gstreamer/gst/gstutils.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gstutils.c: Utility functions: gtk_get_property stuff, etc.
 *
 * 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.
 */

#include <stdio.h>
#include <string.h>

#include "gst_private.h"
#include "gstutils.h"
#include "gsturitype.h"
#include "gstinfo.h"
#include "gst-i18n-lib.h"


/**
 * gst_util_dump_mem:
 * @mem: a pointer to the memory to dump
 * @size: the size of the memory block to dump
 *
 * Dumps the memory block into a hex representation. Useful for debugging.
 */
void
gst_util_dump_mem (const guchar * mem, guint size)
{
  guint i, j;
  GString *string = g_string_sized_new (50);
  GString *chars = g_string_sized_new (18);

  i = j = 0;
  while (i < size) {
    if (g_ascii_isprint (mem[i]))
      g_string_append_printf (chars, "%c", mem[i]);
    else
      g_string_append_printf (chars, ".");

    g_string_append_printf (string, "%02x ", mem[i]);

    j++;
    i++;

    if (j == 16 || i == size) {
      g_print ("%08x (%p): %-48.48s %-16.16s\n", i - j, mem + i - j,
          string->str, chars->str);
      g_string_set_size (string, 0);
      g_string_set_size (chars, 0);
      j = 0;
    }
  }
  g_string_free (string, TRUE);
  g_string_free (chars, TRUE);
}


/**
 * gst_util_set_value_from_string:
 * @value: the value to set
 * @value_str: the string to get the value from
 *
 * Converts the string to the type of the value and
 * sets the value with it.
 */
void
gst_util_set_value_from_string (GValue * value, const gchar * value_str)
{

  g_return_if_fail (value != NULL);
  g_return_if_fail (value_str != NULL);

  GST_CAT_DEBUG (GST_CAT_PARAMS, "parsing '%s' to type %s", value_str,
      g_type_name (G_VALUE_TYPE (value)));

  switch (G_VALUE_TYPE (value)) {
    case G_TYPE_STRING:
      g_value_set_string (value, g_strdup (value_str));
      break;
    case G_TYPE_ENUM:
    case G_TYPE_INT:{
      gint i;

      sscanf (value_str, "%d", &i);
      g_value_set_int (value, i);
      break;
    }
    case G_TYPE_UINT:{
      guint i;

      sscanf (value_str, "%u", &i);
      g_value_set_uint (value, i);
      break;
    }
    case G_TYPE_LONG:{
      glong i;

      sscanf (value_str, "%ld", &i);
      g_value_set_long (value, i);
      break;
    }
    case G_TYPE_ULONG:{
      gulong i;

      sscanf (value_str, "%lu", &i);
      g_value_set_ulong (value, i);
      break;
    }
    case G_TYPE_BOOLEAN:{
      gboolean i = FALSE;

      if (!strncmp ("true", value_str, 4))
        i = TRUE;
      g_value_set_boolean (value, i);
      break;
    }
    case G_TYPE_CHAR:{
      gchar i;

      sscanf (value_str, "%c", &i);
      g_value_set_char (value, i);
      break;
    }
    case G_TYPE_UCHAR:{
      guchar i;

      sscanf (value_str, "%c", &i);
      g_value_set_uchar (value, i);
      break;
    }
    case G_TYPE_FLOAT:{
      gfloat i;

      sscanf (value_str, "%f", &i);
      g_value_set_float (value, i);
      break;
    }
    case G_TYPE_DOUBLE:{
      gfloat i;

      sscanf (value_str, "%g", &i);
      g_value_set_double (value, (gdouble) i);
      break;
    }
    default:
      break;
  }
}

/**
 * gst_util_set_object_arg:
 * @object: the object to set the argument of
 * @name: the name of the argument to set
 * @value: the string value to set
 *
 * Convertes the string value to the type of the objects argument and
 * sets the argument with it.
 */
void
gst_util_set_object_arg (GObject * object, const gchar * name,
    const gchar * value)
{
  if (name && value) {
    GParamSpec *paramspec;

    paramspec =
        g_object_class_find_property (G_OBJECT_GET_CLASS (object), name);

    if (!paramspec) {
      return;
    }

    GST_DEBUG ("paramspec->flags is %d, paramspec->value_type is %d",
        paramspec->flags, (gint) paramspec->value_type);

    if (paramspec->flags & G_PARAM_WRITABLE) {
      switch (paramspec->value_type) {
        case G_TYPE_STRING:
          g_object_set (G_OBJECT (object), name, value, NULL);
          break;
        case G_TYPE_ENUM:
        case G_TYPE_INT:{
          gint i;

          sscanf (value, "%d", &i);
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_UINT:{
          guint i;

          sscanf (value, "%u", &i);
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_LONG:{
          glong i;

          sscanf (value, "%ld", &i);
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_ULONG:{
          gulong i;

          sscanf (value, "%lu", &i);
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_BOOLEAN:{
          gboolean i = FALSE;

          if (!g_ascii_strncasecmp ("true", value, 4))
            i = TRUE;
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_CHAR:{
          gchar i;

          sscanf (value, "%c", &i);
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_UCHAR:{
          guchar i;

          sscanf (value, "%c", &i);
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_FLOAT:{
          gfloat i;

          sscanf (value, "%f", &i);
          g_object_set (G_OBJECT (object), name, i, NULL);
          break;
        }
        case G_TYPE_DOUBLE:{
          gfloat i;

          sscanf (value, "%g", &i);
          g_object_set (G_OBJECT (object), name, (gdouble) i, NULL);
          break;
        }
        default:
          if (G_IS_PARAM_SPEC_ENUM (paramspec)) {
            gint i;

            sscanf (value, "%d", &i);
            g_object_set (G_OBJECT (object), name, i, NULL);
          } else if (paramspec->value_type == GST_TYPE_URI) {
            g_object_set (G_OBJECT (object), name, value, NULL);
          }
          break;
      }
    }
  }
}

/* -----------------------------------------------------
 *
 *  The following code will be moved out of the main
 * gstreamer library someday.
 */

#include "gstpad.h"

static void
string_append_indent (GString * str, gint count)
{
  gint xx;

  for (xx = 0; xx < count; xx++)
    g_string_append_c (str, ' ');
}

/**
 * gst_print_pad_caps:
 * @buf: the buffer to print the caps in
 * @indent: initial indentation
 * @pad: the pad to print the caps from
 *
 * Write the pad capabilities in a human readable format into
 * the given GString.
 */
void
gst_print_pad_caps (GString * buf, gint indent, GstPad * pad)
{
  GstRealPad *realpad;
  GstCaps *caps;

  realpad = GST_PAD_REALIZE (pad);
  caps = realpad->caps;

  if (!caps) {
    string_append_indent (buf, indent);
    g_string_printf (buf, "%s:%s has no capabilities",
        GST_DEBUG_PAD_NAME (pad));
  } else {
    char *s;

    s = gst_caps_to_string (caps);
    g_string_append (buf, s);
    g_free (s);
  }
}

/**
 * gst_print_element_args:
 * @buf: the buffer to print the args in
 * @indent: initial indentation
 * @element: the element to print the args of
 *
 * Print the element argument in a human readable format in the given
 * GString.
 */
void
gst_print_element_args (GString * buf, gint indent, GstElement * element)
{
  guint width;
  GValue value = { 0, };        /* the important thing is that value.type = 0 */
  gchar *str = NULL;
  GParamSpec *spec, **specs, **walk;

  specs = g_object_class_list_properties (G_OBJECT_GET_CLASS (element), NULL);

  width = 0;
  for (walk = specs; *walk; walk++) {
    spec = *walk;
    if (width < strlen (spec->name))
      width = strlen (spec->name);
  }

  for (walk = specs; *walk; walk++) {
    spec = *walk;

    if (spec->flags & G_PARAM_READABLE) {
      g_value_init (&value, G_PARAM_SPEC_VALUE_TYPE (spec));
      g_object_get_property (G_OBJECT (element), spec->name, &value);
      str = g_strdup_value_contents (&value);
      g_value_unset (&value);
    } else {
      str = g_strdup ("Parameter not readable.");
    }

    string_append_indent (buf, indent);
    g_string_append (buf, spec->name);
    string_append_indent (buf, 2 + width - strlen (spec->name));
    g_string_append (buf, str);
    g_string_append_c (buf, '\n');

    g_free (str);
  }

  g_free (specs);
}

GstFlowReturn
gst_element_abort_preroll (GstElement * element)
{
  GstFlowReturn result = GST_FLOW_OK;

  /* grab state change lock */
  GST_STATE_LOCK (element);
  /* if we are going to PAUSED, we can abort the state change */
  if (GST_STATE_TRANSITION (element) == GST_STATE_READY_TO_PAUSED) {
    gst_element_abort_state (GST_ELEMENT (element));
  }
  GST_STATE_UNLOCK (element);

  return result;
}

/* call with stream lock held */
GstFlowReturn
gst_element_finish_preroll (GstElement * element, GMutex * streamlock)
{
  GstFlowReturn result = GST_FLOW_OK;

  /* grab state change lock */
  GST_STATE_LOCK (element);
  /* if we are going to PAUSED, we can commit the state change */
  if (GST_STATE_TRANSITION (element) == GST_STATE_READY_TO_PAUSED) {
    gst_element_commit_state (GST_ELEMENT (element));
  }
  /* if we are paused we need to wait for playing to continue */
  if (GST_STATE (element) == GST_STATE_PAUSED) {
    GST_CAT_DEBUG (GST_CAT_STATES,
        "element %s wants to finish preroll", GST_ELEMENT_NAME (element));


    /* FIXME, release streaming lock? */
    if (streamlock)
      g_mutex_unlock (streamlock);

    /* here we wait for the next state change */
    do {
      GST_CAT_DEBUG (GST_CAT_STATES, "waiting for next state change");

      GST_STATE_WAIT (element);
    }
    while (GST_STATE (element) == GST_STATE_PAUSED);

    if (streamlock)
      g_mutex_lock (streamlock);
    /* check if we got playing */
    if (GST_STATE (element) != GST_STATE_PLAYING) {
      /* not playing, we can't accept the buffer */
      result = GST_FLOW_WRONG_STATE;
    }
    GST_CAT_DEBUG (GST_CAT_STATES, "done preroll");
  }
  GST_STATE_UNLOCK (element);

  return result;
}

/**
 * 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.
 *
 * Retrieves a pad template from @element that is compatible with @compattempl.
 * Pads from compatible templates can be linked together.
 *
 * Returns: a compatible #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;
  GstElementClass *class;

  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);

  class = GST_ELEMENT_GET_CLASS (element);

  padlist = gst_element_class_get_pad_template_list (class);

  GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
      "Looking for a suitable pad template in %s out of %d templates...",
      GST_ELEMENT_NAME (element), g_list_length (padlist));

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

    /* Ignore name
     * Ignore presence
     * Check direction (must be opposite)
     * Check caps
     */
    GST_CAT_LOG (GST_CAT_CAPS,
        "checking pad template %s", padtempl->name_template);
    if (padtempl->direction != compattempl->direction) {
      GST_CAT_DEBUG (GST_CAT_CAPS,
          "compatible direction: found %s pad template \"%s\"",
          padtempl->direction == GST_PAD_SRC ? "src" : "sink",
          padtempl->name_template);

      intersection = gst_caps_intersect (GST_PAD_TEMPLATE_CAPS (compattempl),
          GST_PAD_TEMPLATE_CAPS (padtempl));

      GST_CAT_DEBUG (GST_CAT_CAPS, "caps are %scompatible",
          (intersection ? "" : "not "));

      if (!gst_caps_is_empty (intersection))
        newtempl = padtempl;
      gst_caps_unref (intersection);
      if (newtempl)
        break;
    }

    padlist = g_list_next (padlist);
  }
  if (newtempl)
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
        "Returning new pad template %p", newtempl);
  else
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "No compatible pad template found");

  return newtempl;
}

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_get_pad_from_template:
 * @element: a #GstElement.
 * @templ: a #GstPadTemplate belonging to @element.
 *
 * Gets a pad from @element described by @templ. If the presence of @templ is
 * #GST_PAD_REQUEST, requests a new pad. Can return %NULL for #GST_PAD_SOMETIMES
 * templates.
 *
 * Returns: the #GstPad, or NULL if one could not be found or created.
 */
static GstPad *
gst_element_get_pad_from_template (GstElement * element, GstPadTemplate * templ)
{
  GstPad *ret = NULL;
  GstPadPresence presence;

  /* If this function is ever exported, we need check the validity of `element'
   * and `templ', and to make sure the template actually belongs to the
   * element. */

  presence = GST_PAD_TEMPLATE_PRESENCE (templ);

  switch (presence) {
    case GST_PAD_ALWAYS:
    case GST_PAD_SOMETIMES:
      ret = gst_element_get_static_pad (element, templ->name_template);
      if (!ret && presence == GST_PAD_ALWAYS)
        g_warning
            ("Element %s has an ALWAYS template %s, but no pad of the same name",
            GST_OBJECT_NAME (element), templ->name_template);
      break;

    case GST_PAD_REQUEST:
      ret = gst_element_request_pad (element, templ, NULL);
      break;
  }

  return ret;
}

/**
 * gst_element_request_compatible_pad:
 * @element: a #GstElement.
 * @templ: the #GstPadTemplate to which the new pad should be able to link.
 *
 * Requests a pad from @element. The returned pad should be unlinked and
 * compatible with @templ. Might return an existing pad, or request a new one.
 *
 * Returns: a #GstPad, or %NULL if one could not be found or created.
 */
GstPad *
gst_element_request_compatible_pad (GstElement * element,
    GstPadTemplate * templ)
{
  GstPadTemplate *templ_new;
  GstPad *pad = NULL;

  g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
  g_return_val_if_fail (GST_IS_PAD_TEMPLATE (templ), NULL);

  /* FIXME: should really loop through the templates, testing each for
   *      compatibility and pad availability. */
  templ_new = gst_element_get_compatible_pad_template (element, templ);
  if (templ_new)
    pad = gst_element_get_pad_from_template (element, templ_new);

  /* This can happen for non-request pads. No need to unref. */
  if (pad && GST_PAD_PEER (pad))
    pad = 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. 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 one cannot be
 * found.
 */
GstPad *
gst_element_get_compatible_pad_filtered (GstElement * element, GstPad * pad,
    const GstCaps * filtercaps)
{
  const GList *pads;
  GstPadTemplate *templ;
  GstCaps *templcaps;
  GstPad *foundpad = NULL;

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

  GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
      "finding pad in %s compatible with %s:%s and filter %" GST_PTR_FORMAT,
      GST_ELEMENT_NAME (element), GST_DEBUG_PAD_NAME (pad), filtercaps);

  /* 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);

    GST_CAT_LOG (GST_CAT_ELEMENT_PADS, "examing pad %s:%s",
        GST_DEBUG_PAD_NAME (current));
    if (GST_PAD_PEER (current) == NULL &&
        gst_pad_can_link_filtered (pad, current, filtercaps)) {
      GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
          "found existing unlinked pad %s:%s", GST_DEBUG_PAD_NAME (current));
      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 */
  templcaps = GST_PAD_CAPS (pad);
  if (filtercaps != NULL) {
    GstCaps *temp;

    temp = gst_caps_intersect (filtercaps, templcaps);
    gst_caps_unref (templcaps);
    templcaps = temp;
  }

  templ = gst_pad_template_new ((gchar *) GST_PAD_NAME (pad),
      GST_PAD_DIRECTION (pad), GST_PAD_ALWAYS, templcaps);
  foundpad = gst_element_request_compatible_pad (element, templ);
  gst_object_unref (GST_OBJECT (templ));

  if (foundpad) {
    GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
        "found existing request pad %s:%s", GST_DEBUG_PAD_NAME (foundpad));
    return foundpad;
  }

  GST_CAT_INFO_OBJECT (GST_CAT_ELEMENT_PADS, element,
      "Could not find a compatible pad to link to %s:%s",
      GST_DEBUG_PAD_NAME (pad));
  return NULL;
}



/**
 * 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 one
 * could not be found.
 */
GstPad *
gst_element_get_compatible_pad (GstElement * element, GstPad * pad)
{
  return gst_element_get_compatible_pad_filtered (element, pad, NULL);
}

/**
 * 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;34mNULL\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;35;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 "";
}

/**
 * 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 pad.
 * @dest: the #GstElement containing the destination pad.
 * @destpadname: the name of the #GstPad in destination element or NULL for any pad.
 * @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, FALSE otherwise.
 */
GstPadLinkReturn
gst_element_link_pads_filtered (GstElement * src, const gchar * srcpadname,
    GstElement * dest, const gchar * destpadname, const GstCaps * filtercaps)
{
  const GList *srcpads, *destpads, *srctempls, *desttempls, *l;
  GstPad *srcpad, *destpad;
  GstPadTemplate *srctempl, *desttempl;
  GstElementClass *srcclass, *destclass;

  /* checks */
  g_return_val_if_fail (GST_IS_ELEMENT (src), FALSE);
  g_return_val_if_fail (GST_IS_ELEMENT (dest), FALSE);

  srcclass = GST_ELEMENT_GET_CLASS (src);
  destclass = GST_ELEMENT_GET_CLASS (dest);

  GST_CAT_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_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "no pad %s:%s",
          GST_ELEMENT_NAME (src), srcpadname);
      return FALSE;
    } else {
      if (!(GST_PAD_DIRECTION (srcpad) == GST_PAD_SRC)) {
        GST_CAT_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_CAT_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_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "no pad %s:%s",
          GST_ELEMENT_NAME (dest), destpadname);
      return FALSE;
    } else {
      if (!(GST_PAD_DIRECTION (destpad) == GST_PAD_SINK)) {
        GST_CAT_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_CAT_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_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
        "looping through allowed src and dest pads");
    do {
      GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "trying src pad %s:%s",
          GST_DEBUG_PAD_NAME (srcpad));
      if ((GST_PAD_DIRECTION (srcpad) == GST_PAD_SRC) &&
          (GST_PAD_PEER (srcpad) == NULL)) {
        GstPad *temp = destpadname ? destpad :
            gst_element_get_compatible_pad_filtered (dest, srcpad,
            filtercaps);

        if (temp
            && gst_pad_link_filtered (srcpad, temp,
                filtercaps) == GST_PAD_LINK_OK) {
          GST_CAT_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_CAT_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_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "trying dest pad %s:%s",
          GST_DEBUG_PAD_NAME (destpad));
      if ((GST_PAD_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_PAD_LINK_OK) {
          GST_CAT_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_CAT_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_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
      "we might have request pads on both sides, checking...");
  srctempls = gst_element_class_get_pad_template_list (srcclass);
  desttempls = gst_element_class_get_pad_template_list (destclass);

  if (srctempls && desttempls) {
    while (srctempls) {
      srctempl = (GstPadTemplate *) srctempls->data;
      if (srctempl->presence == GST_PAD_REQUEST) {
        for (l = desttempls; l; l = l->next) {
          desttempl = (GstPadTemplate *) l->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_PAD_LINK_OK) {
                GST_CAT_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;
              }
              /* it failed, so we release the request pads */
              gst_element_release_request_pad (src, srcpad);
              gst_element_release_request_pad (dest, destpad);
            }
          }
        }
      }
      srctempls = srctempls->next;
    }
  }

  GST_CAT_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 @src to @dest, filtered by @filtercaps. The link must be from source to
 * destination; the other direction will not be tried. The function looks for
 * existing pads that aren't linked yet. It will request new pads if necessary.
 * If multiple links are possible, only one is established.
 *
 * Returns: TRUE if the elements could be linked, FALSE otherwise.
 */
GstPadLinkReturn
gst_element_link_filtered (GstElement * src, GstElement * dest,
    const 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.
 */
GstPadLinkReturn
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 @src to @dest with no filter caps. See gst_element_link_filtered() for
 * more information.
 *
 * Returns: TRUE if the elements could be linked, FALSE otherwise.
 */
GstPadLinkReturn
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, FALSE otherwise.
 */
GstPadLinkReturn
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_WARNING_OBJECT (src, "source element has no pad \"%s\"", srcpadname);
    return;
  }
  destpad = gst_element_get_pad (dest, destpadname);
  if (srcpad == NULL) {
    GST_WARNING_OBJECT (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_CAT_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 (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);
  }
}

/**
 * gst_pad_can_link_filtered:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 * @filtercaps: the filter #GstCaps.
 *
 * Checks if the source pad and the sink pad can be linked when constrained
 * by the given filter caps. Both @srcpad and @sinkpad must be unlinked.
 *
 * Returns: TRUE if the pads can be linked, FALSE otherwise.
 */
gboolean
gst_pad_can_link_filtered (GstPad * srcpad, GstPad * sinkpad,
    const GstCaps * filtercaps)
{
  GstRealPad *realsrc, *realsink;

  /* FIXME This function is gross.  It's almost a direct copy of
   * gst_pad_link_filtered().  Any decent programmer would attempt
   * to merge the two functions, which I will do some day. --ds
   */

  /* generic checks */
  g_return_val_if_fail (srcpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (srcpad), FALSE);
  g_return_val_if_fail (sinkpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (sinkpad), FALSE);

  GST_CAT_INFO (GST_CAT_PADS, "trying to link %s:%s and %s:%s",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  /* now we need to deal with the real/ghost stuff */
  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);

  if ((GST_PAD (realsrc) != srcpad) || (GST_PAD (realsink) != sinkpad)) {
    GST_CAT_INFO (GST_CAT_PADS, "*actually* linking %s:%s and %s:%s",
        GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));
  }
  /* FIXME: shouldn't we convert this to g_return_val_if_fail? */
  if (GST_RPAD_PEER (realsrc) != NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Real source pad %s:%s has a peer, failed",
        GST_DEBUG_PAD_NAME (realsrc));
    return FALSE;
  }
  if (GST_RPAD_PEER (realsink) != NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Real sink pad %s:%s has a peer, failed",
        GST_DEBUG_PAD_NAME (realsink));
    return FALSE;
  }
  if (GST_PAD_PARENT (realsrc) == NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Real src pad %s:%s has no parent, failed",
        GST_DEBUG_PAD_NAME (realsrc));
    return FALSE;
  }
  if (GST_PAD_PARENT (realsink) == NULL) {
    GST_CAT_INFO (GST_CAT_PADS, "Real sink pad %s:%s has no parent, failed",
        GST_DEBUG_PAD_NAME (realsrc));
    return FALSE;
  }

  g_return_val_if_fail (realsrc != NULL, GST_PAD_LINK_REFUSED);
  g_return_val_if_fail (realsink != NULL, GST_PAD_LINK_REFUSED);

  return TRUE;
}

/**
 * gst_pad_can_link:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 *
 * Checks if the source pad and the sink pad can be linked.
 *
 * Returns: TRUE if the pads can be linked, FALSE otherwise.
 */
gboolean
gst_pad_can_link (GstPad * srcpad, GstPad * sinkpad)
{
  return gst_pad_can_link_filtered (srcpad, sinkpad, NULL);
}

/**
 * gst_object_default_error:
 * @object: a #GObject that signalled the error.
 * @orig: the #GstObject that initiated the error.
 * @error: the GError.
 * @debug: an additional debug information string, or NULL.
 *
 * A default error function.
 *
 * The default handler will simply print the error string using g_print.
 */
void
gst_object_default_error (GstObject * source, GError * error, gchar * debug)
{
  gchar *name = gst_object_get_path_string (source);

  g_print (_("ERROR: from element %s: %s\n"), name, error->message);
  if (debug)
    g_print (_("Additional debug info:\n%s\n"), debug);

  g_free (name);
}

/**
 * gst_bin_add_many:
 * @bin: the bin to add the elements to
 * @element_1: the first element to add to the bin
 * @...: additional elements to add to the bin
 *
 * Adds a NULL-terminated list of elements to a bin.  This function is
 * equivalent to calling #gst_bin_add() for each member of the list.
 */
void
gst_bin_add_many (GstBin * bin, GstElement * element_1, ...)
{
  va_list args;

  g_return_if_fail (GST_IS_BIN (bin));
  g_return_if_fail (GST_IS_ELEMENT (element_1));

  va_start (args, element_1);

  while (element_1) {
    gst_bin_add (bin, element_1);

    element_1 = va_arg (args, GstElement *);
  }

  va_end (args);
}

/**
 * gst_bin_remove_many:
 * @bin: the bin to remove the elements from
 * @element_1: the first element to remove from the bin
 * @...: NULL-terminated list of elements to remove from the bin
 *
 * Remove a list of elements from a bin. This function is equivalent
 * to calling #gst_bin_remove with each member of the list.
 */
void
gst_bin_remove_many (GstBin * bin, GstElement * element_1, ...)
{
  va_list args;

  g_return_if_fail (GST_IS_BIN (bin));
  g_return_if_fail (GST_IS_ELEMENT (element_1));

  va_start (args, element_1);

  while (element_1) {
    gst_bin_remove (bin, element_1);

    element_1 = va_arg (args, GstElement *);
  }

  va_end (args);
}