gstreamer/gst/gstpad.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gstpad.c: Pads for linking elements together
 *
 * 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.
 */
/**
 * SECTION:gstpad
 * @short_description: Object contained by elements that allows links to
 *                     other elements
 * @see_also: #GstPadTemplate, #GstElement, #GstEvent
 *
 * A #GstElement is linked to other elements via "pads", which are extremely
 * light-weight generic link points.
 * After two pads are retrieved from an element with gst_element_get_pad(),
 * the pads can be link with gst_pad_link(). (For quick links,
 * you can also use gst_element_link(), which will make the obvious
 * link for you if it's straightforward.)
 *
 * Pads are typically created from a #GstPadTemplate with
 * gst_pad_new_from_template().
 *
 * Pads have #GstCaps attached to it to describe the media type they are
 * capable of dealing with.  gst_pad_get_caps() and gst_pad_set_caps() are
 * used to manipulate the caps of the pads.
 * Pads created from a pad template cannot set capabilities that are
 * incompatible with the pad template capabilities.
 *
 * Pads without pad templates can be created with gst_pad_new(),
 * which takes a direction and a name as an argument.  If the name is NULL,
 * then a guaranteed unique name will be assigned to it.
 *
 * gst_pad_get_parent() will retrieve the #GstElement that owns the pad.
 *
 * A #GstElement creating a pad will typically use the various
 * gst_pad_set_*_function() calls to register callbacks for various events
 * on the pads.
 *
 * GstElements will use gst_pad_push() and gst_pad_pull_range() to push out
 * or pull in a buffer.
 *
 * To send a #GstEvent on a pad, use gst_pad_send_event() and
 * gst_pad_push_event().
 *
 * Last reviewed on 2006-07-06 (0.10.9)
 */

#include "gst_private.h"

#include "gstpad.h"
#include "gstpadtemplate.h"
#include "gstenumtypes.h"
#include "gstmarshal.h"
#include "gstutils.h"
#include "gstinfo.h"
#include "gsterror.h"
#include "gstvalue.h"
#include "glib-compat-private.h"

GST_DEBUG_CATEGORY_STATIC (debug_dataflow);
#define GST_CAT_DEFAULT GST_CAT_PADS

/* Pad signals and args */
enum
{
  PAD_LINKED,
  PAD_UNLINKED,
  /* FILL ME */
  LAST_SIGNAL
};

enum
{
  PAD_PROP_0,
  PAD_PROP_CAPS,
  PAD_PROP_DIRECTION,
  PAD_PROP_TEMPLATE,
  /* FILL ME */
};

#define GST_PAD_GET_PRIVATE(obj)  \
   (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_PAD, GstPadPrivate))

/* we have a pending and an active event on the pad. On source pads only the
 * active event is used. On sinkpads, events are copied to the pending entry and
 * moved to the active event when the eventfunc returned TRUE. */
typedef struct
{
  GstEvent *pending;
  GstEvent *event;
} PadEvent;

struct _GstPadPrivate
{
  PadEvent events[GST_EVENT_MAX_STICKY];

  gint using;
  gint probe_cookie;
};

typedef struct
{
  GHook hook;
  guint cookie;
} GstProbe;

#define PROBE_COOKIE(h) (((GstProbe *)(h))->cookie)

typedef struct
{
  GstPad *pad;
  GstProbeType mask;
  gpointer type_data;
  GstProbeReturn ret;
  gboolean pass;
  guint cookie;
} ProbeMarshall;

static void gst_pad_dispose (GObject * object);
static void gst_pad_finalize (GObject * object);
static void gst_pad_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_pad_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);

static GstCaps *gst_pad_get_caps_unlocked (GstPad * pad, GstCaps * filter);
static void gst_pad_set_pad_template (GstPad * pad, GstPadTemplate * templ);
static gboolean gst_pad_activate_default (GstPad * pad);
static gboolean gst_pad_acceptcaps_default (GstPad * pad, GstCaps * caps);
static void gst_pad_fixate_caps_default (GstPad * pad, GstCaps * caps);
static GstFlowReturn gst_pad_chain_list_default (GstPad * pad,
    GstBufferList * list);

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

static GParamSpec *pspec_caps = NULL;

/* quarks for probe signals */
static GQuark buffer_quark;
static GQuark buffer_list_quark;
static GQuark event_quark;

typedef struct
{
  const gint ret;
  const gchar *name;
  GQuark quark;
} GstFlowQuarks;

static GstFlowQuarks flow_quarks[] = {
  {GST_FLOW_CUSTOM_SUCCESS, "custom-success", 0},
  {GST_FLOW_RESEND, "resend", 0},
  {GST_FLOW_OK, "ok", 0},
  {GST_FLOW_NOT_LINKED, "not-linked", 0},
  {GST_FLOW_WRONG_STATE, "wrong-state", 0},
  {GST_FLOW_UNEXPECTED, "unexpected", 0},
  {GST_FLOW_NOT_NEGOTIATED, "not-negotiated", 0},
  {GST_FLOW_ERROR, "error", 0},
  {GST_FLOW_NOT_SUPPORTED, "not-supported", 0},
  {GST_FLOW_CUSTOM_ERROR, "custom-error", 0}
};

/**
 * gst_flow_get_name:
 * @ret: a #GstFlowReturn to get the name of.
 *
 * Gets a string representing the given flow return.
 *
 * Returns: a static string with the name of the flow return.
 */
const gchar *
gst_flow_get_name (GstFlowReturn ret)
{
  gint i;

  ret = CLAMP (ret, GST_FLOW_CUSTOM_ERROR, GST_FLOW_CUSTOM_SUCCESS);

  for (i = 0; i < G_N_ELEMENTS (flow_quarks); i++) {
    if (ret == flow_quarks[i].ret)
      return flow_quarks[i].name;
  }
  return "unknown";
}

/**
 * gst_flow_to_quark:
 * @ret: a #GstFlowReturn to get the quark of.
 *
 * Get the unique quark for the given GstFlowReturn.
 *
 * Returns: the quark associated with the flow return or 0 if an
 * invalid return was specified.
 */
GQuark
gst_flow_to_quark (GstFlowReturn ret)
{
  gint i;

  ret = CLAMP (ret, GST_FLOW_CUSTOM_ERROR, GST_FLOW_CUSTOM_SUCCESS);

  for (i = 0; i < G_N_ELEMENTS (flow_quarks); i++) {
    if (ret == flow_quarks[i].ret)
      return flow_quarks[i].quark;
  }
  return 0;
}

#define _do_init \
{ \
  gint i; \
  \
  buffer_quark = g_quark_from_static_string ("buffer"); \
  buffer_list_quark = g_quark_from_static_string ("bufferlist"); \
  event_quark = g_quark_from_static_string ("event"); \
  \
  for (i = 0; i < G_N_ELEMENTS (flow_quarks); i++) {			\
    flow_quarks[i].quark = g_quark_from_static_string (flow_quarks[i].name); \
  } \
  \
  GST_DEBUG_CATEGORY_INIT (debug_dataflow, "GST_DATAFLOW", \
      GST_DEBUG_BOLD | GST_DEBUG_FG_GREEN, "dataflow inside pads"); \
}

G_DEFINE_TYPE_WITH_CODE (GstPad, gst_pad, GST_TYPE_OBJECT, _do_init);

static void
gst_pad_class_init (GstPadClass * klass)
{
  GObjectClass *gobject_class;
  GstObjectClass *gstobject_class;

  gobject_class = G_OBJECT_CLASS (klass);
  gstobject_class = GST_OBJECT_CLASS (klass);

  g_type_class_add_private (klass, sizeof (GstPadPrivate));

  parent_class = g_type_class_peek_parent (klass);

  gobject_class->dispose = gst_pad_dispose;
  gobject_class->finalize = gst_pad_finalize;
  gobject_class->set_property = gst_pad_set_property;
  gobject_class->get_property = gst_pad_get_property;

  /**
   * GstPad::linked:
   * @pad: the pad that emitted the signal
   * @peer: the peer pad that has been connected
   *
   * Signals that a pad has been linked to the peer pad.
   */
  gst_pad_signals[PAD_LINKED] =
      g_signal_new ("linked", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
      G_STRUCT_OFFSET (GstPadClass, linked), NULL, NULL,
      gst_marshal_VOID__OBJECT, G_TYPE_NONE, 1, GST_TYPE_PAD);
  /**
   * GstPad::unlinked:
   * @pad: the pad that emitted the signal
   * @peer: the peer pad that has been disconnected
   *
   * Signals that a pad has been unlinked from the peer pad.
   */
  gst_pad_signals[PAD_UNLINKED] =
      g_signal_new ("unlinked", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
      G_STRUCT_OFFSET (GstPadClass, unlinked), NULL, NULL,
      gst_marshal_VOID__OBJECT, G_TYPE_NONE, 1, GST_TYPE_PAD);

  pspec_caps = g_param_spec_boxed ("caps", "Caps",
      "The capabilities of the pad", GST_TYPE_CAPS,
      G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);
  g_object_class_install_property (gobject_class, PAD_PROP_CAPS, pspec_caps);

  g_object_class_install_property (gobject_class, PAD_PROP_DIRECTION,
      g_param_spec_enum ("direction", "Direction", "The direction of the pad",
          GST_TYPE_PAD_DIRECTION, GST_PAD_UNKNOWN,
          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_STRINGS));

  /* FIXME, Make G_PARAM_CONSTRUCT_ONLY when we fix ghostpads. */
  g_object_class_install_property (gobject_class, PAD_PROP_TEMPLATE,
      g_param_spec_object ("template", "Template",
          "The GstPadTemplate of this pad", GST_TYPE_PAD_TEMPLATE,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  gstobject_class->path_string_separator = ".";

  /* Register common function pointer descriptions */
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_activate_default);
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_event_default);
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_get_query_types_default);
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_query_default);
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_iterate_internal_links_default);
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_acceptcaps_default);
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_chain_list_default);
  GST_DEBUG_REGISTER_FUNCPTR (gst_pad_fixate_caps_default);
}

static void
gst_pad_init (GstPad * pad)
{
  pad->priv = GST_PAD_GET_PRIVATE (pad);

  GST_PAD_DIRECTION (pad) = GST_PAD_UNKNOWN;

  GST_PAD_ACTIVATEFUNC (pad) = gst_pad_activate_default;
  GST_PAD_EVENTFUNC (pad) = gst_pad_event_default;
  GST_PAD_QUERYTYPEFUNC (pad) = gst_pad_get_query_types_default;
  GST_PAD_QUERYFUNC (pad) = gst_pad_query_default;
  GST_PAD_ITERINTLINKFUNC (pad) = gst_pad_iterate_internal_links_default;
  GST_PAD_ACCEPTCAPSFUNC (pad) = gst_pad_acceptcaps_default;
  GST_PAD_FIXATECAPSFUNC (pad) = gst_pad_fixate_caps_default;
  GST_PAD_CHAINLISTFUNC (pad) = gst_pad_chain_list_default;

  GST_PAD_SET_FLUSHING (pad);

  g_static_rec_mutex_init (&pad->stream_rec_lock);

  pad->block_cond = g_cond_new ();

  g_hook_list_init (&pad->probes, sizeof (GstProbe));
}

/* called when setting the pad inactive. It removes all sticky events from
 * the pad */
static void
clear_events (PadEvent events[])
{
  guint i;

  for (i = 0; i < GST_EVENT_MAX_STICKY; i++) {
    gst_event_replace (&events[i].event, NULL);
    gst_event_replace (&events[i].pending, NULL);
  }
}

/* The sticky event with @idx from the srcpad is copied to the
 * pending event on the sinkpad (when different).
 * This function applies the pad offsets in case of segment events.
 * This will make sure that we send the event to the sinkpad event
 * function when the next buffer of event arrives.
 * Should be called with the OBJECT lock of both pads.
 * This function returns TRUE when there is a pending event on the
 * sinkpad */
static gboolean
replace_event (GstPad * srcpad, GstPad * sinkpad, guint idx)
{
  PadEvent *srcev, *sinkev;
  GstEvent *event;
  gboolean pending = FALSE;

  srcev = &srcpad->priv->events[idx];

  if ((event = srcev->event)) {
    sinkev = &sinkpad->priv->events[idx];

    switch (GST_EVENT_TYPE (event)) {
      case GST_EVENT_SEGMENT:
      {
        GstSegment segment;
        gint64 offset;

        offset = srcpad->offset + sinkpad->offset;
        if (offset != 0) {
          gst_event_copy_segment (event, &segment);
          /* adjust the base time. FIXME, check negative times, try to tweak the
           * start to do clipping on negative times */
          segment.base += offset;
          /* make a new event from the updated segment */
          event = gst_event_new_segment (&segment);
        }
        break;
      }
      default:
        break;
    }
    if (sinkev->event != event) {
      /* put in the pending entry when different */
      gst_event_replace (&sinkev->pending, event);
      pending = TRUE;
    }
  }
  return pending;
}


static void
prepare_event_update (GstPad * srcpad, GstPad * sinkpad)
{
  gboolean pending;
  gint i;

  /* make sure we push the events from the source to this new peer, for this we
   * copy the events on the sinkpad and mark EVENTS_PENDING */
  pending = FALSE;
  for (i = 0; i < GST_EVENT_MAX_STICKY; i++)
    pending |= replace_event (srcpad, sinkpad, i);

  /* we had some new pending events, set our flag */
  if (pending)
    GST_OBJECT_FLAG_SET (sinkpad, GST_PAD_NEED_EVENTS);
}

/* should be called with the OBJECT_LOCK */
static GstCaps *
get_pad_caps (GstPad * pad)
{
  GstCaps *caps = NULL;
  GstEvent *event;
  guint idx;

  idx = GST_EVENT_STICKY_IDX_TYPE (GST_EVENT_CAPS);
  /* we can only use the caps when we have successfully send the caps
   * event to the event function and is thus in the active entry */
  if ((event = pad->priv->events[idx].event))
    gst_event_parse_caps (event, &caps);

  return caps;
}

static void
gst_pad_dispose (GObject * object)
{
  GstPad *pad = GST_PAD_CAST (object);
  GstPad *peer;

  GST_CAT_DEBUG_OBJECT (GST_CAT_REFCOUNTING, pad, "dispose");

  /* unlink the peer pad */
  if ((peer = gst_pad_get_peer (pad))) {
    /* window for MT unsafeness, someone else could unlink here
     * and then we call unlink with wrong pads. The unlink
     * function would catch this and safely return failed. */
    if (GST_PAD_IS_SRC (pad))
      gst_pad_unlink (pad, peer);
    else
      gst_pad_unlink (peer, pad);

    gst_object_unref (peer);
  }

  gst_pad_set_pad_template (pad, NULL);

  clear_events (pad->priv->events);

  g_hook_list_clear (&pad->probes);

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

static void
gst_pad_finalize (GObject * object)
{
  GstPad *pad = GST_PAD_CAST (object);
  GstTask *task;

  /* in case the task is still around, clean it up */
  if ((task = GST_PAD_TASK (pad))) {
    gst_task_join (task);
    GST_PAD_TASK (pad) = NULL;
    gst_object_unref (task);
  }

  g_static_rec_mutex_free (&pad->stream_rec_lock);
  g_cond_free (pad->block_cond);

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

static void
gst_pad_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  g_return_if_fail (GST_IS_PAD (object));

  switch (prop_id) {
    case PAD_PROP_DIRECTION:
      GST_PAD_DIRECTION (object) = g_value_get_enum (value);
      break;
    case PAD_PROP_TEMPLATE:
      gst_pad_set_pad_template (GST_PAD_CAST (object),
          (GstPadTemplate *) g_value_get_object (value));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_pad_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  g_return_if_fail (GST_IS_PAD (object));

  switch (prop_id) {
    case PAD_PROP_CAPS:
      GST_OBJECT_LOCK (object);
      g_value_set_boxed (value, get_pad_caps (GST_PAD_CAST (object)));
      GST_OBJECT_UNLOCK (object);
      break;
    case PAD_PROP_DIRECTION:
      g_value_set_enum (value, GST_PAD_DIRECTION (object));
      break;
    case PAD_PROP_TEMPLATE:
      g_value_set_object (value, GST_PAD_PAD_TEMPLATE (object));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

/**
 * gst_pad_new:
 * @name: the name of the new pad.
 * @direction: the #GstPadDirection of the pad.
 *
 * Creates a new pad with the given name in the given direction.
 * If name is NULL, a guaranteed unique name (across all pads)
 * will be assigned.
 * This function makes a copy of the name so you can safely free the name.
 *
 * Returns: (transfer full): a new #GstPad, or NULL in case of an error.
 *
 * MT safe.
 */
GstPad *
gst_pad_new (const gchar * name, GstPadDirection direction)
{
  return g_object_new (GST_TYPE_PAD,
      "name", name, "direction", direction, NULL);
}

/**
 * gst_pad_new_from_template:
 * @templ: the pad template to use
 * @name: the name of the element
 *
 * Creates a new pad with the given name from the given template.
 * If name is NULL, a guaranteed unique name (across all pads)
 * will be assigned.
 * This function makes a copy of the name so you can safely free the name.
 *
 * Returns: (transfer full): a new #GstPad, or NULL in case of an error.
 */
GstPad *
gst_pad_new_from_template (GstPadTemplate * templ, const gchar * name)
{
  g_return_val_if_fail (GST_IS_PAD_TEMPLATE (templ), NULL);

  return g_object_new (GST_TYPE_PAD,
      "name", name, "direction", templ->direction, "template", templ, NULL);
}

/**
 * gst_pad_new_from_static_template:
 * @templ: the #GstStaticPadTemplate to use
 * @name: the name of the element
 *
 * Creates a new pad with the given name from the given static template.
 * If name is NULL, a guaranteed unique name (across all pads)
 * will be assigned.
 * This function makes a copy of the name so you can safely free the name.
 *
 * Returns: (transfer full): a new #GstPad, or NULL in case of an error.
 */
GstPad *
gst_pad_new_from_static_template (GstStaticPadTemplate * templ,
    const gchar * name)
{
  GstPad *pad;
  GstPadTemplate *template;

  template = gst_static_pad_template_get (templ);
  pad = gst_pad_new_from_template (template, name);
  gst_object_unref (template);
  return pad;
}

/**
 * gst_pad_get_direction:
 * @pad: a #GstPad to get the direction of.
 *
 * Gets the direction of the pad. The direction of the pad is
 * decided at construction time so this function does not take
 * the LOCK.
 *
 * Returns: the #GstPadDirection of the pad.
 *
 * MT safe.
 */
GstPadDirection
gst_pad_get_direction (GstPad * pad)
{
  GstPadDirection result;

  /* PAD_UNKNOWN is a little silly but we need some sort of
   * error return value */
  g_return_val_if_fail (GST_IS_PAD (pad), GST_PAD_UNKNOWN);

  result = GST_PAD_DIRECTION (pad);

  return result;
}

static gboolean
gst_pad_activate_default (GstPad * pad)
{
  return gst_pad_activate_push (pad, TRUE);
}

static void
pre_activate (GstPad * pad, GstActivateMode new_mode)
{
  switch (new_mode) {
    case GST_ACTIVATE_PUSH:
    case GST_ACTIVATE_PULL:
      GST_OBJECT_LOCK (pad);
      GST_DEBUG_OBJECT (pad, "setting ACTIVATE_MODE %d, unset flushing",
          new_mode);
      GST_PAD_UNSET_FLUSHING (pad);
      GST_PAD_ACTIVATE_MODE (pad) = new_mode;
      GST_OBJECT_UNLOCK (pad);
      break;
    case GST_ACTIVATE_NONE:
      GST_OBJECT_LOCK (pad);
      GST_DEBUG_OBJECT (pad, "setting ACTIVATE_MODE NONE, set flushing");
      GST_PAD_SET_FLUSHING (pad);
      GST_PAD_ACTIVATE_MODE (pad) = new_mode;
      /* unlock blocked pads so element can resume and stop */
      GST_PAD_BLOCK_BROADCAST (pad);
      GST_OBJECT_UNLOCK (pad);
      break;
  }
}

static void
post_activate (GstPad * pad, GstActivateMode new_mode)
{
  switch (new_mode) {
    case GST_ACTIVATE_PUSH:
    case GST_ACTIVATE_PULL:
      /* nop */
      break;
    case GST_ACTIVATE_NONE:
      /* ensures that streaming stops */
      GST_PAD_STREAM_LOCK (pad);
      GST_DEBUG_OBJECT (pad, "stopped streaming");
      GST_OBJECT_LOCK (pad);
      clear_events (pad->priv->events);
      GST_OBJECT_UNLOCK (pad);
      GST_PAD_STREAM_UNLOCK (pad);
      break;
  }
}

/**
 * gst_pad_set_active:
 * @pad: the #GstPad to activate or deactivate.
 * @active: whether or not the pad should be active.
 *
 * Activates or deactivates the given pad.
 * Normally called from within core state change functions.
 *
 * If @active, makes sure the pad is active. If it is already active, either in
 * push or pull mode, just return. Otherwise dispatches to the pad's activate
 * function to perform the actual activation.
 *
 * If not @active, checks the pad's current mode and calls
 * gst_pad_activate_push() or gst_pad_activate_pull(), as appropriate, with a
 * FALSE argument.
 *
 * Returns: #TRUE if the operation was successful.
 *
 * MT safe.
 */
gboolean
gst_pad_set_active (GstPad * pad, gboolean active)
{
  GstActivateMode old;
  gboolean ret = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_OBJECT_LOCK (pad);
  old = GST_PAD_ACTIVATE_MODE (pad);
  GST_OBJECT_UNLOCK (pad);

  if (active) {
    switch (old) {
      case GST_ACTIVATE_PUSH:
        GST_DEBUG_OBJECT (pad, "activating pad from push");
        ret = TRUE;
        break;
      case GST_ACTIVATE_PULL:
        GST_DEBUG_OBJECT (pad, "activating pad from pull");
        ret = TRUE;
        break;
      case GST_ACTIVATE_NONE:
        GST_DEBUG_OBJECT (pad, "activating pad from none");
        ret = (GST_PAD_ACTIVATEFUNC (pad)) (pad);
        break;
      default:
        GST_DEBUG_OBJECT (pad, "unknown activation mode!");
        break;
    }
  } else {
    switch (old) {
      case GST_ACTIVATE_PUSH:
        GST_DEBUG_OBJECT (pad, "deactivating pad from push");
        ret = gst_pad_activate_push (pad, FALSE);
        break;
      case GST_ACTIVATE_PULL:
        GST_DEBUG_OBJECT (pad, "deactivating pad from pull");
        ret = gst_pad_activate_pull (pad, FALSE);
        break;
      case GST_ACTIVATE_NONE:
        GST_DEBUG_OBJECT (pad, "deactivating pad from none");
        ret = TRUE;
        break;
      default:
        GST_DEBUG_OBJECT (pad, "unknown activation mode!");
        break;
    }
  }

  if (!ret) {
    GST_OBJECT_LOCK (pad);
    if (!active) {
      g_critical ("Failed to deactivate pad %s:%s, very bad",
          GST_DEBUG_PAD_NAME (pad));
    } else {
      GST_WARNING_OBJECT (pad, "Failed to activate pad");
    }
    GST_OBJECT_UNLOCK (pad);
  } else {
    if (!active) {
      GST_OBJECT_LOCK (pad);
      GST_OBJECT_FLAG_UNSET (pad, GST_PAD_NEED_RECONFIGURE);
      GST_OBJECT_UNLOCK (pad);
    }
  }

  return ret;
}

/**
 * gst_pad_activate_pull:
 * @pad: the #GstPad to activate or deactivate.
 * @active: whether or not the pad should be active.
 *
 * Activates or deactivates the given pad in pull mode via dispatching to the
 * pad's activatepullfunc. For use from within pad activation functions only.
 * When called on sink pads, will first proxy the call to the peer pad, which
 * is expected to activate its internally linked pads from within its
 * activate_pull function.
 *
 * If you don't know what this is, you probably don't want to call it.
 *
 * Returns: TRUE if the operation was successful.
 *
 * MT safe.
 */
gboolean
gst_pad_activate_pull (GstPad * pad, gboolean active)
{
  GstActivateMode old, new;
  GstPad *peer;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_OBJECT_LOCK (pad);
  old = GST_PAD_ACTIVATE_MODE (pad);
  GST_OBJECT_UNLOCK (pad);

  if (active) {
    switch (old) {
      case GST_ACTIVATE_PULL:
        GST_DEBUG_OBJECT (pad, "activating pad from pull, was ok");
        goto was_ok;
      case GST_ACTIVATE_PUSH:
        GST_DEBUG_OBJECT (pad,
            "activating pad from push, deactivate push first");
        /* pad was activate in the wrong direction, deactivate it
         * and reactivate it in pull mode */
        if (G_UNLIKELY (!gst_pad_activate_push (pad, FALSE)))
          goto deactivate_failed;
        /* fallthrough, pad is deactivated now. */
      case GST_ACTIVATE_NONE:
        GST_DEBUG_OBJECT (pad, "activating pad from none");
        break;
    }
  } else {
    switch (old) {
      case GST_ACTIVATE_NONE:
        GST_DEBUG_OBJECT (pad, "deactivating pad from none, was ok");
        goto was_ok;
      case GST_ACTIVATE_PUSH:
        GST_DEBUG_OBJECT (pad, "deactivating pad from push, weird");
        /* pad was activated in the other direction, deactivate it
         * in push mode, this should not happen... */
        if (G_UNLIKELY (!gst_pad_activate_push (pad, FALSE)))
          goto deactivate_failed;
        /* everything is fine now */
        goto was_ok;
      case GST_ACTIVATE_PULL:
        GST_DEBUG_OBJECT (pad, "deactivating pad from pull");
        break;
    }
  }

  if (gst_pad_get_direction (pad) == GST_PAD_SINK) {
    if ((peer = gst_pad_get_peer (pad))) {
      GST_DEBUG_OBJECT (pad, "calling peer");
      if (G_UNLIKELY (!gst_pad_activate_pull (peer, active)))
        goto peer_failed;
      gst_object_unref (peer);
    } else {
      /* there is no peer, this is only fatal when we activate. When we
       * deactivate, we must assume the application has unlinked the peer and
       * will deactivate it eventually. */
      if (active)
        goto not_linked;
      else
        GST_DEBUG_OBJECT (pad, "deactivating unlinked pad");
    }
  } else {
    if (G_UNLIKELY (GST_PAD_GETRANGEFUNC (pad) == NULL))
      goto failure;             /* Can't activate pull on a src without a
                                   getrange function */
  }

  new = active ? GST_ACTIVATE_PULL : GST_ACTIVATE_NONE;
  pre_activate (pad, new);

  if (GST_PAD_ACTIVATEPULLFUNC (pad)) {
    if (G_UNLIKELY (!GST_PAD_ACTIVATEPULLFUNC (pad) (pad, active)))
      goto failure;
  } else {
    /* can happen for sinks of passthrough elements */
  }

  post_activate (pad, new);

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "%s in pull mode",
      active ? "activated" : "deactivated");

  return TRUE;

was_ok:
  {
    GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "already %s in pull mode",
        active ? "activated" : "deactivated");
    return TRUE;
  }
deactivate_failed:
  {
    GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad,
        "failed to %s in switch to pull from mode %d",
        (active ? "activate" : "deactivate"), old);
    return FALSE;
  }
peer_failed:
  {
    GST_OBJECT_LOCK (peer);
    GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad,
        "activate_pull on peer (%s:%s) failed", GST_DEBUG_PAD_NAME (peer));
    GST_OBJECT_UNLOCK (peer);
    gst_object_unref (peer);
    return FALSE;
  }
not_linked:
  {
    GST_CAT_INFO_OBJECT (GST_CAT_PADS, pad, "can't activate unlinked sink "
        "pad in pull mode");
    return FALSE;
  }
failure:
  {
    GST_OBJECT_LOCK (pad);
    GST_CAT_INFO_OBJECT (GST_CAT_PADS, pad, "failed to %s in pull mode",
        active ? "activate" : "deactivate");
    GST_PAD_SET_FLUSHING (pad);
    GST_PAD_ACTIVATE_MODE (pad) = old;
    GST_OBJECT_UNLOCK (pad);
    return FALSE;
  }
}

/**
 * gst_pad_activate_push:
 * @pad: the #GstPad to activate or deactivate.
 * @active: whether the pad should be active or not.
 *
 * Activates or deactivates the given pad in push mode via dispatching to the
 * pad's activatepushfunc. For use from within pad activation functions only.
 *
 * If you don't know what this is, you probably don't want to call it.
 *
 * Returns: %TRUE if the operation was successful.
 *
 * MT safe.
 */
gboolean
gst_pad_activate_push (GstPad * pad, gboolean active)
{
  GstActivateMode old, new;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "trying to set %s in push mode",
      active ? "activated" : "deactivated");

  GST_OBJECT_LOCK (pad);
  old = GST_PAD_ACTIVATE_MODE (pad);
  GST_OBJECT_UNLOCK (pad);

  if (active) {
    switch (old) {
      case GST_ACTIVATE_PUSH:
        GST_DEBUG_OBJECT (pad, "activating pad from push, was ok");
        goto was_ok;
      case GST_ACTIVATE_PULL:
        GST_DEBUG_OBJECT (pad,
            "activating pad from push, deactivating pull first");
        /* pad was activate in the wrong direction, deactivate it
         * an reactivate it in push mode */
        if (G_UNLIKELY (!gst_pad_activate_pull (pad, FALSE)))
          goto deactivate_failed;
        /* fallthrough, pad is deactivated now. */
      case GST_ACTIVATE_NONE:
        GST_DEBUG_OBJECT (pad, "activating pad from none");
        break;
    }
  } else {
    switch (old) {
      case GST_ACTIVATE_NONE:
        GST_DEBUG_OBJECT (pad, "deactivating pad from none, was ok");
        goto was_ok;
      case GST_ACTIVATE_PULL:
        GST_DEBUG_OBJECT (pad, "deactivating pad from pull, weird");
        /* pad was activated in the other direction, deactivate it
         * in pull mode, this should not happen... */
        if (G_UNLIKELY (!gst_pad_activate_pull (pad, FALSE)))
          goto deactivate_failed;
        /* everything is fine now */
        goto was_ok;
      case GST_ACTIVATE_PUSH:
        GST_DEBUG_OBJECT (pad, "deactivating pad from push");
        break;
    }
  }

  new = active ? GST_ACTIVATE_PUSH : GST_ACTIVATE_NONE;
  pre_activate (pad, new);

  if (GST_PAD_ACTIVATEPUSHFUNC (pad)) {
    if (G_UNLIKELY (!GST_PAD_ACTIVATEPUSHFUNC (pad) (pad, active))) {
      goto failure;
    }
  } else {
    /* quite ok, element relies on state change func to prepare itself */
  }

  post_activate (pad, new);

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "%s in push mode",
      active ? "activated" : "deactivated");
  return TRUE;

was_ok:
  {
    GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "already %s in push mode",
        active ? "activated" : "deactivated");
    return TRUE;
  }
deactivate_failed:
  {
    GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad,
        "failed to %s in switch to push from mode %d",
        (active ? "activate" : "deactivate"), old);
    return FALSE;
  }
failure:
  {
    GST_OBJECT_LOCK (pad);
    GST_CAT_INFO_OBJECT (GST_CAT_PADS, pad, "failed to %s in push mode",
        active ? "activate" : "deactivate");
    GST_PAD_SET_FLUSHING (pad);
    GST_PAD_ACTIVATE_MODE (pad) = old;
    GST_OBJECT_UNLOCK (pad);
    return FALSE;
  }
}

/**
 * gst_pad_is_active:
 * @pad: the #GstPad to query
 *
 * Query if a pad is active
 *
 * Returns: TRUE if the pad is active.
 *
 * MT safe.
 */
gboolean
gst_pad_is_active (GstPad * pad)
{
  gboolean result = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_OBJECT_LOCK (pad);
  result = GST_PAD_IS_ACTIVE (pad);
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/**
 * gst_pad_add_probe:
 * @pad: the #GstPad to add the probe to
 * @mask: the probe mask
 * @callback: #GstPadProbeCallback that will be called with notifications of
 *           the pad state
 * @user_data: (closure): user data passed to the callback
 * @destroy_data: #GDestroyNotify for user_data
 *
 * Be notified of different states of pads. The provided callback is called for
 * every state that matches @mask.
 *
 * <note>
 *  Pad probe handlers are only called for source pads in push mode
 *  and sink pads in pull mode.
 * </note>
 *
 * Returns: an id or 0 on error. The id can be used to remove the probe with
 * gst_pad_remove_probe().
 *
 * MT safe.
 */
gulong
gst_pad_add_probe (GstPad * pad, GstProbeType mask,
    GstPadProbeCallback callback, gpointer user_data,
    GDestroyNotify destroy_data)
{
  GHook *hook;
  gulong res;

  g_return_val_if_fail (GST_IS_PAD (pad), 0);
  g_return_val_if_fail (mask != 0, 0);

  GST_OBJECT_LOCK (pad);
  /* make a new probe */
  hook = g_hook_alloc (&pad->probes);

  GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "adding probe for mask 0x%08x",
      mask);

  /* when no contraints are given for the types, assume all types are
   * acceptable */
  if ((mask & GST_PROBE_TYPE_DATA) == 0)
    mask |= GST_PROBE_TYPE_DATA;
  if ((mask & GST_PROBE_TYPE_SCHEDULING) == 0)
    mask |= GST_PROBE_TYPE_SCHEDULING;

  /* store our flags and other fields */
  hook->flags |= (mask << G_HOOK_FLAG_USER_SHIFT);
  hook->func = callback;
  hook->data = user_data;
  hook->destroy = destroy_data;
  PROBE_COOKIE (hook) = 0;

  /* incremenent cookie so that the new hook get's called */
  pad->priv->probe_cookie++;

  /* add the probe */
  g_hook_prepend (&pad->probes, hook);
  pad->num_probes++;

  /* get the id of the hook, we return this and it can be used to remove the
   * probe later */
  res = hook->hook_id;

  GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "got probe id %lu", res);

  if (mask & GST_PROBE_TYPE_BLOCKING) {
    /* we have a block probe */
    pad->num_blocked++;
    GST_OBJECT_FLAG_SET (pad, GST_PAD_BLOCKED);
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "added blocking probe, "
        "now %d blocking probes", pad->num_blocked);
  }

  /* call the callback if we need to be called for idle callbacks */
  if ((mask & GST_PROBE_TYPE_IDLE) && (callback != NULL)) {
    if (pad->priv->using > 0) {
      /* the pad is in use, we can't signal the idle callback yet. Since we set the
       * flag above, the last thread to leave the push will do the callback. New
       * threads going into the push will block. */
      GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
          "pad is in use, delay idle callback");
      GST_OBJECT_UNLOCK (pad);
    } else {
      /* the pad is idle now, we can signal the idle callback now */
      GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
          "pad is idle, trigger idle callback");
      GST_OBJECT_UNLOCK (pad);

      callback (pad, GST_PROBE_TYPE_IDLE, NULL, user_data);
    }
  } else {
    GST_OBJECT_UNLOCK (pad);
  }
  return res;
}

static void
cleanup_hook (GstPad * pad, GHook * hook)
{
  GstProbeType type;

  type = (hook->flags) >> G_HOOK_FLAG_USER_SHIFT;

  if (type & GST_PROBE_TYPE_BLOCKING) {
    /* unblock when we remove the last blocking probe */
    pad->num_blocked--;
    GST_DEBUG_OBJECT (pad, "remove blocking probe, now %d left",
        pad->num_blocked);
    if (pad->num_blocked == 0) {
      GST_DEBUG_OBJECT (pad, "last blocking probe removed, unblocking");
      GST_OBJECT_FLAG_UNSET (pad, GST_PAD_BLOCKED);
      GST_PAD_BLOCK_BROADCAST (pad);
    }
  }
  g_hook_destroy_link (&pad->probes, hook);
  pad->num_probes--;
}

/**
 * gst_pad_remove_probe:
 * @pad: the #GstPad with the probe
 * @id: the probe id to remove
 *
 * Remove the probe with @id from @pad.
 *
 * MT safe.
 */
void
gst_pad_remove_probe (GstPad * pad, gulong id)
{
  GHook *hook;

  g_return_if_fail (GST_IS_PAD (pad));

  GST_OBJECT_LOCK (pad);

  hook = g_hook_get (&pad->probes, id);
  if (hook == NULL)
    goto not_found;

  GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "removing hook %ld",
      hook->hook_id);
  cleanup_hook (pad, hook);
  GST_OBJECT_UNLOCK (pad);

  return;

not_found:
  {
    GST_OBJECT_UNLOCK (pad);
    g_warning ("%s: pad `%p' has no probe with id `%lu'", G_STRLOC, pad, id);
    return;
  }
}

/**
 * gst_pad_is_blocked:
 * @pad: the #GstPad to query
 *
 * Checks if the pad is blocked or not. This function returns the
 * last requested state of the pad. It is not certain that the pad
 * is actually blocking at this point (see gst_pad_is_blocking()).
 *
 * Returns: TRUE if the pad is blocked.
 *
 * MT safe.
 */
gboolean
gst_pad_is_blocked (GstPad * pad)
{
  gboolean result = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), result);

  GST_OBJECT_LOCK (pad);
  result = GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_BLOCKED);
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/**
 * gst_pad_is_blocking:
 * @pad: the #GstPad to query
 *
 * Checks if the pad is blocking or not. This is a guaranteed state
 * of whether the pad is actually blocking on a #GstBuffer or a #GstEvent.
 *
 * Returns: TRUE if the pad is blocking.
 *
 * MT safe.
 *
 * Since: 0.10.11
 */
gboolean
gst_pad_is_blocking (GstPad * pad)
{
  gboolean result = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), result);

  GST_OBJECT_LOCK (pad);
  /* the blocking flag is only valid if the pad is not flushing */
  result = GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_BLOCKING) &&
      !GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLUSHING);
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/**
 * gst_pad_check_reconfigure:
 * @pad: the #GstPad to check
 *
 * Check and clear the #GST_PAD_NEED_RECONFIGURE flag on @pad and return %TRUE
 * if the flag was set.
 *
 * Returns: %TRUE is the GST_PAD_NEED_RECONFIGURE flag was set on @pad.
 */
gboolean
gst_pad_check_reconfigure (GstPad * pad)
{
  gboolean reconfigure;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_OBJECT_LOCK (pad);
  reconfigure = GST_PAD_NEEDS_RECONFIGURE (pad);
  GST_OBJECT_FLAG_UNSET (pad, GST_PAD_NEED_RECONFIGURE);
  GST_OBJECT_UNLOCK (pad);

  return reconfigure;
}

/**
 * gst_pad_mark_reconfigure:
 * @pad: the #GstPad to mark
 *
 * Mark a pad for needing reconfiguration. The next call to
 * gst_pad_check_reconfigure() will return %TRUE after this call.
 */
void
gst_pad_mark_reconfigure (GstPad * pad)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_OBJECT_LOCK (pad);
  GST_OBJECT_FLAG_SET (pad, GST_PAD_NEED_RECONFIGURE);
  GST_OBJECT_UNLOCK (pad);
}

/**
 * gst_pad_set_activate_function:
 * @pad: a #GstPad.
 * @activate: the #GstPadActivateFunction to set.
 *
 * Sets the given activate function for @pad. The activate function will
 * dispatch to gst_pad_activate_push() or gst_pad_activate_pull() to perform
 * the actual activation. Only makes sense to set on sink pads.
 *
 * Call this function if your sink pad can start a pull-based task.
 */
void
gst_pad_set_activate_function (GstPad * pad, GstPadActivateFunction activate)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_ACTIVATEFUNC (pad) = activate;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "activatefunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (activate));
}

/**
 * gst_pad_set_activatepull_function:
 * @pad: a #GstPad.
 * @activatepull: the #GstPadActivateModeFunction to set.
 *
 * Sets the given activate_pull function for the pad. An activate_pull function
 * prepares the element and any upstream connections for pulling. See XXX
 * part-activation.txt for details.
 */
void
gst_pad_set_activatepull_function (GstPad * pad,
    GstPadActivateModeFunction activatepull)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_ACTIVATEPULLFUNC (pad) = activatepull;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "activatepullfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (activatepull));
}

/**
 * gst_pad_set_activatepush_function:
 * @pad: a #GstPad.
 * @activatepush: the #GstPadActivateModeFunction to set.
 *
 * Sets the given activate_push function for the pad. An activate_push function
 * prepares the element for pushing. See XXX part-activation.txt for details.
 */
void
gst_pad_set_activatepush_function (GstPad * pad,
    GstPadActivateModeFunction activatepush)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_ACTIVATEPUSHFUNC (pad) = activatepush;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "activatepushfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (activatepush));
}

/**
 * gst_pad_set_chain_function:
 * @pad: a sink #GstPad.
 * @chain: the #GstPadChainFunction to set.
 *
 * Sets the given chain function for the pad. The chain function is called to
 * process a #GstBuffer input buffer. see #GstPadChainFunction for more details.
 */
void
gst_pad_set_chain_function (GstPad * pad, GstPadChainFunction chain)
{
  g_return_if_fail (GST_IS_PAD (pad));
  g_return_if_fail (GST_PAD_IS_SINK (pad));

  GST_PAD_CHAINFUNC (pad) = chain;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "chainfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (chain));
}

/**
 * gst_pad_set_chain_list_function:
 * @pad: a sink #GstPad.
 * @chainlist: the #GstPadChainListFunction to set.
 *
 * Sets the given chain list function for the pad. The chainlist function is
 * called to process a #GstBufferList input buffer list. See
 * #GstPadChainListFunction for more details.
 *
 * Since: 0.10.24
 */
void
gst_pad_set_chain_list_function (GstPad * pad,
    GstPadChainListFunction chainlist)
{
  g_return_if_fail (GST_IS_PAD (pad));
  g_return_if_fail (GST_PAD_IS_SINK (pad));

  GST_PAD_CHAINLISTFUNC (pad) = chainlist;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "chainlistfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (chainlist));
}

/**
 * gst_pad_set_getrange_function:
 * @pad: a source #GstPad.
 * @get: the #GstPadGetRangeFunction to set.
 *
 * Sets the given getrange function for the pad. The getrange function is
 * called to produce a new #GstBuffer to start the processing pipeline. see
 * #GstPadGetRangeFunction for a description of the getrange function.
 */
void
gst_pad_set_getrange_function (GstPad * pad, GstPadGetRangeFunction get)
{
  g_return_if_fail (GST_IS_PAD (pad));
  g_return_if_fail (GST_PAD_IS_SRC (pad));

  GST_PAD_GETRANGEFUNC (pad) = get;

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "getrangefunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (get));
}

/**
 * gst_pad_set_event_function:
 * @pad: a #GstPad of either direction.
 * @event: the #GstPadEventFunction to set.
 *
 * Sets the given event handler for the pad.
 */
void
gst_pad_set_event_function (GstPad * pad, GstPadEventFunction event)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_EVENTFUNC (pad) = event;

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "eventfunc for set to %s",
      GST_DEBUG_FUNCPTR_NAME (event));
}

/**
 * gst_pad_set_query_function:
 * @pad: a #GstPad of either direction.
 * @query: the #GstPadQueryFunction to set.
 *
 * Set the given query function for the pad.
 */
void
gst_pad_set_query_function (GstPad * pad, GstPadQueryFunction query)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_QUERYFUNC (pad) = query;

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "queryfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (query));
}

/**
 * gst_pad_set_query_type_function:
 * @pad: a #GstPad of either direction.
 * @type_func: the #GstPadQueryTypeFunction to set.
 *
 * Set the given query type function for the pad.
 */
void
gst_pad_set_query_type_function (GstPad * pad,
    GstPadQueryTypeFunction type_func)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_QUERYTYPEFUNC (pad) = type_func;

  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "querytypefunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (type_func));
}

/**
 * gst_pad_get_query_types:
 * @pad: a #GstPad.
 *
 * Get an array of supported queries that can be performed
 * on this pad.
 *
 * Returns: (transfer none) (array zero-terminated=1): a zero-terminated array
 *     of #GstQueryType.
 */
const GstQueryType *
gst_pad_get_query_types (GstPad * pad)
{
  GstPadQueryTypeFunction func;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  if (G_UNLIKELY ((func = GST_PAD_QUERYTYPEFUNC (pad)) == NULL))
    goto no_func;

  return func (pad);

no_func:
  {
    return NULL;
  }
}

static gboolean
gst_pad_get_query_types_dispatcher (GstPad * pad, const GstQueryType ** data)
{
  GstPad *peer;

  if ((peer = gst_pad_get_peer (pad))) {
    *data = gst_pad_get_query_types (peer);
    gst_object_unref (peer);
  }
  return TRUE;
}

/**
 * gst_pad_get_query_types_default:
 * @pad: a #GstPad.
 *
 * Invoke the default query types function on the pad. This function will get
 * the supported query type from the peer of an internally linked pad of @pad.
 *
 * Returns: (transfer none) (array zero-terminated=1): a zero-terminated array
 *     of #GstQueryType, or NULL if none of the internally-linked pads has a
 *     query types function.
 */
const GstQueryType *
gst_pad_get_query_types_default (GstPad * pad)
{
  GstQueryType *result = NULL;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  gst_pad_forward (pad, (GstPadForwardFunction)
      gst_pad_get_query_types_dispatcher, &result);

  return result;
}

/**
 * gst_pad_set_iterate_internal_links_function:
 * @pad: a #GstPad of either direction.
 * @iterintlink: the #GstPadIterIntLinkFunction to set.
 *
 * Sets the given internal link iterator function for the pad.
 *
 * Since: 0.10.21
 */
void
gst_pad_set_iterate_internal_links_function (GstPad * pad,
    GstPadIterIntLinkFunction iterintlink)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_ITERINTLINKFUNC (pad) = iterintlink;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "internal link iterator set to %s",
      GST_DEBUG_FUNCPTR_NAME (iterintlink));
}

/**
 * gst_pad_set_link_function:
 * @pad: a #GstPad.
 * @link: the #GstPadLinkFunction to set.
 *
 * Sets the given link function for the pad. It will be called when
 * the pad is linked with another pad.
 *
 * The return value #GST_PAD_LINK_OK should be used when the connection can be
 * made.
 *
 * The return value #GST_PAD_LINK_REFUSED should be used when the connection
 * cannot be made for some reason.
 *
 * If @link is installed on a source pad, it should call the #GstPadLinkFunction
 * of the peer sink pad, if present.
 */
void
gst_pad_set_link_function (GstPad * pad, GstPadLinkFunction link)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_LINKFUNC (pad) = link;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "linkfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (link));
}

/**
 * gst_pad_set_unlink_function:
 * @pad: a #GstPad.
 * @unlink: the #GstPadUnlinkFunction to set.
 *
 * Sets the given unlink function for the pad. It will be called
 * when the pad is unlinked.
 */
void
gst_pad_set_unlink_function (GstPad * pad, GstPadUnlinkFunction unlink)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_UNLINKFUNC (pad) = unlink;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "unlinkfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (unlink));
}

/**
 * gst_pad_set_getcaps_function:
 * @pad: a #GstPad.
 * @getcaps: the #GstPadGetCapsFunction to set.
 *
 * Sets the given getcaps function for the pad. @getcaps should return the
 * allowable caps for a pad in the context of the element's state, its link to
 * other elements, and the devices or files it has opened. These caps must be a
 * subset of the pad template caps. In the NULL state with no links, @getcaps
 * should ideally return the same caps as the pad template. In rare
 * circumstances, an object property can affect the caps returned by @getcaps,
 * but this is discouraged.
 *
 * You do not need to call this function if @pad's allowed caps are always the
 * same as the pad template caps. This can only be true if the padtemplate
 * has fixed simple caps.
 *
 * For most filters, the caps returned by @getcaps is directly affected by the
 * allowed caps on other pads. For demuxers and decoders, the caps returned by
 * the srcpad's getcaps function is directly related to the stream data. Again,
 * @getcaps should return the most specific caps it reasonably can, since this
 * helps with autoplugging.
 *
 * Note that the return value from @getcaps is owned by the caller, so the
 * caller should unref the caps after usage.
 */
void
gst_pad_set_getcaps_function (GstPad * pad, GstPadGetCapsFunction getcaps)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_GETCAPSFUNC (pad) = getcaps;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "getcapsfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (getcaps));
}

/**
 * gst_pad_set_acceptcaps_function:
 * @pad: a #GstPad.
 * @acceptcaps: the #GstPadAcceptCapsFunction to set.
 *
 * Sets the given acceptcaps function for the pad.  The acceptcaps function
 * will be called to check if the pad can accept the given caps. Setting the
 * acceptcaps function to NULL restores the default behaviour of allowing
 * any caps that matches the caps from gst_pad_get_caps().
 */
void
gst_pad_set_acceptcaps_function (GstPad * pad,
    GstPadAcceptCapsFunction acceptcaps)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_ACCEPTCAPSFUNC (pad) = acceptcaps;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "acceptcapsfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (acceptcaps));
}

/**
 * gst_pad_set_fixatecaps_function:
 * @pad: a #GstPad.
 * @fixatecaps: the #GstPadFixateCapsFunction to set.
 *
 * Sets the given fixatecaps function for the pad.  The fixatecaps function
 * will be called whenever the default values for a GstCaps needs to be
 * filled in.
 */
void
gst_pad_set_fixatecaps_function (GstPad * pad,
    GstPadFixateCapsFunction fixatecaps)
{
  g_return_if_fail (GST_IS_PAD (pad));

  GST_PAD_FIXATECAPSFUNC (pad) = fixatecaps;
  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "fixatecapsfunc set to %s",
      GST_DEBUG_FUNCPTR_NAME (fixatecaps));
}

/**
 * gst_pad_unlink:
 * @srcpad: the source #GstPad to unlink.
 * @sinkpad: the sink #GstPad to unlink.
 *
 * Unlinks the source pad from the sink pad. Will emit the #GstPad::unlinked
 * signal on both pads.
 *
 * Returns: TRUE if the pads were unlinked. This function returns FALSE if
 * the pads were not linked together.
 *
 * MT safe.
 */
gboolean
gst_pad_unlink (GstPad * srcpad, GstPad * sinkpad)
{
  gboolean result = FALSE;
  GstElement *parent = NULL;
  gint i;

  g_return_val_if_fail (GST_IS_PAD (srcpad), FALSE);
  g_return_val_if_fail (GST_PAD_IS_SRC (srcpad), FALSE);
  g_return_val_if_fail (GST_IS_PAD (sinkpad), FALSE);
  g_return_val_if_fail (GST_PAD_IS_SINK (sinkpad), FALSE);

  GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "unlinking %s:%s(%p) and %s:%s(%p)",
      GST_DEBUG_PAD_NAME (srcpad), srcpad,
      GST_DEBUG_PAD_NAME (sinkpad), sinkpad);

  /* We need to notify the parent before taking any pad locks as the bin in
   * question might be waiting for a lock on the pad while holding its lock
   * that our message will try to take. */
  if ((parent = GST_ELEMENT_CAST (gst_pad_get_parent (srcpad)))) {
    if (GST_IS_ELEMENT (parent)) {
      gst_element_post_message (parent,
          gst_message_new_structure_change (GST_OBJECT_CAST (sinkpad),
              GST_STRUCTURE_CHANGE_TYPE_PAD_UNLINK, parent, TRUE));
    } else {
      gst_object_unref (parent);
      parent = NULL;
    }
  }

  GST_OBJECT_LOCK (srcpad);
  GST_OBJECT_LOCK (sinkpad);

  if (G_UNLIKELY (GST_PAD_PEER (srcpad) != sinkpad))
    goto not_linked_together;

  if (GST_PAD_UNLINKFUNC (srcpad)) {
    GST_PAD_UNLINKFUNC (srcpad) (srcpad);
  }
  if (GST_PAD_UNLINKFUNC (sinkpad)) {
    GST_PAD_UNLINKFUNC (sinkpad) (sinkpad);
  }

  /* first clear peers */
  GST_PAD_PEER (srcpad) = NULL;
  GST_PAD_PEER (sinkpad) = NULL;

  /* clear pending caps if any */
  for (i = 0; i < GST_EVENT_MAX_STICKY; i++)
    gst_event_replace (&sinkpad->priv->events[i].pending, NULL);

  GST_OBJECT_UNLOCK (sinkpad);
  GST_OBJECT_UNLOCK (srcpad);

  /* fire off a signal to each of the pads telling them
   * that they've been unlinked */
  g_signal_emit (srcpad, gst_pad_signals[PAD_UNLINKED], 0, sinkpad);
  g_signal_emit (sinkpad, gst_pad_signals[PAD_UNLINKED], 0, srcpad);

  GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "unlinked %s:%s and %s:%s",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  result = TRUE;

done:
  if (parent != NULL) {
    gst_element_post_message (parent,
        gst_message_new_structure_change (GST_OBJECT_CAST (sinkpad),
            GST_STRUCTURE_CHANGE_TYPE_PAD_UNLINK, parent, FALSE));
    gst_object_unref (parent);
  }
  return result;

  /* ERRORS */
not_linked_together:
  {
    /* we do not emit a warning in this case because unlinking cannot
     * be made MT safe.*/
    GST_OBJECT_UNLOCK (sinkpad);
    GST_OBJECT_UNLOCK (srcpad);
    goto done;
  }
}

/**
 * gst_pad_is_linked:
 * @pad: pad to check
 *
 * Checks if a @pad is linked to another pad or not.
 *
 * Returns: TRUE if the pad is linked, FALSE otherwise.
 *
 * MT safe.
 */
gboolean
gst_pad_is_linked (GstPad * pad)
{
  gboolean result;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_OBJECT_LOCK (pad);
  result = (GST_PAD_PEER (pad) != NULL);
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/* get the caps from both pads and see if the intersection
 * is not empty.
 *
 * This function should be called with the pad LOCK on both
 * pads
 */
static gboolean
gst_pad_link_check_compatible_unlocked (GstPad * src, GstPad * sink,
    GstPadLinkCheck flags)
{
  GstCaps *srccaps = NULL;
  GstCaps *sinkcaps = NULL;
  gboolean compatible = FALSE;

  if (!(flags & (GST_PAD_LINK_CHECK_CAPS | GST_PAD_LINK_CHECK_TEMPLATE_CAPS)))
    return TRUE;

  /* Doing the expensive caps checking takes priority over only checking the template caps */
  if (flags & GST_PAD_LINK_CHECK_CAPS) {
    srccaps = gst_pad_get_caps_unlocked (src, NULL);
    sinkcaps = gst_pad_get_caps_unlocked (sink, NULL);
  } else {
    /* If one of the two pads doesn't have a template, consider the intersection
     * as valid.*/
    if (G_UNLIKELY ((GST_PAD_PAD_TEMPLATE (src) == NULL)
            || (GST_PAD_PAD_TEMPLATE (sink) == NULL))) {
      compatible = TRUE;
      goto done;
    }
    srccaps = gst_caps_ref (GST_PAD_TEMPLATE_CAPS (GST_PAD_PAD_TEMPLATE (src)));
    sinkcaps =
        gst_caps_ref (GST_PAD_TEMPLATE_CAPS (GST_PAD_PAD_TEMPLATE (sink)));
  }

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, src, "src caps %" GST_PTR_FORMAT,
      srccaps);
  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, sink, "sink caps %" GST_PTR_FORMAT,
      sinkcaps);

  /* if we have caps on both pads we can check the intersection. If one
   * of the caps is NULL, we return TRUE. */
  if (G_UNLIKELY (srccaps == NULL || sinkcaps == NULL)) {
    if (srccaps)
      gst_caps_unref (srccaps);
    if (sinkcaps)
      gst_caps_unref (sinkcaps);
    goto done;
  }

  compatible = gst_caps_can_intersect (srccaps, sinkcaps);
  gst_caps_unref (srccaps);
  gst_caps_unref (sinkcaps);

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

  return compatible;
}

/* check if the grandparents of both pads are the same.
 * This check is required so that we don't try to link
 * pads from elements in different bins without ghostpads.
 *
 * The LOCK should be held on both pads
 */
static gboolean
gst_pad_link_check_hierarchy (GstPad * src, GstPad * sink)
{
  GstObject *psrc, *psink;

  psrc = GST_OBJECT_PARENT (src);
  psink = GST_OBJECT_PARENT (sink);

  /* if one of the pads has no parent, we allow the link */
  if (G_UNLIKELY (psrc == NULL || psink == NULL))
    goto no_parent;

  /* only care about parents that are elements */
  if (G_UNLIKELY (!GST_IS_ELEMENT (psrc) || !GST_IS_ELEMENT (psink)))
    goto no_element_parent;

  /* if the parents are the same, we have a loop */
  if (G_UNLIKELY (psrc == psink))
    goto same_parents;

  /* if they both have a parent, we check the grandparents. We can not lock
   * the parent because we hold on the child (pad) and the locking order is
   * parent >> child. */
  psrc = GST_OBJECT_PARENT (psrc);
  psink = GST_OBJECT_PARENT (psink);

  /* if they have grandparents but they are not the same */
  if (G_UNLIKELY (psrc != psink))
    goto wrong_grandparents;

  return TRUE;

  /* ERRORS */
no_parent:
  {
    GST_CAT_DEBUG (GST_CAT_CAPS,
        "one of the pads has no parent %" GST_PTR_FORMAT " and %"
        GST_PTR_FORMAT, psrc, psink);
    return TRUE;
  }
no_element_parent:
  {
    GST_CAT_DEBUG (GST_CAT_CAPS,
        "one of the pads has no element parent %" GST_PTR_FORMAT " and %"
        GST_PTR_FORMAT, psrc, psink);
    return TRUE;
  }
same_parents:
  {
    GST_CAT_DEBUG (GST_CAT_CAPS, "pads have same parent %" GST_PTR_FORMAT,
        psrc);
    return FALSE;
  }
wrong_grandparents:
  {
    GST_CAT_DEBUG (GST_CAT_CAPS,
        "pads have different grandparents %" GST_PTR_FORMAT " and %"
        GST_PTR_FORMAT, psrc, psink);
    return FALSE;
  }
}

/* FIXME leftover from an attempt at refactoring... */
/* call with the two pads unlocked, when this function returns GST_PAD_LINK_OK,
 * the two pads will be locked in the srcpad, sinkpad order. */
static GstPadLinkReturn
gst_pad_link_prepare (GstPad * srcpad, GstPad * sinkpad, GstPadLinkCheck flags)
{
  GST_CAT_INFO (GST_CAT_PADS, "trying to link %s:%s and %s:%s",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  GST_OBJECT_LOCK (srcpad);

  if (G_UNLIKELY (GST_PAD_PEER (srcpad) != NULL))
    goto src_was_linked;

  GST_OBJECT_LOCK (sinkpad);

  if (G_UNLIKELY (GST_PAD_PEER (sinkpad) != NULL))
    goto sink_was_linked;

  /* check hierarchy, pads can only be linked if the grandparents
   * are the same. */
  if ((flags & GST_PAD_LINK_CHECK_HIERARCHY)
      && !gst_pad_link_check_hierarchy (srcpad, sinkpad))
    goto wrong_hierarchy;

  /* check pad caps for non-empty intersection */
  if (!gst_pad_link_check_compatible_unlocked (srcpad, sinkpad, flags))
    goto no_format;

  /* FIXME check pad scheduling for non-empty intersection */

  return GST_PAD_LINK_OK;

src_was_linked:
  {
    GST_CAT_INFO (GST_CAT_PADS, "src %s:%s was already linked to %s:%s",
        GST_DEBUG_PAD_NAME (srcpad),
        GST_DEBUG_PAD_NAME (GST_PAD_PEER (srcpad)));
    /* we do not emit a warning in this case because unlinking cannot
     * be made MT safe.*/
    GST_OBJECT_UNLOCK (srcpad);
    return GST_PAD_LINK_WAS_LINKED;
  }
sink_was_linked:
  {
    GST_CAT_INFO (GST_CAT_PADS, "sink %s:%s was already linked to %s:%s",
        GST_DEBUG_PAD_NAME (sinkpad),
        GST_DEBUG_PAD_NAME (GST_PAD_PEER (sinkpad)));
    /* we do not emit a warning in this case because unlinking cannot
     * be made MT safe.*/
    GST_OBJECT_UNLOCK (sinkpad);
    GST_OBJECT_UNLOCK (srcpad);
    return GST_PAD_LINK_WAS_LINKED;
  }
wrong_hierarchy:
  {
    GST_CAT_INFO (GST_CAT_PADS, "pads have wrong hierarchy");
    GST_OBJECT_UNLOCK (sinkpad);
    GST_OBJECT_UNLOCK (srcpad);
    return GST_PAD_LINK_WRONG_HIERARCHY;
  }
no_format:
  {
    GST_CAT_INFO (GST_CAT_PADS, "caps are incompatible");
    GST_OBJECT_UNLOCK (sinkpad);
    GST_OBJECT_UNLOCK (srcpad);
    return GST_PAD_LINK_NOFORMAT;
  }
}

/**
 * gst_pad_can_link:
 * @srcpad: the source #GstPad.
 * @sinkpad: the sink #GstPad.
 *
 * Checks if the source pad and the sink pad are compatible so they can be
 * linked.
 *
 * Returns: TRUE if the pads can be linked.
 */
gboolean
gst_pad_can_link (GstPad * srcpad, GstPad * sinkpad)
{
  GstPadLinkReturn result;

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

  GST_CAT_INFO (GST_CAT_PADS, "check if %s:%s can link with %s:%s",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  /* gst_pad_link_prepare does everything for us, we only release the locks
   * on the pads that it gets us. If this function returns !OK the locks are not
   * taken anymore. */
  result = gst_pad_link_prepare (srcpad, sinkpad, GST_PAD_LINK_CHECK_DEFAULT);
  if (result != GST_PAD_LINK_OK)
    goto done;

  GST_OBJECT_UNLOCK (srcpad);
  GST_OBJECT_UNLOCK (sinkpad);

done:
  return result == GST_PAD_LINK_OK;
}

/**
 * gst_pad_link_full:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 * @flags: the checks to validate when linking
 *
 * Links the source pad and the sink pad.
 *
 * This variant of #gst_pad_link provides a more granular control on the
 * checks being done when linking. While providing some considerable speedups
 * the caller of this method must be aware that wrong usage of those flags
 * can cause severe issues. Refer to the documentation of #GstPadLinkCheck
 * for more information.
 *
 * MT Safe.
 *
 * Returns: A result code indicating if the connection worked or
 *          what went wrong.
 *
 * Since: 0.10.30
 */
GstPadLinkReturn
gst_pad_link_full (GstPad * srcpad, GstPad * sinkpad, GstPadLinkCheck flags)
{
  GstPadLinkReturn result;
  GstElement *parent;
  GstPadLinkFunction srcfunc, sinkfunc;

  g_return_val_if_fail (GST_IS_PAD (srcpad), GST_PAD_LINK_REFUSED);
  g_return_val_if_fail (GST_PAD_IS_SRC (srcpad), GST_PAD_LINK_WRONG_DIRECTION);
  g_return_val_if_fail (GST_IS_PAD (sinkpad), GST_PAD_LINK_REFUSED);
  g_return_val_if_fail (GST_PAD_IS_SINK (sinkpad),
      GST_PAD_LINK_WRONG_DIRECTION);

  /* Notify the parent early. See gst_pad_unlink for details. */
  if (G_LIKELY ((parent = GST_ELEMENT_CAST (gst_pad_get_parent (srcpad))))) {
    if (G_LIKELY (GST_IS_ELEMENT (parent))) {
      gst_element_post_message (parent,
          gst_message_new_structure_change (GST_OBJECT_CAST (sinkpad),
              GST_STRUCTURE_CHANGE_TYPE_PAD_LINK, parent, TRUE));
    } else {
      gst_object_unref (parent);
      parent = NULL;
    }
  }

  /* prepare will also lock the two pads */
  result = gst_pad_link_prepare (srcpad, sinkpad, flags);

  if (G_UNLIKELY (result != GST_PAD_LINK_OK))
    goto done;

  /* must set peers before calling the link function */
  GST_PAD_PEER (srcpad) = sinkpad;
  GST_PAD_PEER (sinkpad) = srcpad;

  /* make sure we update events */
  prepare_event_update (srcpad, sinkpad);

  /* get the link functions */
  srcfunc = GST_PAD_LINKFUNC (srcpad);
  sinkfunc = GST_PAD_LINKFUNC (sinkpad);

  if (G_UNLIKELY (srcfunc || sinkfunc)) {
    /* custom link functions, execute them */
    GST_OBJECT_UNLOCK (sinkpad);
    GST_OBJECT_UNLOCK (srcpad);

    if (srcfunc) {
      /* this one will call the peer link function */
      result = srcfunc (srcpad, sinkpad);
    } else if (sinkfunc) {
      /* if no source link function, we need to call the sink link
       * function ourselves. */
      result = sinkfunc (sinkpad, srcpad);
    }

    GST_OBJECT_LOCK (srcpad);
    GST_OBJECT_LOCK (sinkpad);

    /* we released the lock, check if the same pads are linked still */
    if (GST_PAD_PEER (srcpad) != sinkpad || GST_PAD_PEER (sinkpad) != srcpad)
      goto concurrent_link;

    if (G_UNLIKELY (result != GST_PAD_LINK_OK))
      goto link_failed;
  }
  GST_OBJECT_UNLOCK (sinkpad);
  GST_OBJECT_UNLOCK (srcpad);

  /* fire off a signal to each of the pads telling them
   * that they've been linked */
  g_signal_emit (srcpad, gst_pad_signals[PAD_LINKED], 0, sinkpad);
  g_signal_emit (sinkpad, gst_pad_signals[PAD_LINKED], 0, srcpad);

  GST_CAT_INFO (GST_CAT_PADS, "linked %s:%s and %s:%s, successful",
      GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  gst_pad_send_event (srcpad, gst_event_new_reconfigure ());

done:
  if (G_LIKELY (parent)) {
    gst_element_post_message (parent,
        gst_message_new_structure_change (GST_OBJECT_CAST (sinkpad),
            GST_STRUCTURE_CHANGE_TYPE_PAD_LINK, parent, FALSE));
    gst_object_unref (parent);
  }

  return result;

  /* ERRORS */
concurrent_link:
  {
    GST_CAT_INFO (GST_CAT_PADS, "concurrent link between %s:%s and %s:%s",
        GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));
    GST_OBJECT_UNLOCK (sinkpad);
    GST_OBJECT_UNLOCK (srcpad);

    /* The other link operation succeeded first */
    result = GST_PAD_LINK_WAS_LINKED;
    goto done;
  }
link_failed:
  {
    GST_CAT_INFO (GST_CAT_PADS, "link between %s:%s and %s:%s failed",
        GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

    GST_PAD_PEER (srcpad) = NULL;
    GST_PAD_PEER (sinkpad) = NULL;

    GST_OBJECT_UNLOCK (sinkpad);
    GST_OBJECT_UNLOCK (srcpad);

    goto done;
  }
}

/**
 * gst_pad_link:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 *
 * Links the source pad and the sink pad.
 *
 * Returns: A result code indicating if the connection worked or
 *          what went wrong.
 *
 * MT Safe.
 */
GstPadLinkReturn
gst_pad_link (GstPad * srcpad, GstPad * sinkpad)
{
  return gst_pad_link_full (srcpad, sinkpad, GST_PAD_LINK_CHECK_DEFAULT);
}

static void
gst_pad_set_pad_template (GstPad * pad, GstPadTemplate * templ)
{
  GstPadTemplate **template_p;

  /* this function would need checks if it weren't static */

  GST_OBJECT_LOCK (pad);
  template_p = &pad->padtemplate;
  gst_object_replace ((GstObject **) template_p, (GstObject *) templ);
  GST_OBJECT_UNLOCK (pad);

  if (templ)
    gst_pad_template_pad_created (templ, pad);
}

/**
 * gst_pad_get_pad_template:
 * @pad: a #GstPad.
 *
 * Gets the template for @pad.
 *
 * Returns: (transfer full): the #GstPadTemplate from which this pad was
 *     instantiated, or %NULL if this pad has no template. Unref after
 *     usage.
 */
GstPadTemplate *
gst_pad_get_pad_template (GstPad * pad)
{
  GstPadTemplate *templ;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  templ = GST_PAD_PAD_TEMPLATE (pad);

  return (templ ? gst_object_ref (templ) : NULL);
}

static GstCaps *
caps_with_getcaps (GstPad * pad, GstCaps * filter)
{
  GstCaps *result;

  if (GST_PAD_GETCAPSFUNC (pad) == NULL)
    return NULL;

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
      "dispatching to pad getcaps function with "
      "filter %" GST_PTR_FORMAT, filter);

  GST_OBJECT_FLAG_SET (pad, GST_PAD_IN_GETCAPS);
  GST_OBJECT_UNLOCK (pad);
  result = GST_PAD_GETCAPSFUNC (pad) (pad, filter);
  GST_OBJECT_LOCK (pad);
  GST_OBJECT_FLAG_UNSET (pad, GST_PAD_IN_GETCAPS);

  if (G_UNLIKELY (result == NULL))
    goto null_caps;

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
      "pad getcaps returned %" GST_PTR_FORMAT, result);

#ifndef G_DISABLE_ASSERT
  /* check that the returned caps are a real subset of the template caps */
  if (GST_PAD_PAD_TEMPLATE (pad)) {
    const GstCaps *templ_caps =
        GST_PAD_TEMPLATE_CAPS (GST_PAD_PAD_TEMPLATE (pad));
    if (!gst_caps_is_subset (result, templ_caps)) {
      GstCaps *temp;

      GST_CAT_ERROR_OBJECT (GST_CAT_CAPS, pad,
          "pad returned caps %" GST_PTR_FORMAT
          " which are not a real subset of its template caps %"
          GST_PTR_FORMAT, result, templ_caps);
      g_warning
          ("pad %s:%s returned caps which are not a real "
          "subset of its template caps", GST_DEBUG_PAD_NAME (pad));
      temp = gst_caps_intersect (templ_caps, result);
      gst_caps_unref (result);
      result = temp;
    }
  }
  if (filter) {
    if (!gst_caps_is_subset (result, filter)) {
      GstCaps *temp;

      GST_CAT_ERROR_OBJECT (GST_CAT_CAPS, pad,
          "pad returned caps %" GST_PTR_FORMAT
          " which are not a real subset of the filter caps %"
          GST_PTR_FORMAT, result, filter);
      g_warning ("pad %s:%s returned caps which are not a real "
          "subset of the filter caps", GST_DEBUG_PAD_NAME (pad));
      /* FIXME: Order? But shouldn't happen anyway... */
      temp = gst_caps_intersect_full (filter, result, GST_CAPS_INTERSECT_FIRST);
      gst_caps_unref (result);
      result = temp;
    }
  }
#endif

  return result;

  /* ERRORS */
null_caps:
  {
    g_critical ("pad %s:%s returned NULL caps from getcaps function",
        GST_DEBUG_PAD_NAME (pad));
    return NULL;
  }
}

/* should be called with the pad LOCK held */
/* refs the caps, so caller is responsible for getting it unreffed */
static GstCaps *
gst_pad_get_caps_unlocked (GstPad * pad, GstCaps * filter)
{
  GstCaps *result = NULL;
  GstPadTemplate *templ;
  gboolean fixed_caps;

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "get pad caps");

  fixed_caps = GST_PAD_IS_FIXED_CAPS (pad);

  if (fixed_caps) {
    /* fixed caps, try the negotiated caps first */
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "fixed pad caps: trying pad caps");
    if ((result = get_pad_caps (pad)))
      goto filter_done;
  }

  /* try the getcaps function next */
  if ((result = caps_with_getcaps (pad, filter)))
    goto done;

  if ((templ = GST_PAD_PAD_TEMPLATE (pad))) {
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "trying pad template caps");
    if ((result = GST_PAD_TEMPLATE_CAPS (templ)))
      goto filter_done;
  }

  if (!fixed_caps) {
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
        "non-fixed pad caps: trying pad caps");
    /* non fixed caps, try the negotiated caps */
    if ((result = get_pad_caps (pad)))
      goto filter_done;
  }

  /* this almost never happens */
  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "pad has no caps");
  result = gst_caps_new_empty ();
  goto done;

filter_done:
  /* run the filter on the result */
  if (filter) {
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
        "using caps %p %" GST_PTR_FORMAT " with filter %p %"
        GST_PTR_FORMAT, result, result, filter, filter);
    result = gst_caps_intersect_full (filter, result, GST_CAPS_INTERSECT_FIRST);
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "result %p %" GST_PTR_FORMAT,
        result, result);
  } else {
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
        "using caps %p %" GST_PTR_FORMAT, result, result);
    result = gst_caps_ref (result);
  }
done:
  return result;
}

/**
 * gst_pad_has_current_caps:
 * @pad: a  #GstPad to check
 *
 * Check if @pad has caps set on it with a #GST_EVENT_CAPS event.
 *
 * Returns: TRUE when @pad has caps associated with it.
 */
gboolean
gst_pad_has_current_caps (GstPad * pad)
{
  gboolean result;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_OBJECT_LOCK (pad);
  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "check current pad caps");
  result = (get_pad_caps (pad) != NULL);
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/**
 * gst_pad_get_current_caps:
 * @pad: a  #GstPad to get the current capabilities of.
 *
 * Gets the capabilities currently configured on @pad with the last
 * #GST_EVENT_CAPS event.
 *
 * Returns: the current caps of the pad with incremented ref-count.
 */
GstCaps *
gst_pad_get_current_caps (GstPad * pad)
{
  GstCaps *result;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  GST_OBJECT_LOCK (pad);
  if ((result = get_pad_caps (pad)))
    gst_caps_ref (result);
  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
      "get current pad caps %" GST_PTR_FORMAT, result);
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/**
 * gst_pad_get_caps:
 * @pad: a  #GstPad to get the capabilities of.
 * @filter: suggested #GstCaps.
 *
 * Gets the capabilities this pad can produce or consume.
 * Note that this method doesn't necessarily return the caps set by
 * gst_pad_set_caps() - use gst_pad_get_current_caps() for that instead.
 * gst_pad_get_caps returns all possible caps a pad can operate with, using
 * the pad's get_caps function;
 * this returns the pad template caps if not explicitly set.
 *
 * When called on sinkpads @filter contains the caps that
 * upstream could produce in the order preferred by upstream. When
 * called on srcpads @filter contains the caps accepted by
 * downstream in the preffered order. @filter might be %NULL but
 * if it is not %NULL the returned caps will be a subset of @filter.
 *
 * Note that this function does not return writable #GstCaps, use
 * gst_caps_make_writable() before modifying the caps.
 *
 * Returns: the caps of the pad with incremented ref-count.
 */
GstCaps *
gst_pad_get_caps (GstPad * pad, GstCaps * filter)
{
  GstCaps *result = NULL;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  g_return_val_if_fail (filter == NULL || GST_IS_CAPS (filter), NULL);

  GST_OBJECT_LOCK (pad);

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "get pad caps");

  result = gst_pad_get_caps_unlocked (pad, filter);

  GST_OBJECT_UNLOCK (pad);

  return result;
}


/**
 * gst_pad_peer_get_caps:
 * @pad: a  #GstPad to get the capabilities of.
 * @filter: a #GstCaps filter.
 *
 * Gets the capabilities of the peer connected to this pad. Similar to
 * gst_pad_get_caps().
 *
 * When called on srcpads @filter contains the caps that
 * upstream could produce in the order preferred by upstream. When
 * called on sinkpads @filter contains the caps accepted by
 * downstream in the preffered order. @filter might be %NULL but
 * if it is not %NULL the returned caps will be a subset of @filter.
 *
 * Returns: the caps of the peer pad with incremented ref-count. This function
 * returns %NULL when there is no peer pad.
 */
GstCaps *
gst_pad_peer_get_caps (GstPad * pad, GstCaps * filter)
{
  GstPad *peerpad;
  GstCaps *result = NULL;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  g_return_val_if_fail (filter == NULL || GST_IS_CAPS (filter), NULL);

  GST_OBJECT_LOCK (pad);

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "get peer caps");

  peerpad = GST_PAD_PEER (pad);
  if (G_UNLIKELY (peerpad == NULL))
    goto no_peer;

  gst_object_ref (peerpad);
  GST_OBJECT_UNLOCK (pad);

  result = gst_pad_get_caps (peerpad, filter);

  gst_object_unref (peerpad);

  return result;

no_peer:
  {
    GST_OBJECT_UNLOCK (pad);
    return NULL;
  }
}

static void
gst_pad_fixate_caps_default (GstPad * pad, GstCaps * caps)
{
  /* default fixation */
  gst_caps_fixate (caps);
}

/**
 * gst_pad_fixate_caps:
 * @pad: a  #GstPad to fixate
 * @caps: the  #GstCaps to fixate
 *
 * Fixate a caps on the given pad. Modifies the caps in place, so you should
 * make sure that the caps are actually writable (see gst_caps_make_writable()).
 */
void
gst_pad_fixate_caps (GstPad * pad, GstCaps * caps)
{
  GstPadFixateCapsFunction fixatefunc;

  g_return_if_fail (GST_IS_PAD (pad));
  g_return_if_fail (caps != NULL);
  g_return_if_fail (!gst_caps_is_empty (caps));
  g_return_if_fail (!gst_caps_is_any (caps));

  if (gst_caps_is_fixed (caps) || gst_caps_is_any (caps))
    return;

  g_return_if_fail (gst_caps_is_writable (caps));

  if (G_LIKELY ((fixatefunc = GST_PAD_FIXATECAPSFUNC (pad))))
    fixatefunc (pad, caps);
}

/* Default accept caps implementation just checks against
 * against the allowed caps for the pad */
static gboolean
gst_pad_acceptcaps_default (GstPad * pad, GstCaps * caps)
{
  /* get the caps and see if it intersects to something not empty */
  GstCaps *allowed;
  gboolean result = FALSE;

  GST_DEBUG_OBJECT (pad, "caps %" GST_PTR_FORMAT, caps);

  allowed = gst_pad_get_caps (pad, NULL);
  if (!allowed)
    goto nothing_allowed;

  GST_DEBUG_OBJECT (pad, "allowed caps %" GST_PTR_FORMAT, allowed);

  result = gst_caps_can_intersect (allowed, caps);

  gst_caps_unref (allowed);

  return result;

  /* ERRORS */
nothing_allowed:
  {
    GST_DEBUG_OBJECT (pad, "no caps allowed on the pad");
    return FALSE;
  }
}

/**
 * gst_pad_accept_caps:
 * @pad: a #GstPad to check
 * @caps: a #GstCaps to check on the pad
 *
 * Check if the given pad accepts the caps.
 *
 * Returns: TRUE if the pad can accept the caps.
 */
gboolean
gst_pad_accept_caps (GstPad * pad, GstCaps * caps)
{
  gboolean result;
  GstPadAcceptCapsFunction acceptfunc;
#if 0
  GstCaps *existing = NULL;
#endif

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  /* any pad can be unnegotiated */
  if (caps == NULL)
    return TRUE;

  /* lock for checking the existing caps */
  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "accept caps of %p", caps);
#if 0
  GST_OBJECT_LOCK (pad);
  /* The current caps on a pad are trivially acceptable */
  if (G_LIKELY ((existing = GST_PAD_CAPS (pad)))) {
    if (caps == existing || gst_caps_is_equal (caps, existing))
      goto is_same_caps;
  }
  GST_OBJECT_UNLOCK (pad);
#endif
  acceptfunc = GST_PAD_ACCEPTCAPSFUNC (pad);

  /* Only null if the element explicitly unset it */
  if (G_UNLIKELY (acceptfunc == NULL))
    goto no_func;

  /* we can call the function */
  result = acceptfunc (pad, caps);
  GST_DEBUG_OBJECT (pad, "acceptfunc returned %d", result);

  return result;

#if 0
is_same_caps:
  {
    GST_DEBUG_OBJECT (pad, "pad had same caps");
    GST_OBJECT_UNLOCK (pad);
    return TRUE;
  }
#endif
no_func:
  {
    GST_DEBUG_OBJECT (pad, "no acceptcaps function");
    return FALSE;
  }
}

/**
 * gst_pad_peer_accept_caps:
 * @pad: a  #GstPad to check the peer of
 * @caps: a #GstCaps to check on the pad
 *
 * Check if the peer of @pad accepts @caps. If @pad has no peer, this function
 * returns TRUE.
 *
 * Returns: TRUE if the peer of @pad can accept the caps or @pad has no peer.
 */
gboolean
gst_pad_peer_accept_caps (GstPad * pad, GstCaps * caps)
{
  GstPad *peerpad;
  gboolean result;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_OBJECT_LOCK (pad);

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "peer accept caps of (%p)", pad);

  peerpad = GST_PAD_PEER (pad);
  if (G_UNLIKELY (peerpad == NULL))
    goto no_peer;

  gst_object_ref (peerpad);
  /* release lock before calling external methods but keep ref to pad */
  GST_OBJECT_UNLOCK (pad);

  result = gst_pad_accept_caps (peerpad, caps);

  gst_object_unref (peerpad);

  return result;

no_peer:
  {
    GST_OBJECT_UNLOCK (pad);
    return TRUE;
  }
}

/**
 * gst_pad_set_caps:
 * @pad: a  #GstPad to set the capabilities of.
 * @caps: (transfer none): a #GstCaps to set.
 *
 * Sets the capabilities of this pad. The caps must be fixed. Any previous
 * caps on the pad will be unreffed. This function refs the caps so you should
 * unref if as soon as you don't need it anymore.
 * It is possible to set NULL caps, which will make the pad unnegotiated
 * again.
 *
 * Returns: TRUE if the caps could be set. FALSE if the caps were not fixed
 * or bad parameters were provided to this function.
 *
 * MT safe.
 */
gboolean
gst_pad_set_caps (GstPad * pad, GstCaps * caps)
{
  GstEvent *event;
  gboolean res = TRUE;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (caps != NULL && gst_caps_is_fixed (caps), FALSE);

  event = gst_event_new_caps (caps);

  if (GST_PAD_IS_SRC (pad))
    res = gst_pad_push_event (pad, event);
  else
    res = gst_pad_send_event (pad, event);

  return res;
}

static gboolean
do_event_function (GstPad * pad, GstEvent * event,
    GstPadEventFunction eventfunc, gboolean * caps_notify)
{
  gboolean result = TRUE, call_event = TRUE;
  GstCaps *caps, *templ, *old;

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_CAPS:
    {
      /* backwards compatibility mode for caps */
      gst_event_parse_caps (event, &caps);

      /* See if pad accepts the caps */
      templ = gst_pad_get_pad_template_caps (pad);
      if (!gst_caps_can_intersect (caps, templ))
        goto not_accepted;

      /* check if it changed */
      if ((old = gst_pad_get_current_caps (pad))) {
        call_event = !gst_caps_is_equal (caps, old);
        gst_caps_unref (old);
      }
      if (call_event)
        *caps_notify = TRUE;

      gst_caps_unref (templ);
      break;
    }
    default:
      break;
  }

  if (call_event) {
    GST_DEBUG_OBJECT (pad, "calling event function with event %p", event);
    result = eventfunc (pad, event);
  } else {
    gst_event_unref (event);
  }
  return result;

  /* ERRORS */
not_accepted:
  {
    gst_caps_unref (templ);
    gst_event_unref (event);
    GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad,
        "caps %" GST_PTR_FORMAT " not accepted", caps);
    return FALSE;
  }
}

/* function to send all pending events on the sinkpad to the event
 * function and collect the results. This function should be called with
 * the object lock. The object lock might be released by this function.
 */
static GstFlowReturn
gst_pad_update_events (GstPad * pad)
{
  GstFlowReturn ret = GST_FLOW_OK;
  guint i;
  GstPadEventFunction eventfunc;
  GstEvent *event;
  gboolean caps_notify = FALSE;

  if (G_UNLIKELY ((eventfunc = GST_PAD_EVENTFUNC (pad)) == NULL))
    goto no_function;

  for (i = 0; i < GST_EVENT_MAX_STICKY; i++) {
    gboolean res;
    PadEvent *ev;

    ev = &pad->priv->events[i];

    /* skip without pending event */
    if ((event = gst_event_steal (&ev->pending)) == NULL)
      continue;

    gst_event_ref (event);
    GST_OBJECT_UNLOCK (pad);

    res = do_event_function (pad, event, eventfunc, &caps_notify);

    /* things could have changed while we release the lock, check if we still
     * are handling the same event, if we don't something changed and we have
     * to try again. FIXME. we need a cookie here. FIXME, we also want to remove
     * that lock eventually and then do the retry elsewhere. */

    if (res) {
      /* make the event active */
      gst_event_take (&ev->event, event);

      /* notify caps change when needed */
      if (caps_notify) {
        g_object_notify_by_pspec ((GObject *) pad, pspec_caps);
        caps_notify = FALSE;
      }
    } else {
      gst_event_unref (event);
      ret = GST_FLOW_ERROR;
    }
    GST_OBJECT_LOCK (pad);
  }
  /* when we get here all events were successfully updated. */
  return ret;

  /* ERRORS */
no_function:
  {
    g_warning ("pad %s:%s has no event handler, file a bug.",
        GST_DEBUG_PAD_NAME (pad));
    return GST_FLOW_NOT_SUPPORTED;
  }
}

/**
 * gst_pad_get_pad_template_caps:
 * @pad: a #GstPad to get the template capabilities from.
 *
 * Gets the capabilities for @pad's template.
 *
 * Returns: (transfer full): the #GstCaps of this pad template.
 * Unref after usage.
 */
GstCaps *
gst_pad_get_pad_template_caps (GstPad * pad)
{
  static GstStaticCaps anycaps = GST_STATIC_CAPS ("ANY");

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  if (GST_PAD_PAD_TEMPLATE (pad))
    return gst_pad_template_get_caps (GST_PAD_PAD_TEMPLATE (pad));

  return gst_static_caps_get (&anycaps);
}

/**
 * gst_pad_get_peer:
 * @pad: a #GstPad to get the peer of.
 *
 * Gets the peer of @pad. This function refs the peer pad so
 * you need to unref it after use.
 *
 * Returns: (transfer full): the peer #GstPad. Unref after usage.
 *
 * MT safe.
 */
GstPad *
gst_pad_get_peer (GstPad * pad)
{
  GstPad *result;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  GST_OBJECT_LOCK (pad);
  result = GST_PAD_PEER (pad);
  if (result)
    gst_object_ref (result);
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/**
 * gst_pad_get_allowed_caps:
 * @pad: a #GstPad.
 *
 * Gets the capabilities of the allowed media types that can flow through
 * @pad and its peer.
 *
 * The allowed capabilities is calculated as the intersection of the results of
 * calling gst_pad_get_caps() on @pad and its peer. The caller owns a reference
 * on the resulting caps.
 *
 * Returns: (transfer full): the allowed #GstCaps of the pad link. Unref the
 *     caps when you no longer need it. This function returns NULL when @pad
 *     has no peer.
 *
 * MT safe.
 */
GstCaps *
gst_pad_get_allowed_caps (GstPad * pad)
{
  GstCaps *mycaps;
  GstCaps *caps;
  GstCaps *peercaps;
  GstPad *peer;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  GST_OBJECT_LOCK (pad);
  peer = GST_PAD_PEER (pad);
  if (G_UNLIKELY (peer == NULL))
    goto no_peer;

  GST_CAT_DEBUG_OBJECT (GST_CAT_PROPERTIES, pad, "getting allowed caps");

  gst_object_ref (peer);
  GST_OBJECT_UNLOCK (pad);
  mycaps = gst_pad_get_caps (pad, NULL);

  peercaps = gst_pad_get_caps (peer, NULL);
  gst_object_unref (peer);

  caps = gst_caps_intersect (mycaps, peercaps);
  gst_caps_unref (peercaps);
  gst_caps_unref (mycaps);

  GST_CAT_DEBUG_OBJECT (GST_CAT_CAPS, pad, "allowed caps %" GST_PTR_FORMAT,
      caps);

  return caps;

no_peer:
  {
    GST_CAT_DEBUG_OBJECT (GST_CAT_PROPERTIES, pad, "no peer");
    GST_OBJECT_UNLOCK (pad);

    return NULL;
  }
}

/**
 * gst_pad_iterate_internal_links_default:
 * @pad: the #GstPad to get the internal links of.
 *
 * Iterate the list of pads to which the given pad is linked to inside of
 * the parent element.
 * This is the default handler, and thus returns an iterator of all of the
 * pads inside the parent element with opposite direction.
 *
 * The caller must free this iterator after use with gst_iterator_free().
 *
 * Returns: a #GstIterator of #GstPad, or NULL if @pad has no parent. Unref each
 * returned pad with gst_object_unref().
 *
 * Since: 0.10.21
 */
GstIterator *
gst_pad_iterate_internal_links_default (GstPad * pad)
{
  GstIterator *res;
  GList **padlist;
  guint32 *cookie;
  GMutex *lock;
  gpointer owner;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  {
    GstElement *parent;

    GST_OBJECT_LOCK (pad);
    parent = GST_PAD_PARENT (pad);
    if (!parent || !GST_IS_ELEMENT (parent))
      goto no_parent;

    gst_object_ref (parent);
    GST_OBJECT_UNLOCK (pad);

    if (pad->direction == GST_PAD_SRC)
      padlist = &parent->sinkpads;
    else
      padlist = &parent->srcpads;

    GST_DEBUG_OBJECT (pad, "Making iterator");

    cookie = &parent->pads_cookie;
    owner = parent;
    lock = GST_OBJECT_GET_LOCK (parent);
  }

  res = gst_iterator_new_list (GST_TYPE_PAD,
      lock, cookie, padlist, (GObject *) owner, NULL);

  gst_object_unref (owner);

  return res;

  /* ERRORS */
no_parent:
  {
    GST_OBJECT_UNLOCK (pad);
    GST_DEBUG_OBJECT (pad, "no parent element");
    return NULL;
  }
}

/**
 * gst_pad_iterate_internal_links:
 * @pad: the GstPad to get the internal links of.
 *
 * Gets an iterator for the pads to which the given pad is linked to inside
 * of the parent element.
 *
 * Each #GstPad element yielded by the iterator will have its refcount increased,
 * so unref after use.
 *
 * Free-function: gst_iterator_free
 *
 * Returns: (transfer full): a new #GstIterator of #GstPad or %NULL when the
 *     pad does not have an iterator function configured. Use
 *     gst_iterator_free() after usage.
 *
 * Since: 0.10.21
 */
GstIterator *
gst_pad_iterate_internal_links (GstPad * pad)
{
  GstIterator *res = NULL;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  if (GST_PAD_ITERINTLINKFUNC (pad))
    res = GST_PAD_ITERINTLINKFUNC (pad) (pad);

  return res;
}

/**
 * gst_pad_forward:
 * @pad: a #GstPad
 * @forward: a #GstPadForwardFunction
 * @user_data: user data passed to @forward
 *
 * Calls @forward for all internally linked pads of @pad. This function deals with
 * dynamically changing internal pads and will make sure that the @forward
 * function is only called once for each pad.
 *
 * When @forward returns TRUE, no further pads will be processed.
 *
 * Returns: TRUE if one of the dispatcher functions returned TRUE.
 */
gboolean
gst_pad_forward (GstPad * pad, GstPadForwardFunction forward,
    gpointer user_data)
{
  gboolean result = FALSE;
  GstIterator *iter;
  gboolean done = FALSE;
  GValue item = { 0, };
  GList *pushed_pads = NULL;

  iter = gst_pad_iterate_internal_links (pad);

  if (!iter)
    goto no_iter;

  while (!done) {
    switch (gst_iterator_next (iter, &item)) {
      case GST_ITERATOR_OK:
      {
        GstPad *intpad;

        intpad = g_value_get_object (&item);

        /* if already pushed, skip. FIXME, find something faster to tag pads */
        if (g_list_find (pushed_pads, intpad)) {
          g_value_reset (&item);
          break;
        }

        GST_LOG_OBJECT (pad, "calling forward function on pad %s:%s",
            GST_DEBUG_PAD_NAME (intpad));
        done = result = forward (intpad, user_data);

        pushed_pads = g_list_prepend (pushed_pads, intpad);

        g_value_reset (&item);
        break;
      }
      case GST_ITERATOR_RESYNC:
        /* We don't reset the result here because we don't push the event
         * again on pads that got the event already and because we need
         * to consider the result of the previous pushes */
        gst_iterator_resync (iter);
        break;
      case GST_ITERATOR_ERROR:
        GST_ERROR_OBJECT (pad, "Could not iterate over internally linked pads");
        done = TRUE;
        break;
      case GST_ITERATOR_DONE:
        done = TRUE;
        break;
    }
  }
  g_value_unset (&item);
  gst_iterator_free (iter);

  g_list_free (pushed_pads);

no_iter:
  return result;
}

typedef struct
{
  GstEvent *event;
  gboolean result;
  gboolean dispatched;
} EventData;

static gboolean
event_forward_func (GstPad * pad, EventData * data)
{
  /* for each pad we send to, we should ref the event; it's up
   * to downstream to unref again when handled. */
  GST_LOG_OBJECT (pad, "Reffing and pushing event %p (%s) to %s:%s",
      data->event, GST_EVENT_TYPE_NAME (data->event), GST_DEBUG_PAD_NAME (pad));

  data->result |= gst_pad_push_event (pad, gst_event_ref (data->event));

  data->dispatched = TRUE;

  /* don't stop */
  return FALSE;
}

/**
 * gst_pad_event_default:
 * @pad: a #GstPad to call the default event handler on.
 * @event: (transfer full): the #GstEvent to handle.
 *
 * Invokes the default event handler for the given pad.
 *
 * The EOS event will pause the task associated with @pad before it is forwarded
 * to all internally linked pads,
 *
 * The CAPS event will never be forwarded.
 *
 * The the event is sent to all pads internally linked to @pad. This function
 * takes ownership of @event.
 *
 * Returns: TRUE if the event was sent succesfully.
 */
gboolean
gst_pad_event_default (GstPad * pad, GstEvent * event)
{
  gboolean result;
  EventData data;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);

  GST_LOG_OBJECT (pad, "default event handler");

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_EOS:
    {
      GST_DEBUG_OBJECT (pad, "pausing task because of eos");
      gst_pad_pause_task (pad);
      break;
    }
    default:
      break;
  }

  data.event = event;
  data.dispatched = FALSE;
  data.result = FALSE;

  gst_pad_forward (pad, (GstPadForwardFunction) event_forward_func, &data);

  /* for sinkpads without a parent element or without internal links, nothing
   * will be dispatched but we still want to return TRUE. */
  if (data.dispatched)
    result = data.result;
  else
    result = TRUE;

  gst_event_unref (event);

  return result;
}

/**
 * gst_pad_query:
 * @pad: a #GstPad to invoke the default query on.
 * @query: (transfer none): the #GstQuery to perform.
 *
 * Dispatches a query to a pad. The query should have been allocated by the
 * caller via one of the type-specific allocation functions. The element that
 * the pad belongs to is responsible for filling the query with an appropriate
 * response, which should then be parsed with a type-specific query parsing
 * function.
 *
 * Again, the caller is responsible for both the allocation and deallocation of
 * the query structure.
 *
 * Please also note that some queries might need a running pipeline to work.
 *
 * Returns: TRUE if the query could be performed.
 */
gboolean
gst_pad_query (GstPad * pad, GstQuery * query)
{
  gboolean res;
  GstPadQueryFunction func;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_IS_QUERY (query), FALSE);

  GST_DEBUG_OBJECT (pad, "sending query %p (%s)", query,
      GST_QUERY_TYPE_NAME (query));

  if ((func = GST_PAD_QUERYFUNC (pad)) == NULL)
    goto no_func;

  res = func (pad, query);

  GST_DEBUG_OBJECT (pad, "sent query %p (%s), result %d", query,
      GST_QUERY_TYPE_NAME (query), res);

  return res;

no_func:
  {
    GST_DEBUG_OBJECT (pad, "had no query function");
    return FALSE;
  }
}

/**
 * gst_pad_peer_query:
 * @pad: a #GstPad to invoke the peer query on.
 * @query: (transfer none): the #GstQuery to perform.
 *
 * Performs gst_pad_query() on the peer of @pad.
 *
 * The caller is responsible for both the allocation and deallocation of
 * the query structure.
 *
 * Returns: TRUE if the query could be performed. This function returns %FALSE
 * if @pad has no peer.
 *
 * Since: 0.10.15
 */
gboolean
gst_pad_peer_query (GstPad * pad, GstQuery * query)
{
  GstPad *peerpad;
  gboolean result;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (GST_IS_QUERY (query), FALSE);

  GST_OBJECT_LOCK (pad);

  GST_DEBUG_OBJECT (pad, "peer query %p (%s)", query,
      GST_QUERY_TYPE_NAME (query));

  peerpad = GST_PAD_PEER (pad);
  if (G_UNLIKELY (peerpad == NULL))
    goto no_peer;

  gst_object_ref (peerpad);
  GST_OBJECT_UNLOCK (pad);

  result = gst_pad_query (peerpad, query);

  gst_object_unref (peerpad);

  return result;

  /* ERRORS */
no_peer:
  {
    GST_WARNING_OBJECT (pad, "pad has no peer");
    GST_OBJECT_UNLOCK (pad);
    return FALSE;
  }
}

/**
 * gst_pad_query_default:
 * @pad: a #GstPad to call the default query handler on.
 * @query: (transfer none): the #GstQuery to handle.
 *
 * Invokes the default query handler for the given pad.
 * The query is sent to all pads internally linked to @pad. Note that
 * if there are many possible sink pads that are internally linked to
 * @pad, only one will be sent the query.
 * Multi-sinkpad elements should implement custom query handlers.
 *
 * Returns: TRUE if the query was performed succesfully.
 */
gboolean
gst_pad_query_default (GstPad * pad, GstQuery * query)
{
  gboolean forward = TRUE, ret = FALSE;

  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_SCHEDULING:
      forward = FALSE;
      break;
    case GST_QUERY_POSITION:
    case GST_QUERY_SEEKING:
    case GST_QUERY_FORMATS:
    case GST_QUERY_LATENCY:
    case GST_QUERY_JITTER:
    case GST_QUERY_RATE:
    case GST_QUERY_CONVERT:
    case GST_QUERY_ALLOCATION:
    default:
      break;
  }

  if (forward) {
    ret = gst_pad_forward
        (pad, (GstPadForwardFunction) gst_pad_peer_query, query);
  }
  return ret;
}

static void
probe_hook_marshal (GHook * hook, ProbeMarshall * data)
{
  GstPad *pad = data->pad;
  GstProbeType flags;
  GstPadProbeCallback callback;
  GstProbeReturn ret;

  /* if we have called this callback, do nothing */
  if (PROBE_COOKIE (hook) == data->cookie)
    return;

  PROBE_COOKIE (hook) = data->cookie;

  flags = hook->flags >> G_HOOK_FLAG_USER_SHIFT;

  /* one of the data types */
  if ((flags & GST_PROBE_TYPE_DATA & data->mask) == 0)
    return;
  /* one of the scheduling types */
  if ((flags & GST_PROBE_TYPE_SCHEDULING & data->mask) == 0)
    return;
  /* all of the blocking types must match */
  if ((flags & GST_PROBE_TYPE_BLOCKING) !=
      (data->mask & GST_PROBE_TYPE_BLOCKING))
    return;

  GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
      "hook %lu with flags 0x%08x matches", hook->hook_id, flags);

  callback = (GstPadProbeCallback) hook->func;
  if (callback == NULL)
    return;

  GST_OBJECT_UNLOCK (pad);

  ret = callback (pad, data->mask, data->type_data, hook->data);

  GST_OBJECT_LOCK (pad);

  switch (ret) {
    case GST_PROBE_REMOVE:
      /* remove the probe */
      GST_DEBUG_OBJECT (pad, "asked to remove hook");
      cleanup_hook (pad, hook);
      break;
    case GST_PROBE_DROP:
      /* need to drop the data, make sure other probes don't get called
       * anymore */
      GST_DEBUG_OBJECT (pad, "asked to drop item");
      data->mask = GST_PROBE_TYPE_INVALID;
      data->ret = GST_PROBE_DROP;
      break;
    case GST_PROBE_PASS:
      /* inform the pad block to let things pass */
      GST_DEBUG_OBJECT (pad, "asked to pass item");
      data->pass = TRUE;
      break;
    default:
      GST_DEBUG_OBJECT (pad, "probe returned %d", ret);
      break;
  }
}

#define PROBE(pad,mask,data,label)                \
  G_STMT_START {                                  \
    if (G_UNLIKELY (pad->num_probes)) {           \
      ret = do_probe_callbacks (pad, mask, data); \
      if (G_UNLIKELY (ret != GST_FLOW_OK))        \
        goto label;                               \
    }                                             \
  } G_STMT_END

static GstFlowReturn
do_probe_callbacks (GstPad * pad, GstProbeType mask, gpointer type_data)
{
  ProbeMarshall data;
  guint cookie;

  data.pad = pad;
  data.mask = mask;
  data.type_data = type_data;
  data.ret = GST_PROBE_OK;
  data.pass = FALSE;
  data.cookie = pad->priv->probe_cookie++;

again:
  cookie = pad->priv->probe_cookie;

  g_hook_list_marshal (&pad->probes, FALSE,
      (GHookMarshaller) probe_hook_marshal, &data);

  /* if the list changed, call the new callbacks (they will not have their
   * cookie set to data.cookie */
  if (cookie != pad->priv->probe_cookie) {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "probe list changed, restarting");
    goto again;
  }

  if (data.ret == GST_PROBE_DROP)
    goto dropped;

  if (data.pass)
    goto passed;

  if (mask & GST_PROBE_TYPE_BLOCK) {
    while (GST_PAD_IS_BLOCKED (pad)) {
      GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
          "we are blocked %d times", pad->num_blocked);

      /* we might have released the lock */
      if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
        goto flushing;

      /* now we block the streaming thread. It can be unlocked when we
       * deactivate the pad (which will also set the FLUSHING flag) or
       * when the pad is unblocked. A flushing event will also unblock
       * the pad after setting the FLUSHING flag. */
      GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
          "Waiting to be unblocked or set flushing");
      GST_OBJECT_FLAG_SET (pad, GST_PAD_BLOCKING);
      GST_PAD_BLOCK_WAIT (pad);
      GST_OBJECT_FLAG_UNSET (pad, GST_PAD_BLOCKING);
      GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "We got unblocked");

      if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
        goto flushing;
    }
  }

  return GST_FLOW_OK;

  /* ERRORS */
flushing:
  {
    GST_DEBUG_OBJECT (pad, "pad is flushing");
    return GST_FLOW_WRONG_STATE;
  }
dropped:
  {
    GST_DEBUG_OBJECT (pad, "data is dropped");
    return GST_FLOW_CUSTOM_SUCCESS;
  }
passed:
  {
    GST_DEBUG_OBJECT (pad, "data is passed");
    return GST_FLOW_OK;
  }
}

/* pad offsets */

/**
 * gst_pad_get_offset:
 * @pad: a #GstPad
 *
 * Get the offset applied to the running time of @pad. @pad has to be a source
 * pad.
 *
 * Returns: the offset.
 */
gint64
gst_pad_get_offset (GstPad * pad)
{
  gint64 result;

  g_return_val_if_fail (GST_IS_PAD (pad), 0);

  GST_OBJECT_LOCK (pad);
  result = pad->offset;
  GST_OBJECT_UNLOCK (pad);

  return result;
}

/**
 * gst_pad_set_offset:
 * @pad: a #GstPad
 * @offset: the offset
 *
 * Set the offset that will be applied to the running time of @pad.
 */
void
gst_pad_set_offset (GstPad * pad, gint64 offset)
{
  guint idx;
  GstPad *peer;
  GstPad *tmp = NULL;

  g_return_if_fail (GST_IS_PAD (pad));

  GST_OBJECT_LOCK (pad);
  /* if nothing changed, do nothing */
  if (pad->offset == offset)
    goto done;

  pad->offset = offset;

  /* if no peer, we just updated the offset */
  if ((peer = GST_PAD_PEER (pad)) == NULL)
    goto done;

  /* switch pads around when dealing with a sinkpad */
  if (GST_PAD_IS_SINK (pad)) {
    /* ref the peer so it doesn't go away when we release the lock */
    tmp = gst_object_ref (peer);
    /* make sure we get the peer (the srcpad) */
    GST_OBJECT_UNLOCK (pad);

    /* swap pads */
    peer = pad;
    pad = tmp;

    GST_OBJECT_LOCK (pad);
    /* check if the pad didn't get relinked */
    if (GST_PAD_PEER (pad) != peer)
      goto done;

    /* we can release the ref now */
    gst_object_unref (peer);
  }

  /* the index of the segment event in the array */
  idx = GST_EVENT_STICKY_IDX_TYPE (GST_EVENT_SEGMENT);

  /* lock order is srcpad >> sinkpad */
  GST_OBJECT_LOCK (peer);
  /* take the current segment event, adjust it and then place
   * it on the sinkpad. events on the srcpad are always active. */
  if (replace_event (pad, peer, idx))
    GST_OBJECT_FLAG_SET (peer, GST_PAD_NEED_EVENTS);

  GST_OBJECT_UNLOCK (peer);

done:
  GST_OBJECT_UNLOCK (pad);
}


/**********************************************************************
 * Data passing functions
 */

/* this is the chain function that does not perform the additional argument
 * checking for that little extra speed.
 */
static inline GstFlowReturn
gst_pad_chain_data_unchecked (GstPad * pad, GstProbeType type, void *data)
{
  GstFlowReturn ret;
  gboolean needs_events;

  GST_PAD_STREAM_LOCK (pad);

  GST_OBJECT_LOCK (pad);
  if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
    goto flushing;

  needs_events = GST_PAD_NEEDS_EVENTS (pad);
  if (G_UNLIKELY (needs_events)) {
    GST_OBJECT_FLAG_UNSET (pad, GST_PAD_NEED_EVENTS);

    GST_DEBUG_OBJECT (pad, "need to update all events");
    ret = gst_pad_update_events (pad);
    if (G_UNLIKELY (ret != GST_FLOW_OK))
      goto events_error;
  }

  PROBE (pad, GST_PROBE_TYPE_PUSH | type, data, probe_stopped);

  GST_OBJECT_UNLOCK (pad);

  /* NOTE: we read the chainfunc unlocked.
   * we cannot hold the lock for the pad so we might send
   * the data to the wrong function. This is not really a
   * problem since functions are assigned at creation time
   * and don't change that often... */
  if (G_LIKELY (type & GST_PROBE_TYPE_BUFFER)) {
    GstPadChainFunction chainfunc;

    if (G_UNLIKELY ((chainfunc = GST_PAD_CHAINFUNC (pad)) == NULL))
      goto no_function;

    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "calling chainfunction &%s with buffer %p",
        GST_DEBUG_FUNCPTR_NAME (chainfunc), data);

    ret = chainfunc (pad, GST_BUFFER_CAST (data));

    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "called chainfunction &%s with buffer %p, returned %s",
        GST_DEBUG_FUNCPTR_NAME (chainfunc), data, gst_flow_get_name (ret));
  } else {
    GstPadChainListFunction chainlistfunc;

    if (G_UNLIKELY ((chainlistfunc = GST_PAD_CHAINLISTFUNC (pad)) == NULL))
      goto no_function;

    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "calling chainlistfunction &%s",
        GST_DEBUG_FUNCPTR_NAME (chainlistfunc));

    ret = chainlistfunc (pad, GST_BUFFER_LIST_CAST (data));

    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "called chainlistfunction &%s, returned %s",
        GST_DEBUG_FUNCPTR_NAME (chainlistfunc), gst_flow_get_name (ret));
  }

  GST_PAD_STREAM_UNLOCK (pad);

  return ret;

  /* ERRORS */
flushing:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "chaining, but pad was flushing");
    GST_OBJECT_UNLOCK (pad);
    GST_PAD_STREAM_UNLOCK (pad);
    return GST_FLOW_WRONG_STATE;
  }
events_error:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "events were not accepted");
    GST_OBJECT_UNLOCK (pad);
    GST_PAD_STREAM_UNLOCK (pad);
    return ret;
  }
probe_stopped:
  {
    GST_OBJECT_UNLOCK (pad);
    GST_PAD_STREAM_UNLOCK (pad);
    gst_mini_object_unref (GST_MINI_OBJECT_CAST (data));

    switch (ret) {
      case GST_FLOW_CUSTOM_SUCCESS:
        GST_DEBUG_OBJECT (pad, "dropped buffer");
        ret = GST_FLOW_OK;
        break;
      default:
        GST_DEBUG_OBJECT (pad, "en error occured %s", gst_flow_get_name (ret));
        break;
    }
    return ret;
  }
no_function:
  {
    gst_mini_object_unref (GST_MINI_OBJECT_CAST (data));
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "pushing, but not chainhandler");
    GST_ELEMENT_ERROR (GST_PAD_PARENT (pad), CORE, PAD, (NULL),
        ("push on pad %s:%s but it has no chainfunction",
            GST_DEBUG_PAD_NAME (pad)));
    GST_PAD_STREAM_UNLOCK (pad);
    return GST_FLOW_NOT_SUPPORTED;
  }
}

/**
 * gst_pad_chain:
 * @pad: a sink #GstPad, returns GST_FLOW_ERROR if not.
 * @buffer: (transfer full): the #GstBuffer to send, return GST_FLOW_ERROR
 *     if not.
 *
 * Chain a buffer to @pad.
 *
 * The function returns #GST_FLOW_WRONG_STATE if the pad was flushing.
 *
 * If the buffer type is not acceptable for @pad (as negotiated with a
 * preceeding GST_EVENT_CAPS event), this function returns
 * #GST_FLOW_NOT_NEGOTIATED.
 *
 * The function proceeds calling the chain function installed on @pad (see
 * gst_pad_set_chain_function()) and the return value of that function is
 * returned to the caller. #GST_FLOW_NOT_SUPPORTED is returned if @pad has no
 * chain function.
 *
 * In all cases, success or failure, the caller loses its reference to @buffer
 * after calling this function.
 *
 * Returns: a #GstFlowReturn from the pad.
 *
 * MT safe.
 */
GstFlowReturn
gst_pad_chain (GstPad * pad, GstBuffer * buffer)
{
  g_return_val_if_fail (GST_IS_PAD (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_PAD_IS_SINK (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_IS_BUFFER (buffer), GST_FLOW_ERROR);

  return gst_pad_chain_data_unchecked (pad, GST_PROBE_TYPE_BUFFER, buffer);
}

static GstFlowReturn
gst_pad_chain_list_default (GstPad * pad, GstBufferList * list)
{
  guint i, len;
  GstBuffer *buffer;
  GstFlowReturn ret;

  GST_INFO_OBJECT (pad, "chaining each group in list as a merged buffer");

  len = gst_buffer_list_len (list);

  ret = GST_FLOW_OK;
  for (i = 0; i < len; i++) {
    buffer = gst_buffer_list_get (list, i);
    ret =
        gst_pad_chain_data_unchecked (pad, GST_PROBE_TYPE_BUFFER,
        gst_buffer_ref (buffer));
    if (ret != GST_FLOW_OK)
      break;
  }
  gst_buffer_list_unref (list);

  return ret;
}

/**
 * gst_pad_chain_list:
 * @pad: a sink #GstPad, returns GST_FLOW_ERROR if not.
 * @list: (transfer full): the #GstBufferList to send, return GST_FLOW_ERROR
 *     if not.
 *
 * Chain a bufferlist to @pad.
 *
 * The function returns #GST_FLOW_WRONG_STATE if the pad was flushing.
 *
 * If @pad was not negotiated properly with a CAPS event, this function
 * returns #GST_FLOW_NOT_NEGOTIATED.
 *
 * The function proceeds calling the chainlist function installed on @pad (see
 * gst_pad_set_chain_list_function()) and the return value of that function is
 * returned to the caller. #GST_FLOW_NOT_SUPPORTED is returned if @pad has no
 * chainlist function.
 *
 * In all cases, success or failure, the caller loses its reference to @list
 * after calling this function.
 *
 * MT safe.
 *
 * Returns: a #GstFlowReturn from the pad.
 *
 * Since: 0.10.24
 */
GstFlowReturn
gst_pad_chain_list (GstPad * pad, GstBufferList * list)
{
  g_return_val_if_fail (GST_IS_PAD (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_PAD_IS_SINK (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_IS_BUFFER_LIST (list), GST_FLOW_ERROR);

  return gst_pad_chain_data_unchecked (pad, GST_PROBE_TYPE_BUFFER_LIST, list);
}

static GstFlowReturn
gst_pad_push_data (GstPad * pad, GstProbeType type, void *data)
{
  GstPad *peer;
  GstFlowReturn ret;

  GST_OBJECT_LOCK (pad);
  if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
    goto flushing;

  type |= GST_PROBE_TYPE_PUSH;

  /* do block probes */
  PROBE (pad, type | GST_PROBE_TYPE_BLOCK, data, probe_stopped);

  /* do post-blocking probes */
  PROBE (pad, type, data, probe_stopped);

  if (G_UNLIKELY ((peer = GST_PAD_PEER (pad)) == NULL))
    goto not_linked;

  /* take ref to peer pad before releasing the lock */
  gst_object_ref (peer);
  pad->priv->using++;
  GST_OBJECT_UNLOCK (pad);

  ret = gst_pad_chain_data_unchecked (peer, type, data);

  gst_object_unref (peer);

  GST_OBJECT_LOCK (pad);
  pad->priv->using--;
  if (pad->priv->using == 0) {
    /* pad is not active anymore, trigger idle callbacks */
    PROBE (pad, GST_PROBE_TYPE_PUSH | GST_PROBE_TYPE_IDLE, NULL, probe_stopped);
  }
  GST_OBJECT_UNLOCK (pad);

  return ret;

  /* ERROR recovery here */
  /* ERRORS */
flushing:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "pushing, but pad was flushing");
    GST_OBJECT_UNLOCK (pad);
    gst_mini_object_unref (GST_MINI_OBJECT_CAST (data));
    return GST_FLOW_WRONG_STATE;
  }
probe_stopped:
  {
    GST_OBJECT_UNLOCK (pad);
    gst_mini_object_unref (GST_MINI_OBJECT_CAST (data));

    switch (ret) {
      case GST_FLOW_CUSTOM_SUCCESS:
        GST_DEBUG_OBJECT (pad, "dropped buffer");
        ret = GST_FLOW_OK;
        break;
      default:
        GST_DEBUG_OBJECT (pad, "en error occured %s", gst_flow_get_name (ret));
        break;
    }
    return ret;
  }
not_linked:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "pushing, but it was not linked");
    GST_OBJECT_UNLOCK (pad);
    gst_mini_object_unref (GST_MINI_OBJECT_CAST (data));
    return GST_FLOW_NOT_LINKED;
  }
}

/**
 * gst_pad_push:
 * @pad: a source #GstPad, returns #GST_FLOW_ERROR if not.
 * @buffer: (transfer full): the #GstBuffer to push returns GST_FLOW_ERROR
 *     if not.
 *
 * Pushes a buffer to the peer of @pad.
 *
 * This function will call installed block probes before triggering any
 * installed data probes.
 *
 * The function proceeds calling gst_pad_chain() on the peer pad and returns
 * the value from that function. If @pad has no peer, #GST_FLOW_NOT_LINKED will
 * be returned.
 *
 * In all cases, success or failure, the caller loses its reference to @buffer
 * after calling this function.
 *
 * Returns: a #GstFlowReturn from the peer pad.
 *
 * MT safe.
 */
GstFlowReturn
gst_pad_push (GstPad * pad, GstBuffer * buffer)
{
  g_return_val_if_fail (GST_IS_PAD (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_PAD_IS_SRC (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_IS_BUFFER (buffer), GST_FLOW_ERROR);

  return gst_pad_push_data (pad, GST_PROBE_TYPE_BUFFER, buffer);
}

/**
 * gst_pad_push_list:
 * @pad: a source #GstPad, returns #GST_FLOW_ERROR if not.
 * @list: (transfer full): the #GstBufferList to push returns GST_FLOW_ERROR
 *     if not.
 *
 * Pushes a buffer list to the peer of @pad.
 *
 * This function will call installed block probes before triggering any
 * installed data probes.
 *
 * The function proceeds calling the chain function on the peer pad and returns
 * the value from that function. If @pad has no peer, #GST_FLOW_NOT_LINKED will
 * be returned. If the peer pad does not have any installed chainlist function
 * every group buffer of the list will be merged into a normal #GstBuffer and
 * chained via gst_pad_chain().
 *
 * In all cases, success or failure, the caller loses its reference to @list
 * after calling this function.
 *
 * Returns: a #GstFlowReturn from the peer pad.
 *
 * MT safe.
 *
 * Since: 0.10.24
 */
GstFlowReturn
gst_pad_push_list (GstPad * pad, GstBufferList * list)
{
  g_return_val_if_fail (GST_IS_PAD (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_PAD_IS_SRC (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_IS_BUFFER_LIST (list), GST_FLOW_ERROR);

  return gst_pad_push_data (pad, GST_PROBE_TYPE_BUFFER_LIST, list);
}

static GstFlowReturn
gst_pad_get_range_unchecked (GstPad * pad, guint64 offset, guint size,
    GstBuffer ** buffer)
{
  GstFlowReturn ret;
  GstPadGetRangeFunction getrangefunc;

  GST_PAD_STREAM_LOCK (pad);

  GST_OBJECT_LOCK (pad);
  if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
    goto flushing;
  GST_OBJECT_UNLOCK (pad);

  if (G_UNLIKELY ((getrangefunc = GST_PAD_GETRANGEFUNC (pad)) == NULL))
    goto no_function;

  GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
      "calling getrangefunc %s, offset %"
      G_GUINT64_FORMAT ", size %u",
      GST_DEBUG_FUNCPTR_NAME (getrangefunc), offset, size);

  ret = getrangefunc (pad, offset, size, buffer);

  if (G_UNLIKELY (ret != GST_FLOW_OK))
    goto get_range_failed;

  /* can only fire the signal if we have a valid buffer */
  GST_OBJECT_LOCK (pad);
  PROBE (pad, GST_PROBE_TYPE_PULL | GST_PROBE_TYPE_BUFFER, *buffer,
      probe_stopped);
  GST_OBJECT_UNLOCK (pad);

  GST_PAD_STREAM_UNLOCK (pad);

  return ret;

  /* ERRORS */
flushing:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "getrange, but pad was flushing");
    GST_OBJECT_UNLOCK (pad);
    GST_PAD_STREAM_UNLOCK (pad);
    return GST_FLOW_WRONG_STATE;
  }
no_function:
  {
    GST_ELEMENT_ERROR (GST_PAD_PARENT (pad), CORE, PAD, (NULL),
        ("getrange on pad %s:%s but it has no getrangefunction",
            GST_DEBUG_PAD_NAME (pad)));
    GST_PAD_STREAM_UNLOCK (pad);
    return GST_FLOW_NOT_SUPPORTED;
  }
probe_stopped:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "probe returned %s", gst_flow_get_name (ret));
    GST_OBJECT_UNLOCK (pad);
    GST_PAD_STREAM_UNLOCK (pad);
    gst_buffer_unref (*buffer);
    *buffer = NULL;
    return ret;
  }
get_range_failed:
  {
    GST_PAD_STREAM_UNLOCK (pad);
    *buffer = NULL;
    GST_CAT_LEVEL_LOG (GST_CAT_SCHEDULING,
        (ret >= GST_FLOW_UNEXPECTED) ? GST_LEVEL_INFO : GST_LEVEL_WARNING,
        pad, "getrange failed, flow: %s", gst_flow_get_name (ret));
    return ret;
  }
}

/**
 * gst_pad_get_range:
 * @pad: a src #GstPad, returns #GST_FLOW_ERROR if not.
 * @offset: The start offset of the buffer
 * @size: The length of the buffer
 * @buffer: (out callee-allocates): a pointer to hold the #GstBuffer,
 *     returns #GST_FLOW_ERROR if %NULL.
 *
 * When @pad is flushing this function returns #GST_FLOW_WRONG_STATE
 * immediatly and @buffer is %NULL.
 *
 * Calls the getrange function of @pad, see #GstPadGetRangeFunction for a
 * description of a getrange function. If @pad has no getrange function
 * installed (see gst_pad_set_getrange_function()) this function returns
 * #GST_FLOW_NOT_SUPPORTED.
 *
 * This is a lowlevel function. Usualy gst_pad_pull_range() is used.
 *
 * Returns: a #GstFlowReturn from the pad.
 *
 * MT safe.
 */
GstFlowReturn
gst_pad_get_range (GstPad * pad, guint64 offset, guint size,
    GstBuffer ** buffer)
{
  g_return_val_if_fail (GST_IS_PAD (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_PAD_IS_SRC (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (buffer != NULL, GST_FLOW_ERROR);

  return gst_pad_get_range_unchecked (pad, offset, size, buffer);
}

/**
 * gst_pad_pull_range:
 * @pad: a sink #GstPad, returns GST_FLOW_ERROR if not.
 * @offset: The start offset of the buffer
 * @size: The length of the buffer
 * @buffer: (out callee-allocates): a pointer to hold the #GstBuffer, returns
 *     GST_FLOW_ERROR if %NULL.
 *
 * Pulls a @buffer from the peer pad.
 *
 * This function will first trigger the pad block signal if it was
 * installed.
 *
 * When @pad is not linked #GST_FLOW_NOT_LINKED is returned else this
 * function returns the result of gst_pad_get_range() on the peer pad.
 * See gst_pad_get_range() for a list of return values and for the
 * semantics of the arguments of this function.
 *
 * Returns: a #GstFlowReturn from the peer pad.
 * When this function returns #GST_FLOW_OK, @buffer will contain a valid
 * #GstBuffer that should be freed with gst_buffer_unref() after usage.
 * @buffer may not be used or freed when any other return value than
 * #GST_FLOW_OK is returned.
 *
 * MT safe.
 */
GstFlowReturn
gst_pad_pull_range (GstPad * pad, guint64 offset, guint size,
    GstBuffer ** buffer)
{
  GstPad *peer;
  GstFlowReturn ret;
  gboolean needs_events;

  g_return_val_if_fail (GST_IS_PAD (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (GST_PAD_IS_SINK (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (buffer != NULL, GST_FLOW_ERROR);

  GST_OBJECT_LOCK (pad);
  if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
    goto flushing;

  PROBE (pad, GST_PROBE_TYPE_PULL | GST_PROBE_TYPE_BLOCK, NULL,
      pre_probe_stopped);

  if (G_UNLIKELY ((peer = GST_PAD_PEER (pad)) == NULL))
    goto not_linked;

  gst_object_ref (peer);
  pad->priv->using++;
  GST_OBJECT_UNLOCK (pad);

  ret = gst_pad_get_range_unchecked (peer, offset, size, buffer);

  gst_object_unref (peer);

  GST_OBJECT_LOCK (pad);
  pad->priv->using--;
  if (pad->priv->using == 0) {
    /* pad is not active anymore, trigger idle callbacks */
    PROBE (pad, GST_PROBE_TYPE_PULL | GST_PROBE_TYPE_IDLE, NULL,
        post_probe_stopped);
  }

  if (G_UNLIKELY (ret != GST_FLOW_OK))
    goto pull_range_failed;

  PROBE (pad, GST_PROBE_TYPE_PULL | GST_PROBE_TYPE_BUFFER, buffer,
      post_probe_stopped);

  needs_events = GST_PAD_NEEDS_EVENTS (pad);
  if (G_UNLIKELY (needs_events)) {
    GST_OBJECT_FLAG_UNSET (pad, GST_PAD_NEED_EVENTS);

    GST_DEBUG_OBJECT (pad, "we need to update the events");
    ret = gst_pad_update_events (pad);
    if (G_UNLIKELY (ret != GST_FLOW_OK))
      goto events_error;
  }
  GST_OBJECT_UNLOCK (pad);

  return ret;

  /* ERROR recovery here */
flushing:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "pullrange, but pad was flushing");
    GST_OBJECT_UNLOCK (pad);
    return GST_FLOW_WRONG_STATE;
  }
pre_probe_stopped:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "pre probe returned %s",
        gst_flow_get_name (ret));
    GST_OBJECT_UNLOCK (pad);
    return ret;
  }
not_linked:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "pulling range, but it was not linked");
    GST_OBJECT_UNLOCK (pad);
    return GST_FLOW_NOT_LINKED;
  }
pull_range_failed:
  {
    *buffer = NULL;
    GST_OBJECT_UNLOCK (pad);
    GST_CAT_LEVEL_LOG (GST_CAT_SCHEDULING,
        (ret >= GST_FLOW_UNEXPECTED) ? GST_LEVEL_INFO : GST_LEVEL_WARNING,
        pad, "pullrange failed, flow: %s", gst_flow_get_name (ret));
    return ret;
  }
post_probe_stopped:
  {
    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
        "post probe returned %s", gst_flow_get_name (ret));
    GST_OBJECT_UNLOCK (pad);
    if (ret == GST_FLOW_OK)
      gst_buffer_unref (*buffer);
    *buffer = NULL;
    return ret;
  }
events_error:
  {
    GST_OBJECT_UNLOCK (pad);
    gst_buffer_unref (*buffer);
    *buffer = NULL;
    GST_CAT_WARNING_OBJECT (GST_CAT_SCHEDULING, pad,
        "pullrange returned events that were not accepted");
    return ret;
  }
}

/**
 * gst_pad_push_event:
 * @pad: a #GstPad to push the event to.
 * @event: (transfer full): the #GstEvent to send to the pad.
 *
 * Sends the event to the peer of the given pad. This function is
 * mainly used by elements to send events to their peer
 * elements.
 *
 * This function takes owership of the provided event so you should
 * gst_event_ref() it if you want to reuse the event after this call.
 *
 * Returns: TRUE if the event was handled.
 *
 * MT safe.
 */
gboolean
gst_pad_push_event (GstPad * pad, GstEvent * event)
{
  GstFlowReturn ret;
  GstPad *peerpad;
  gboolean result;
  gboolean stored = FALSE;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);
  g_return_val_if_fail (GST_IS_EVENT (event), FALSE);

  GST_OBJECT_LOCK (pad);

  peerpad = GST_PAD_PEER (pad);

  /* Two checks to be made:
   * . (un)set the FLUSHING flag for flushing events,
   * . handle pad blocking */
  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_FLUSH_START:
      GST_PAD_SET_FLUSHING (pad);

      if (G_UNLIKELY (GST_PAD_IS_BLOCKED (pad))) {
        /* flush start will have set the FLUSHING flag and will then
         * unlock all threads doing a GCond wait on the blocking pad. This
         * will typically unblock the STREAMING thread blocked on a pad. */
        GST_LOG_OBJECT (pad, "Pad is blocked, not forwarding flush-start, "
            "doing block signal.");
        GST_PAD_BLOCK_BROADCAST (pad);
        goto flushed;
      }
      break;
    case GST_EVENT_FLUSH_STOP:
      GST_PAD_UNSET_FLUSHING (pad);
      if (G_UNLIKELY (GST_PAD_IS_BLOCKED (pad))) {
        GST_LOG_OBJECT (pad, "Pad is blocked, not forwarding flush-stop");
        goto flushed;
      }
      break;
    default:
    {
      /* store the event on the pad, but only on srcpads */
      if (GST_PAD_IS_SRC (pad) && GST_EVENT_IS_STICKY (event)) {
        guint idx;

        idx = GST_EVENT_STICKY_IDX (event);
        GST_LOG_OBJECT (pad, "storing sticky event %s at index %u",
            GST_EVENT_TYPE_NAME (event), idx);

        /* srcpad sticky events always become active immediately */
        gst_event_replace (&pad->priv->events[idx].event, event);

        stored = TRUE;
      }

      /* backwards compatibility mode for caps */
      switch (GST_EVENT_TYPE (event)) {
        case GST_EVENT_CAPS:
        {
          GST_OBJECT_UNLOCK (pad);

          g_object_notify_by_pspec ((GObject *) pad, pspec_caps);

          GST_OBJECT_LOCK (pad);
          /* the peerpad might have changed. Things we checked above could not
           * have changed. */
          peerpad = GST_PAD_PEER (pad);
          break;
        }
        case GST_EVENT_SEGMENT:
        {
          gint64 offset;

          offset = pad->offset;
          /* check if we need to adjust the segment */
          if (offset != 0 && (peerpad != NULL)) {
            GstSegment segment;

            /* copy segment values */
            gst_event_copy_segment (event, &segment);
            gst_event_unref (event);

            /* adjust and make a new event with the offset applied */
            segment.base += offset;
            event = gst_event_new_segment (&segment);
          }
          break;
        }
        case GST_EVENT_RECONFIGURE:
          if (GST_PAD_IS_SINK (pad))
            GST_OBJECT_FLAG_SET (pad, GST_PAD_NEED_RECONFIGURE);
          break;
        default:
          break;
      }

      if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
        goto flushed;

      PROBE (pad, GST_PROBE_TYPE_PUSH | GST_PROBE_TYPE_EVENT
          | GST_PROBE_TYPE_BLOCK, event, probe_stopped);

      break;
    }
  }

  /* send probes after modifying the events above */
  PROBE (pad, GST_PROBE_TYPE_PUSH | GST_PROBE_TYPE_EVENT, event, probe_stopped);

  /* now check the peer pad */
  if (peerpad == NULL)
    goto not_linked;

  gst_object_ref (peerpad);
  pad->priv->using++;
  GST_OBJECT_UNLOCK (pad);

  GST_LOG_OBJECT (pad, "sending event %p (%s) to peerpad %" GST_PTR_FORMAT,
      event, GST_EVENT_TYPE_NAME (event), peerpad);

  result = gst_pad_send_event (peerpad, event);

  /* Note: we gave away ownership of the event at this point but we can still
   * print the old pointer */
  GST_LOG_OBJECT (pad,
      "sent event %p to peerpad %" GST_PTR_FORMAT ", result %d", event, peerpad,
      result);

  gst_object_unref (peerpad);

  GST_OBJECT_LOCK (pad);
  pad->priv->using--;
  if (pad->priv->using == 0) {
    /* pad is not active anymore, trigger idle callbacks */
    PROBE (pad, GST_PROBE_TYPE_PUSH | GST_PROBE_TYPE_IDLE, NULL, probe_stopped);
  }
  GST_OBJECT_UNLOCK (pad);

  return result | stored;

  /* ERROR handling */
flushed:
  {
    GST_DEBUG_OBJECT (pad, "We're flushing");
    GST_OBJECT_UNLOCK (pad);
    gst_event_unref (event);
    return stored;
  }
probe_stopped:
  {
    GST_DEBUG_OBJECT (pad, "Probe returned %s", gst_flow_get_name (ret));
    GST_OBJECT_UNLOCK (pad);
    gst_event_unref (event);
    return stored;
  }
not_linked:
  {
    GST_DEBUG_OBJECT (pad, "Dropping event because pad is not linked");
    GST_OBJECT_UNLOCK (pad);
    gst_event_unref (event);
    return stored;
  }
}

/**
 * gst_pad_send_event:
 * @pad: a #GstPad to send the event to.
 * @event: (transfer full): the #GstEvent to send to the pad.
 *
 * Sends the event to the pad. This function can be used
 * by applications to send events in the pipeline.
 *
 * If @pad is a source pad, @event should be an upstream event. If @pad is a
 * sink pad, @event should be a downstream event. For example, you would not
 * send a #GST_EVENT_EOS on a src pad; EOS events only propagate downstream.
 * Furthermore, some downstream events have to be serialized with data flow,
 * like EOS, while some can travel out-of-band, like #GST_EVENT_FLUSH_START. If
 * the event needs to be serialized with data flow, this function will take the
 * pad's stream lock while calling its event function.
 *
 * To find out whether an event type is upstream, downstream, or downstream and
 * serialized, see #GstEventTypeFlags, gst_event_type_get_flags(),
 * #GST_EVENT_IS_UPSTREAM, #GST_EVENT_IS_DOWNSTREAM, and
 * #GST_EVENT_IS_SERIALIZED. Note that in practice that an application or
 * plugin doesn't need to bother itself with this information; the core handles
 * all necessary locks and checks.
 *
 * This function takes owership of the provided event so you should
 * gst_event_ref() it if you want to reuse the event after this call.
 *
 * Returns: TRUE if the event was handled.
 */
gboolean
gst_pad_send_event (GstPad * pad, GstEvent * event)
{
  GstFlowReturn ret;
  gboolean result = FALSE;
  gboolean serialized, need_unlock = FALSE, needs_events, sticky;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);

  GST_OBJECT_LOCK (pad);
  if (GST_PAD_IS_SINK (pad)) {
    if (G_UNLIKELY (!GST_EVENT_IS_DOWNSTREAM (event)))
      goto wrong_direction;
    serialized = GST_EVENT_IS_SERIALIZED (event);
    sticky = GST_EVENT_IS_STICKY (event);
  } else if (GST_PAD_IS_SRC (pad)) {
    if (G_UNLIKELY (!GST_EVENT_IS_UPSTREAM (event)))
      goto wrong_direction;
    /* events on srcpad never are serialized and sticky */
    serialized = sticky = FALSE;
  } else
    goto unknown_direction;

  /* get the flag first, we clear it when we have a FLUSH or a non-serialized
   * event. */
  needs_events = GST_PAD_NEEDS_EVENTS (pad);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_FLUSH_START:
      GST_CAT_DEBUG_OBJECT (GST_CAT_EVENT, pad,
          "have event type %d (FLUSH_START)", GST_EVENT_TYPE (event));

      /* can't even accept a flush begin event when flushing */
      if (GST_PAD_IS_FLUSHING (pad))
        goto flushing;

      GST_PAD_SET_FLUSHING (pad);
      GST_CAT_DEBUG_OBJECT (GST_CAT_EVENT, pad, "set flush flag");
      needs_events = FALSE;
      break;
    case GST_EVENT_FLUSH_STOP:
      if (G_LIKELY (GST_PAD_ACTIVATE_MODE (pad) != GST_ACTIVATE_NONE)) {
        GST_PAD_UNSET_FLUSHING (pad);
        GST_CAT_DEBUG_OBJECT (GST_CAT_EVENT, pad, "cleared flush flag");
      }
      GST_OBJECT_UNLOCK (pad);
      /* grab stream lock */
      GST_PAD_STREAM_LOCK (pad);
      need_unlock = TRUE;
      GST_OBJECT_LOCK (pad);
      needs_events = FALSE;
      break;
    case GST_EVENT_RECONFIGURE:
      if (GST_PAD_IS_SRC (pad))
        GST_OBJECT_FLAG_SET (pad, GST_PAD_NEED_RECONFIGURE);
    default:
      GST_CAT_DEBUG_OBJECT (GST_CAT_EVENT, pad, "have event type %s",
          GST_EVENT_TYPE_NAME (event));

      if (serialized) {
        /* lock order: STREAM_LOCK, LOCK, recheck flushing. */
        GST_OBJECT_UNLOCK (pad);
        GST_PAD_STREAM_LOCK (pad);
        need_unlock = TRUE;
        GST_OBJECT_LOCK (pad);
      } else {
        /* don't forward events on non-serialized events */
        needs_events = FALSE;
      }

      /* store the event on the pad, but only on srcpads. We need to store the
       * event before checking the flushing flag. */
      if (sticky) {
        guint idx;
        PadEvent *ev;

        switch (GST_EVENT_TYPE (event)) {
          case GST_EVENT_SEGMENT:
            if (pad->offset != 0) {
              GstSegment segment;

              /* copy segment values */
              gst_event_copy_segment (event, &segment);
              gst_event_unref (event);

              /* adjust and make a new event with the offset applied */
              segment.base += pad->offset;
              event = gst_event_new_segment (&segment);
            }
            break;
          default:
            break;
        }

        idx = GST_EVENT_STICKY_IDX (event);
        ev = &pad->priv->events[idx];

        if (ev->event != event) {
          GST_LOG_OBJECT (pad, "storing sticky event %s at index %u",
              GST_EVENT_TYPE_NAME (event), idx);
          gst_event_replace (&ev->pending, event);
          /* set the flag so that we update the events next time. We would
           * usually update below but we might be flushing too. */
          GST_OBJECT_FLAG_SET (pad, GST_PAD_NEED_EVENTS);
          needs_events = TRUE;
        }
      }
      /* now do the probe */
      if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
        goto flushing;

      PROBE (pad, GST_PROBE_TYPE_PUSH | GST_PROBE_TYPE_EVENT, event,
          probe_stopped);

      break;
  }

  if (G_UNLIKELY (needs_events)) {
    GstFlowReturn ret;

    GST_OBJECT_FLAG_UNSET (pad, GST_PAD_NEED_EVENTS);

    GST_DEBUG_OBJECT (pad, "need to update all events");
    ret = gst_pad_update_events (pad);
    if (ret != GST_FLOW_OK)
      goto update_failed;
    GST_OBJECT_UNLOCK (pad);

    gst_event_unref (event);

    result = TRUE;
  }

  /* ensure to pass on event;
   * note that a sticky event has already been updated above */
  if (G_LIKELY (!needs_events || !sticky)) {
    GstPadEventFunction eventfunc;

    if (G_UNLIKELY ((eventfunc = GST_PAD_EVENTFUNC (pad)) == NULL))
      goto no_function;

    GST_OBJECT_UNLOCK (pad);

    result = eventfunc (pad, event);
  }

  if (need_unlock)
    GST_PAD_STREAM_UNLOCK (pad);

  GST_DEBUG_OBJECT (pad, "sent event, result %d", result);

  return result;

  /* ERROR handling */
wrong_direction:
  {
    g_warning ("pad %s:%s sending %s event in wrong direction",
        GST_DEBUG_PAD_NAME (pad), GST_EVENT_TYPE_NAME (event));
    GST_OBJECT_UNLOCK (pad);
    gst_event_unref (event);
    return FALSE;
  }
unknown_direction:
  {
    g_warning ("pad %s:%s has invalid direction", GST_DEBUG_PAD_NAME (pad));
    GST_OBJECT_UNLOCK (pad);
    gst_event_unref (event);
    return FALSE;
  }
no_function:
  {
    g_warning ("pad %s:%s has no event handler, file a bug.",
        GST_DEBUG_PAD_NAME (pad));
    GST_OBJECT_UNLOCK (pad);
    if (need_unlock)
      GST_PAD_STREAM_UNLOCK (pad);
    gst_event_unref (event);
    return FALSE;
  }
flushing:
  {
    GST_OBJECT_UNLOCK (pad);
    if (need_unlock)
      GST_PAD_STREAM_UNLOCK (pad);
    GST_CAT_INFO_OBJECT (GST_CAT_EVENT, pad,
        "Received event on flushing pad. Discarding");
    gst_event_unref (event);
    return FALSE;
  }
probe_stopped:
  {
    GST_DEBUG_OBJECT (pad, "probe returned %s", gst_flow_get_name (ret));
    GST_OBJECT_UNLOCK (pad);
    if (need_unlock)
      GST_PAD_STREAM_UNLOCK (pad);
    gst_event_unref (event);
    return FALSE;
  }
update_failed:
  {
    GST_OBJECT_UNLOCK (pad);
    if (need_unlock)
      GST_PAD_STREAM_UNLOCK (pad);
    GST_CAT_INFO_OBJECT (GST_CAT_EVENT, pad, "Update events failed");
    gst_event_unref (event);
    return FALSE;
  }
}

/**
 * gst_pad_set_element_private:
 * @pad: the #GstPad to set the private data of.
 * @priv: The private data to attach to the pad.
 *
 * Set the given private data gpointer on the pad.
 * This function can only be used by the element that owns the pad.
 * No locking is performed in this function.
 */
void
gst_pad_set_element_private (GstPad * pad, gpointer priv)
{
  pad->element_private = priv;
}

/**
 * gst_pad_get_element_private:
 * @pad: the #GstPad to get the private data of.
 *
 * Gets the private data of a pad.
 * No locking is performed in this function.
 *
 * Returns: (transfer none): a #gpointer to the private data.
 */
gpointer
gst_pad_get_element_private (GstPad * pad)
{
  return pad->element_private;
}

/**
 * gst_pad_get_sticky_event:
 * @pad: the #GstPad to get the event from.
 * @event_type: the #GstEventType that should be retrieved.
 *
 * Returns a new reference of the sticky event of type @event_type
 * from the event.
 *
 * Returns: (transfer full): a #GstEvent of type @event_type. Unref after usage.
 */
GstEvent *
gst_pad_get_sticky_event (GstPad * pad, GstEventType event_type)
{
  GstEvent *event = NULL;
  guint idx;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  g_return_val_if_fail ((event_type & GST_EVENT_TYPE_STICKY) != 0, NULL);

  idx = GST_EVENT_STICKY_IDX_TYPE (event_type);

  GST_OBJECT_LOCK (pad);
  if ((event = pad->priv->events[idx].event)) {
    gst_event_ref (event);
  }
  GST_OBJECT_UNLOCK (pad);

  return event;
}

/**
 * gst_pad_sticky_events_foreach:
 * @pad: the #GstPad that should be used for iteration.
 * @foreach_func: (scope call): the #GstPadStickyEventsForeachFunction that should be called for every event.
 * @user_data: (closure): the optional user data.
 *
 * Iterates all active sticky events on @pad and calls @foreach_func for every
 * event. If @foreach_func returns something else than GST_FLOW_OK the iteration
 * is immediately stopped.
 *
 * Returns: GST_FLOW_OK if iteration was successful
 */
GstFlowReturn
gst_pad_sticky_events_foreach (GstPad * pad,
    GstPadStickyEventsForeachFunction foreach_func, gpointer user_data)
{
  GstFlowReturn ret = GST_FLOW_OK;
  guint i;
  GstEvent *event;

  g_return_val_if_fail (GST_IS_PAD (pad), GST_FLOW_ERROR);
  g_return_val_if_fail (foreach_func != NULL, GST_FLOW_ERROR);

  GST_OBJECT_LOCK (pad);

restart:
  for (i = 0; i < GST_EVENT_MAX_STICKY; i++) {
    gboolean res;
    PadEvent *ev;

    ev = &pad->priv->events[i];

    /* skip without active event */
    if ((event = ev->event) == NULL)
      continue;

    gst_event_ref (event);
    GST_OBJECT_UNLOCK (pad);

    res = foreach_func (pad, event, user_data);

    GST_OBJECT_LOCK (pad);
    gst_event_unref (event);

    if (res != GST_FLOW_OK) {
      ret = res;
      break;
    }

    /* things could have changed while we release the lock, check if we still
     * are handling the same event, if we don't something changed and we have
     * to try again. FIXME. we need a cookie here. */
    if (event != ev->event) {
      GST_DEBUG_OBJECT (pad, "events changed, restarting");
      goto restart;
    }
  }
  GST_OBJECT_UNLOCK (pad);

  return ret;
}

static void
do_stream_status (GstPad * pad, GstStreamStatusType type,
    GThread * thread, GstTask * task)
{
  GstElement *parent;

  GST_DEBUG_OBJECT (pad, "doing stream-status %d", type);

  if ((parent = GST_ELEMENT_CAST (gst_pad_get_parent (pad)))) {
    if (GST_IS_ELEMENT (parent)) {
      GstMessage *message;
      GValue value = { 0 };

      if (type == GST_STREAM_STATUS_TYPE_ENTER) {
        gchar *tname, *ename, *pname;

        /* create a good task name */
        ename = gst_element_get_name (parent);
        pname = gst_pad_get_name (pad);
        tname = g_strdup_printf ("%s:%s", ename, pname);
        g_free (ename);
        g_free (pname);

        gst_object_set_name (GST_OBJECT_CAST (task), tname);
        g_free (tname);
      }

      message = gst_message_new_stream_status (GST_OBJECT_CAST (pad),
          type, parent);

      g_value_init (&value, GST_TYPE_TASK);
      g_value_set_object (&value, task);
      gst_message_set_stream_status_object (message, &value);
      g_value_unset (&value);

      GST_DEBUG_OBJECT (pad, "posting stream-status %d", type);
      gst_element_post_message (parent, message);
    }
    gst_object_unref (parent);
  }
}

static void
pad_enter_thread (GstTask * task, GThread * thread, gpointer user_data)
{
  do_stream_status (GST_PAD_CAST (user_data), GST_STREAM_STATUS_TYPE_ENTER,
      thread, task);
}

static void
pad_leave_thread (GstTask * task, GThread * thread, gpointer user_data)
{
  do_stream_status (GST_PAD_CAST (user_data), GST_STREAM_STATUS_TYPE_LEAVE,
      thread, task);
}

static GstTaskThreadCallbacks thr_callbacks = {
  pad_enter_thread,
  pad_leave_thread,
};

/**
 * gst_pad_start_task:
 * @pad: the #GstPad to start the task of
 * @func: the task function to call
 * @data: data passed to the task function
 *
 * Starts a task that repeatedly calls @func with @data. This function
 * is mostly used in pad activation functions to start the dataflow.
 * The #GST_PAD_STREAM_LOCK of @pad will automatically be acquired
 * before @func is called.
 *
 * Returns: a %TRUE if the task could be started.
 */
gboolean
gst_pad_start_task (GstPad * pad, GstTaskFunction func, gpointer data)
{
  GstTask *task;
  gboolean res;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (func != NULL, FALSE);

  GST_DEBUG_OBJECT (pad, "start task");

  GST_OBJECT_LOCK (pad);
  task = GST_PAD_TASK (pad);
  if (task == NULL) {
    task = gst_task_create (func, data);
    gst_task_set_lock (task, GST_PAD_GET_STREAM_LOCK (pad));
    gst_task_set_thread_callbacks (task, &thr_callbacks, pad, NULL);
    GST_DEBUG_OBJECT (pad, "created task");
    GST_PAD_TASK (pad) = task;
    gst_object_ref (task);
    /* release lock to post the message */
    GST_OBJECT_UNLOCK (pad);

    do_stream_status (pad, GST_STREAM_STATUS_TYPE_CREATE, NULL, task);

    gst_object_unref (task);

    GST_OBJECT_LOCK (pad);
    /* nobody else is supposed to have changed the pad now */
    if (GST_PAD_TASK (pad) != task)
      goto concurrent_stop;
  }
  res = gst_task_set_state (task, GST_TASK_STARTED);
  GST_OBJECT_UNLOCK (pad);

  return res;

  /* ERRORS */
concurrent_stop:
  {
    GST_OBJECT_UNLOCK (pad);
    return TRUE;
  }
}

/**
 * gst_pad_pause_task:
 * @pad: the #GstPad to pause the task of
 *
 * Pause the task of @pad. This function will also wait until the
 * function executed by the task is finished if this function is not
 * called from the task function.
 *
 * Returns: a TRUE if the task could be paused or FALSE when the pad
 * has no task.
 */
gboolean
gst_pad_pause_task (GstPad * pad)
{
  GstTask *task;
  gboolean res;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_DEBUG_OBJECT (pad, "pause task");

  GST_OBJECT_LOCK (pad);
  task = GST_PAD_TASK (pad);
  if (task == NULL)
    goto no_task;
  res = gst_task_set_state (task, GST_TASK_PAUSED);
  GST_OBJECT_UNLOCK (pad);

  /* wait for task function to finish, this lock is recursive so it does nothing
   * when the pause is called from the task itself */
  GST_PAD_STREAM_LOCK (pad);
  GST_PAD_STREAM_UNLOCK (pad);

  return res;

no_task:
  {
    GST_DEBUG_OBJECT (pad, "pad has no task");
    GST_OBJECT_UNLOCK (pad);
    return FALSE;
  }
}

/**
 * gst_pad_stop_task:
 * @pad: the #GstPad to stop the task of
 *
 * Stop the task of @pad. This function will also make sure that the
 * function executed by the task will effectively stop if not called
 * from the GstTaskFunction.
 *
 * This function will deadlock if called from the GstTaskFunction of
 * the task. Use gst_task_pause() instead.
 *
 * Regardless of whether the pad has a task, the stream lock is acquired and
 * released so as to ensure that streaming through this pad has finished.
 *
 * Returns: a TRUE if the task could be stopped or FALSE on error.
 */
gboolean
gst_pad_stop_task (GstPad * pad)
{
  GstTask *task;
  gboolean res;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_DEBUG_OBJECT (pad, "stop task");

  GST_OBJECT_LOCK (pad);
  task = GST_PAD_TASK (pad);
  if (task == NULL)
    goto no_task;
  GST_PAD_TASK (pad) = NULL;
  res = gst_task_set_state (task, GST_TASK_STOPPED);
  GST_OBJECT_UNLOCK (pad);

  GST_PAD_STREAM_LOCK (pad);
  GST_PAD_STREAM_UNLOCK (pad);

  if (!gst_task_join (task))
    goto join_failed;

  gst_object_unref (task);

  return res;

no_task:
  {
    GST_DEBUG_OBJECT (pad, "no task");
    GST_OBJECT_UNLOCK (pad);

    GST_PAD_STREAM_LOCK (pad);
    GST_PAD_STREAM_UNLOCK (pad);

    /* this is not an error */
    return TRUE;
  }
join_failed:
  {
    /* this is bad, possibly the application tried to join the task from
     * the task's thread. We install the task again so that it will be stopped
     * again from the right thread next time hopefully. */
    GST_OBJECT_LOCK (pad);
    GST_DEBUG_OBJECT (pad, "join failed");
    /* we can only install this task if there was no other task */
    if (GST_PAD_TASK (pad) == NULL)
      GST_PAD_TASK (pad) = task;
    GST_OBJECT_UNLOCK (pad);

    return FALSE;
  }
}