unlock (element->state_mutex);

  return GST_STATE_SUCCESS;

failure:
  /* undo the state change */
  GST_STATE (element) = old_state;
  GST_STATE_PENDING (element) = old_pending;

  return GST_STATE_FAILURE;
}

/**
 * gst_element_get_factory:
 * @element: a #GstElement to request the element factory of.
 *
 * Retrieves the factory that was used to create this element.
 *
 * Returns: the #GstElementFactory used for creating this element.
 */
GstElementFactory*
gst_element_get_factory (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  return GST_ELEMENT_GET_CLASS (element)->elementfactory;
}

static void
gst_element_dispose (GObject *object)
{
  GstElement *element = GST_ELEMENT (object);
  GList *pads;
  GstPad *pad;

  GST_DEBUG_ELEMENT (GST_CAT_REFCOUNTING, element, "dispose");

  gst_element_set_state (element, GST_STATE_NULL);

  /* first we break all our links with the ouside */
  if (element->pads) {
    GList *orig;
    orig = pads = g_list_copy (element->pads);
    while (pads) {
      pad = GST_PAD (pads->data);

      if (GST_PAD_PEER (pad)) {
        GST_DEBUG (GST_CAT_REFCOUNTING, "unlinking pad '%s'",
	           GST_OBJECT_NAME (GST_OBJECT (GST_PAD (GST_PAD_PEER (pad)))));
        gst_pad_unlink (pad, GST_PAD (GST_PAD_PEER (pad)));
      }
      gst_element_remove_pad (element, pad);

      pads = g_list_next (pads);
    }
    g_list_free (orig);
    g_list_free (element->pads);
    element->pads = NULL;
  }

  element->numsrcpads = 0;
  element->numsinkpads = 0;
  element->numpads = 0;
  g_mutex_free (element->state_mutex);
  g_cond_free (element->state_cond);

  if (element->prop_value_queue)
    g_async_queue_unref (element->prop_value_queue);
  element->prop_value_queue = NULL;
  if (element->property_mutex)
    g_mutex_free (element->property_mutex);

  gst_object_replace ((GstObject **)&element->sched, NULL);
  gst_object_replace ((GstObject **)&element->clock, NULL);

  G_OBJECT_CLASS (parent_class)->dispose (object);
}

#ifndef GST_DISABLE_LOADSAVE
/**
 * gst_element_save_thyself:
 * @element: a #GstElement to save.
 * @parent: the xml parent node.
 *
 * Saves the element as part of the given XML structure.
 *
 * Returns: the new #xmlNodePtr.
 */
static xmlNodePtr
gst_element_save_thyself (GstObject *object,
		          xmlNodePtr parent)
{
  GList *pads;
  GstElementClass *oclass;
  GParamSpec **specs, *spec;
  gint nspecs, i;
  GValue value = { 0, };
  GstElement *element;

  g_return_val_if_fail (GST_IS_ELEMENT (object), parent);

  element = GST_ELEMENT (object);

  oclass = GST_ELEMENT_GET_CLASS (element);

  xmlNewChild(parent, NULL, "name", GST_ELEMENT_NAME(element));

  if (oclass->elementfactory != NULL) {
    GstElementFactory *factory = (GstElementFactory *)oclass->elementfactory;

    xmlNewChild (parent, NULL, "type", GST_OBJECT_NAME (factory));
    xmlNewChild (parent, NULL, "version", factory->details->version);
  }

/* FIXME: what is this? */  
/*  if (element->manager) */
/*    xmlNewChild(parent, NULL, "manager", GST_ELEMENT_NAME(element->manager)); */

  /* params */
  specs = g_object_class_list_properties (G_OBJECT_GET_CLASS (object), &nspecs);
  
  for (i=0; i<nspecs; i++) {
    spec = specs[i];
    if (spec->flags & G_PARAM_READABLE) {
      xmlNodePtr param;
      char *contents;
      
      g_value_init(&value, G_PARAM_SPEC_VALUE_TYPE (spec));
      
      g_object_get_property (G_OBJECT (element), spec->name, &value);
      param = xmlNewChild (parent, NULL, "param", NULL);
      xmlNewChild (param, NULL, "name", spec->name);
      
      if (G_IS_PARAM_SPEC_STRING (spec))
	contents = g_value_dup_string (&value);
      else if (G_IS_PARAM_SPEC_ENUM (spec))
	contents = g_strdup_printf ("%d", g_value_get_enum (&value));
      else if (G_IS_PARAM_SPEC_INT64 (spec))
	contents = g_strdup_printf ("%" G_GINT64_FORMAT,
			            g_value_get_int64 (&value));
      else
	contents = g_strdup_value_contents (&value);
      
      xmlNewChild (param, NULL, "value", contents);
      g_free (contents);
      
      g_value_unset(&value);
    }
  }

  pads = GST_ELEMENT_PADS (element);

  while (pads) {
    GstPad *pad = GST_PAD (pads->data);
    /* figure out if it's a direct pad or a ghostpad */
    if (GST_ELEMENT (GST_OBJECT_PARENT (pad)) == element) {
      xmlNodePtr padtag = xmlNewChild (parent, NULL, "pad", NULL);
      gst_object_save_thyself (GST_OBJECT (pad), padtag);
    }
    pads = g_list_next (pads);
  }

  return parent;
}

static void
gst_element_restore_thyself (GstObject *object, xmlNodePtr self)
{
  xmlNodePtr children;
  GstElement *element;
  gchar *name = NULL;
  gchar *value = NULL;

  element = GST_ELEMENT (object);
  g_return_if_fail (element != NULL);

  /* parameters */
  children = self->xmlChildrenNode;
  while (children) {
    if (!strcmp (children->name, "param")) {
      xmlNodePtr child = children->xmlChildrenNode;

      while (child) {
        if (!strcmp (child->name, "name")) {
          name = xmlNodeGetContent (child);
	}
	else if (!strcmp (child->name, "value")) {
          value = xmlNodeGetContent (child);
	}
        child = child->next;
      }
      /* FIXME: can this just be g_object_set ? */
      gst_util_set_object_arg (G_OBJECT (element), name, value);
    }
    children = children->next;
  }
  
  /* pads */
  children = self->xmlChildrenNode;
  while (children) {
    if (!strcmp (children->name, "pad")) {
      gst_pad_load_and_link (children, GST_OBJECT (element));
    }
    children = children->next;
  }

  if (GST_OBJECT_CLASS (parent_class)->restore_thyself)
    (GST_OBJECT_CLASS (parent_class)->restore_thyself) (object, self);
}
#endif /* GST_DISABLE_LOADSAVE */

/**
 * gst_element_yield:
 * @element: a #GstElement to yield.
 *
 * Requests a yield operation for the element. The scheduler will typically
 * give control to another element.
 */
void
gst_element_yield (GstElement *element)
{
  if (GST_ELEMENT_SCHED (element)) {
    gst_scheduler_yield (GST_ELEMENT_SCHED (element), element);
  }
}

/**
 * gst_element_interrupt:
 * @element: a #GstElement to interrupt.
 *
 * Requests the scheduler of this element to interrupt the execution of
 * this element and scheduler another one.
 *
 * Returns: TRUE if the element should exit its chain/loop/get
 * function ASAP, depending on the scheduler implementation.
 */
gboolean
gst_element_interrupt (GstElement *element)
{
  if (GST_ELEMENT_SCHED (element)) {
    return gst_scheduler_interrupt (GST_ELEMENT_SCHED (element), element);
  }
  else 
    return TRUE;
}

/**
 * gst_element_set_scheduler:
 * @element: a #GstElement to set the scheduler of.
 * @sched: the #GstScheduler to set.
 *
 * Sets the scheduler of the element.  For internal use only, unless you're
 * writing a new bin subclass.
 */
void
gst_element_set_scheduler (GstElement *element,
		       GstScheduler *sched)
{
  g_return_if_fail (GST_IS_ELEMENT (element));
  
  GST_INFO_ELEMENT (GST_CAT_PARENTAGE, element, "setting scheduler to %p", sched);

  gst_object_replace ((GstObject **)&GST_ELEMENT_SCHED (element), GST_OBJECT (sched));
}

/**
 * gst_element_get_scheduler:
 * @element: a #GstElement to get the scheduler of.
 *
 * Returns the scheduler of the element.
 *
 * Returns: the element's #GstScheduler.
 */
GstScheduler*
gst_element_get_scheduler (GstElement *element)
{
  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);

  return GST_ELEMENT_SCHED (element);
}

/**
 * gst_element_set_loop_function:
 * @element: a #GstElement to set the loop function of.
 * @loop: Pointer to #GstElementLoopFunction.
 *
 * This sets the loop function for the element.  The function pointed to
 * can deviate from the GstElementLoopFunction definition in type of
 * pointer only.
 *
 * NOTE: in order for this to take effect, the current loop function *must*
 * exit.  Assuming the loop function itself is the only one who will cause
 * a new loopfunc to be assigned, this should be no problem.
 */
void
gst_element_set_loop_function (GstElement *element,
                               GstElementLoopFunction loop)
{
  gboolean need_notify = FALSE;
  
  g_return_if_fail (GST_IS_ELEMENT (element));

  /* if the element changed from loop based to chain/get based
   * or vice versa, we need to inform the scheduler about that */
  if ((element->loopfunc == NULL && loop != NULL) ||
      (element->loopfunc != NULL && loop == NULL))
  {
    need_notify = TRUE;
  }
  
  /* set the loop function */
  element->loopfunc = loop;

  if (need_notify) {
    /* set the NEW_LOOPFUNC flag so everyone knows to go try again */
    GST_FLAG_SET (element, GST_ELEMENT_NEW_LOOPFUNC);

    if (GST_ELEMENT_SCHED (element)) {
      gst_scheduler_scheduling_change (GST_ELEMENT_SCHED (element), element);
    }
  }
}

/**
 * gst_element_set_eos:
 * @element: a #GstElement to set to the EOS state.
 *
 * Perform the actions needed to bring the element in the EOS state.
 */
void
gst_element_set_eos (GstElement *element)
{
  g_return_if_fail (GST_IS_ELEMENT (element));

  GST_DEBUG (GST_CAT_EVENT, "setting EOS on element %s", 
             GST_OBJECT_NAME (element));

  gst_element_set_state (element, GST_STATE_PAUSED);

  g_signal_emit (G_OBJECT (element), gst_element_signals[EOS], 0);
}


/**
 * gst_element_state_get_name:
 * @state: a #GstElementState to get the name of.
 *
 * Gets a string representing the given state.
 *
 * Returns: a string with the name of the state.
 */
const gchar*
gst_element_state_get_name (GstElementState state) 
{
  switch (state) {
#ifdef GST_DEBUG_COLOR
    case GST_STATE_VOID_PENDING: return "NONE_PENDING";break;
    case GST_STATE_NULL: return "\033[01;37mNULL\033[00m";break;
    case GST_STATE_READY: return "\033[01;31mREADY\033[00m";break;
    case GST_STATE_PLAYING: return "\033[01;32mPLAYING\033[00m";break;
    case GST_STATE_PAUSED: return "\033[01;33mPAUSED\033[00m";break;
    default:
      /* This is a memory leak */
      return g_strdup_printf ("\033[01;37;41mUNKNOWN!\033[00m(%d)", state);
#else
    case GST_STATE_VOID_PENDING: return "NONE_PENDING";break;
    case GST_STATE_NULL: return "NULL";break;
    case GST_STATE_READY: return "READY";break;
    case GST_STATE_PLAYING: return "PLAYING";break;
    case GST_STATE_PAUSED: return "PAUSED";break;
    default: return "UNKNOWN!";
#endif
  }
  return "";
}

static void
gst_element_populate_std_props (GObjectClass * klass, const gchar *prop_name, 
                                guint arg_id, GParamFlags flags)
{
  GQuark prop_id = g_quark_from_string (prop_name);
  GParamSpec *pspec;

  static GQuark fd_id = 0;
  static GQuark blocksize_id;
  static GQuark bytesperread_id;
  static GQuark dump_id;
  static GQuark filesize_id;
  static GQuark mmapsize_id;
  static GQuark location_id;
  static GQuark offset_id;
  static GQuark silent_id;
  static GQuark touch_id;

  if (!fd_id) {
    fd_id = g_quark_from_static_string ("fd");
    blocksize_id = g_quark_from_static_string ("blocksize");
    bytesperread_id = g_quark_from_static_string ("bytesperread");
    dump_id = g_quark_from_static_string ("dump");
    filesize_id = g_quark_from_static_string ("filesize");
    mmapsize_id = g_quark_from_static_string ("mmapsize");
    location_id = g_quark_from_static_string ("location");
    offset_id = g_quark_from_static_string ("offset");
    silent_id = g_quark_from_static_string ("silent");
    touch_id = g_quark_from_static_string ("touch");
  }

  if (prop_id == fd_id) {
    pspec = g_param_spec_int ("fd", "File-descriptor",
			      "File-descriptor for the file being read",
			      0, G_MAXINT, 0, flags);
  }
  else if (prop_id == blocksize_id) {
    pspec = g_param_spec_ulong ("blocksize", "Block Size",
				"Block size to read per buffer",
				0, G_MAXULONG, 4096, flags);

  }
  else if (prop_id == bytesperread_id) {
    pspec = g_param_spec_int ("bytesperread", "Bytes per read",
			      "Number of bytes to read per buffer",
			      G_MININT, G_MAXINT, 0, flags);

  }
  else if (prop_id == dump_id) {
    pspec = g_param_spec_boolean ("dump", "Dump", 
	                          "Dump bytes to stdout", 
				  FALSE, flags);

  }
  else if (prop_id == filesize_id) {
    pspec = g_param_spec_int64 ("filesize", "File Size",
				"Size of the file being read",
				0, G_MAXINT64, 0, flags);

  }
  else if (prop_id == mmapsize_id) {
    pspec = g_param_spec_ulong ("mmapsize", "mmap() Block Size",
				"Size in bytes of mmap()d regions",
				0, G_MAXULONG, 4 * 1048576, flags);

  }
  else if (prop_id == location_id) {
    pspec = g_param_spec_string ("location", "File Location",
				 "Location of the file to read",
				 NULL, flags);

  }
  else if (prop_id == offset_id) {
    pspec = g_param_spec_int64 ("offset", "File Offset",
				"Byte offset of current read pointer",
				0, G_MAXINT64, 0, flags);

  }
  else if (prop_id == silent_id) {
    pspec = g_param_spec_boolean ("silent", "Silent", "Don't produce events",
				  FALSE, flags);

  }
  else if (prop_id == touch_id) {
    pspec = g_param_spec_boolean ("touch", "Touch read data",
				  "Touch data to force disk read before "
				  "push ()", TRUE, flags);
  }
  else {
    g_warning ("Unknown - 'standard' property '%s' id %d from klass %s",
               prop_name, arg_id, g_type_name (G_OBJECT_CLASS_TYPE (klass)));
    pspec = NULL;
  }

  if (pspec) {
    g_object_class_install_property (klass, arg_id, pspec);
  }
}

/**
 * gst_element_class_install_std_props:
 * @klass: the #GstElementClass to add the properties to.
 * @first_name: the name of the first property.
 * in a NULL terminated
 * @...: the id and flags of the first property, followed by
 * further 'name', 'id', 'flags' triplets and terminated by NULL.
 * 
 * Adds a list of standardized properties with types to the @klass.
 * the id is for the property switch in your get_prop method, and
 * the flags determine readability / writeability.
 **/
void
gst_element_class_install_std_props (GstElementClass * klass, 
                                     const gchar *first_name, ...)
{
  const char *name;

  va_list args;

  g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));

  va_start (args, first_name);

  name = first_name;

  while (name) {
    int arg_id = va_arg (args, int);
    int flags = va_arg (args, int);

    gst_element_populate_std_props ((GObjectClass *) klass, name, arg_id, flags);

    name = va_arg (args, char *);
  }

  va_end (args);
}

/**
 * gst_element_get_managing_bin:
 * @element: a #GstElement to get the managing bin of.
 * 
 * Gets the managing bin (a pipeline or a thread, for example) of an element.
 *
 * Returns: the #GstBin, or NULL on failure.
 **/
GstBin*
gst_element_get_managing_bin (GstElement *element)
{
  GstBin *bin;

  g_return_val_if_fail (element != NULL, NULL);

  bin = GST_BIN (gst_object_get_parent (GST_OBJECT_CAST (element)));

  while (bin && !GST_FLAG_IS_SET (GST_OBJECT_CAST (bin), GST_BIN_FLAG_MANAGER))
    bin = GST_BIN (gst_object_get_parent (GST_OBJECT_CAST (bin)));
  
  return bin;
}