gstreamer/libs/gst/base/gstcollectpads.c

/* GStreamer
 * Copyright (C) 2005 Wim Taymans <wim@fluendo.com>
 *
 * gstcollectpads.c:
 *
 * 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:gstcollectpads
 * @short_description: manages a set of pads that operate in collect mode
 * @see_also:
 *
 * Manages a set of pads that operate in collect mode. This means that control
 * is given to the manager of this object when all pads have data.
 * <itemizedlist>
 *   <listitem><para>
 *     Collectpads are created with gst_collect_pads_new(). A callback should then
 *     be installed with gst_collect_pads_set_function (). 
 *   </para></listitem>
 *   <listitem><para>
 *     Pads are added to the collection with gst_collect_pads_add_pad()/
 *     gst_collect_pads_remove_pad(). The pad
 *     has to be a sinkpad. The chain and event functions of the pad are
 *     overridden. The element_private of the pad is used to store
 *     private information for the collectpads.
 *   </para></listitem>
 *   <listitem><para>
 *     For each pad, data is queued in the _chain function or by
 *     performing a pull_range.
 *   </para></listitem>
 *   <listitem><para>
 *     When data is queued on all pads, the callback function is called.
 *   </para></listitem>
 *   <listitem><para>
 *     Data can be dequeued from the pad with the gst_collect_pads_pop() method.
 *     One can peek at the data with the gst_collect_pads_peek() function.
 *     These functions will return NULL if the pad received an EOS event. When all
 *     pads return NULL from a gst_collect_pads_peek(), the element can emit an EOS
 *     event itself.
 *   </para></listitem>
 *   <listitem><para>
 *     Data can also be dequeued in byte units using the gst_collect_pads_available(), 
 *     gst_collect_pads_read() and gst_collect_pads_flush() calls.
 *   </para></listitem>
 *   <listitem><para>
 *     Elements should call gst_collect_pads_start() and gst_collect_pads_stop() in
 *     their state change functions to start and stop the processing of the collecpads.
 *     The gst_collect_pads_stop() call should be called before calling the parent
 *     element state change function in the PAUSED_TO_READY state change to ensure
 *     no pad is blocked and the element can finish streaming.
 *   </para></listitem>
 *   <listitem><para>
 *     gst_collect_pads_collect() and gst_collect_pads_collect_range() can be used by
 *     elements that start a #GstTask to drive the collect_pads. This feature is however
 *     not yet implemented.
 *   </para></listitem>
 * </itemizedlist>
 *
 * Last reviewed on 2006-05-10 (0.10.6)
 */

#include "gstcollectpads.h"

GST_DEBUG_CATEGORY_STATIC (collect_pads_debug);
#define GST_CAT_DEFAULT collect_pads_debug

GST_BOILERPLATE (GstCollectPads, gst_collect_pads, GstObject, GST_TYPE_OBJECT);

static GstFlowReturn gst_collect_pads_chain (GstPad * pad, GstBuffer * buffer);
static gboolean gst_collect_pads_event (GstPad * pad, GstEvent * event);
static void gst_collect_pads_finalize (GObject * object);
static void gst_collect_pads_init (GstCollectPads * pads,
    GstCollectPadsClass * g_class);

static void
gst_collect_pads_base_init (gpointer g_class)
{
  GST_DEBUG_CATEGORY_INIT (collect_pads_debug, "collectpads", 0,
      "GstCollectPads");
}

static void
gst_collect_pads_class_init (GstCollectPadsClass * klass)
{
  GObjectClass *gobject_class = (GObjectClass *) klass;

  gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_collect_pads_finalize);
}

static void
gst_collect_pads_init (GstCollectPads * pads, GstCollectPadsClass * g_class)
{
  pads->cond = g_cond_new ();
  pads->data = NULL;
  pads->cookie = 0;
  pads->numpads = 0;
  pads->queuedpads = 0;
  pads->eospads = 0;
  pads->started = FALSE;

  /* members to manage the pad list */
  pads->abidata.ABI.pad_lock = g_mutex_new ();
  pads->abidata.ABI.pad_cookie = 0;
  pads->abidata.ABI.pad_list = NULL;
}

static void
gst_collect_pads_finalize (GObject * object)
{
  GSList *collected;
  GstCollectPads *pads = GST_COLLECT_PADS (object);

  GST_DEBUG ("finalize");

  g_cond_free (pads->cond);
  g_mutex_free (pads->abidata.ABI.pad_lock);

  /* Remove pads */
  collected = pads->abidata.ABI.pad_list;
  for (; collected; collected = g_slist_next (collected)) {
    GstCollectData *pdata = (GstCollectData *) collected->data;

    if (pdata->pad) {
      GST_DEBUG ("finalize pad %s:%s", GST_DEBUG_PAD_NAME (pdata->pad));
      gst_object_unref (pdata->pad);
      pdata->pad = NULL;
    }
    g_free (pdata);
  }
  /* Free pads list */
  g_slist_free (pads->data);
  g_slist_free (pads->abidata.ABI.pad_list);

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

/**
 * gst_collect_pads_new:
 *
 * Create a new instance of #GstCollectsPads.
 *
 * Returns: a new #GstCollectPads, or NULL in case of an error.
 *
 * MT safe.
 */
GstCollectPads *
gst_collect_pads_new (void)
{
  GstCollectPads *newcoll;

  newcoll = g_object_new (GST_TYPE_COLLECT_PADS, NULL);

  return newcoll;
}

/**
 * gst_collect_pads_set_function:
 * @pads: the collectspads to use
 * @func: the function to set
 * @user_data: user data passed to the function
 *
 * Set the callback function and user data that will be called when
 * all the pads added to the collection have buffers queued.
 *
 * MT safe.
 */
void
gst_collect_pads_set_function (GstCollectPads * pads,
    GstCollectPadsFunction func, gpointer user_data)
{
  g_return_if_fail (pads != NULL);
  g_return_if_fail (GST_IS_COLLECT_PADS (pads));

  GST_OBJECT_LOCK (pads);
  pads->func = func;
  pads->user_data = user_data;
  GST_OBJECT_UNLOCK (pads);
}

/**
 * gst_collect_pads_add_pad:
 * @pads: the collectspads to use
 * @pad: the pad to add
 * @size: the size of the returned GstCollectData structure
 *
 * Add a pad to the collection of collect pads. The pad has to be
 * a sinkpad.
 *
 * You specify a size for the returned #GstCollectData structure
 * so that you can use it to store additional information.
 *
 * Returns: a new #GstCollectData to identify the new pad. Or NULL
 *   if wrong parameters are supplied.
 *
 * MT safe.
 */
GstCollectData *
gst_collect_pads_add_pad (GstCollectPads * pads, GstPad * pad, guint size)
{
  GstCollectData *data;

  g_return_val_if_fail (pads != NULL, NULL);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), NULL);
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_PAD_IS_SINK (pad), NULL);
  g_return_val_if_fail (size >= sizeof (GstCollectData), NULL);

  GST_DEBUG ("adding pad %s:%s", GST_DEBUG_PAD_NAME (pad));

  data = g_malloc0 (size);
  data->collect = pads;
  data->pad = gst_object_ref (pad);
  data->buffer = NULL;
  data->pos = 0;
  gst_segment_init (&data->segment, GST_FORMAT_UNDEFINED);
  data->abidata.ABI.flushing = FALSE;
  data->abidata.ABI.new_segment = FALSE;
  data->abidata.ABI.eos = FALSE;

  GST_COLLECT_PADS_PAD_LOCK (pads);
  pads->abidata.ABI.pad_list =
      g_slist_append (pads->abidata.ABI.pad_list, data);
  gst_pad_set_chain_function (pad, GST_DEBUG_FUNCPTR (gst_collect_pads_chain));
  gst_pad_set_event_function (pad, GST_DEBUG_FUNCPTR (gst_collect_pads_event));
  gst_pad_set_element_private (pad, data);
  pads->abidata.ABI.pad_cookie++;
  GST_COLLECT_PADS_PAD_UNLOCK (pads);

  return data;
}

static gint
find_pad (GstCollectData * data, GstPad * pad)
{
  if (data->pad == pad)
    return 0;
  return 1;
}

/**
 * gst_collect_pads_remove_pad:
 * @pads: the collectspads to use
 * @pad: the pad to remove
 *
 * Remove a pad from the collection of collect pads.
 *
 * Returns: TRUE if the pad could be removed.
 *
 * MT safe.
 */
gboolean
gst_collect_pads_remove_pad (GstCollectPads * pads, GstPad * pad)
{
  GSList *list;

  g_return_val_if_fail (pads != NULL, FALSE);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), FALSE);
  g_return_val_if_fail (pad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_DEBUG ("removing pad %s:%s", GST_DEBUG_PAD_NAME (pad));

  GST_COLLECT_PADS_PAD_LOCK (pads);
  list =
      g_slist_find_custom (pads->abidata.ABI.pad_list, pad,
      (GCompareFunc) find_pad);
  if (!list)
    goto unknown_pad;

  GST_DEBUG ("found pad %s:%s at %p", GST_DEBUG_PAD_NAME (pad), list->data);
  /* clear the stuff we configured */
  gst_pad_set_chain_function (pad, NULL);
  gst_pad_set_event_function (pad, NULL);
  /* FIXME, check that freeing the private data does not causes
   * crashes in the streaming thread */
  gst_pad_set_element_private (pad, NULL);

  /* backward compat, also remove from data if stopped */
  if (!pads->started) {
    GSList *dlist;

    dlist = g_slist_find_custom (pads->data, pad, (GCompareFunc) find_pad);
    if (dlist) {
      pads->data = g_slist_delete_link (pads->data, dlist);
    }
  }
  gst_object_unref (pad);
  g_free (list->data);
  pads->abidata.ABI.pad_list =
      g_slist_delete_link (pads->abidata.ABI.pad_list, list);
  pads->abidata.ABI.pad_cookie++;
  GST_COLLECT_PADS_PAD_UNLOCK (pads);

  return TRUE;

unknown_pad:
  {
    GST_WARNING ("cannot remove unknown pad %s:%s", GST_DEBUG_PAD_NAME (pad));
    return FALSE;
  }
}

/**
 * gst_collect_pads_is_active:
 * @pads: the collectspads to use
 * @pad: the pad to check
 *
 * Check if a pad is active.
 *
 * This function is currently not implemented.
 *
 * Returns: TRUE if the pad is active.
 *
 * MT safe.
 */
gboolean
gst_collect_pads_is_active (GstCollectPads * pads, GstPad * pad)
{
  g_return_val_if_fail (pads != NULL, FALSE);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), FALSE);
  g_return_val_if_fail (pad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  g_warning ("gst_collect_pads_is_active() is not implemented");

  return FALSE;
}

/**
 * gst_collect_pads_collect:
 * @pads: the collectspads to use
 *
 * Collect data on all pads. This function is usually called
 * from a GstTask function in an element. 
 *
 * This function is currently not implemented.
 *
 * Returns: GstFlowReturn of the operation.
 *
 * MT safe.
 */
GstFlowReturn
gst_collect_pads_collect (GstCollectPads * pads)
{
  g_return_val_if_fail (pads != NULL, GST_FLOW_ERROR);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), GST_FLOW_ERROR);

  g_warning ("gst_collect_pads_collect() is not implemented");

  return GST_FLOW_NOT_SUPPORTED;
}

/**
 * gst_collect_pads_collect_range:
 * @pads: the collectspads to use
 * @offset: the offset to collect
 * @length: the length to collect
 *
 * Collect data with @offset and @length on all pads. This function
 * is typically called in the getrange function of an element. 
 *
 * This function is currently not implemented.
 *
 * Returns: GstFlowReturn of the operation.
 *
 * MT safe.
 */
GstFlowReturn
gst_collect_pads_collect_range (GstCollectPads * pads, guint64 offset,
    guint length)
{
  g_return_val_if_fail (pads != NULL, GST_FLOW_ERROR);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), GST_FLOW_ERROR);

  g_warning ("gst_collect_pads_collect_range() is not implemented");

  return GST_FLOW_NOT_SUPPORTED;
}

/* FIXME, I think this function is used to work around bad behaviour
 * of elements that add pads to themselves without activating them.
 *
 * Must be called with PAD_LOCK.
 */
static void
gst_collect_pads_set_flushing_unlocked (GstCollectPads * pads,
    gboolean flushing)
{
  GSList *walk = NULL;

  /* Update the pads flushing flag */
  for (walk = pads->data; walk; walk = g_slist_next (walk)) {
    GstCollectData *cdata = walk->data;

    if (GST_IS_PAD (cdata->pad)) {
      GST_OBJECT_LOCK (cdata->pad);
      if (flushing)
        GST_PAD_SET_FLUSHING (cdata->pad);
      else
        GST_PAD_UNSET_FLUSHING (cdata->pad);
      cdata->abidata.ABI.flushing = flushing;
      GST_OBJECT_UNLOCK (cdata->pad);
    }
  }
}

/**
 * gst_collect_pads_set_flushing:
 * @pads: the collectspads to use
 * @flushing: desired state of the pads
 *
 * Change the flushing state of all the pads in the collection. No pad
 * is able to accept anymore data when @flushing is %TRUE. Calling this
 * function with @flushing %TRUE makes @pads accept data again.
 *
 * MT safe.
 *
 * Since: 0.10.7.
 */
void
gst_collect_pads_set_flushing (GstCollectPads * pads, gboolean flushing)
{
  g_return_if_fail (pads != NULL);
  g_return_if_fail (GST_IS_COLLECT_PADS (pads));

  GST_COLLECT_PADS_PAD_LOCK (pads);
  gst_collect_pads_set_flushing_unlocked (pads, flushing);
  GST_COLLECT_PADS_PAD_UNLOCK (pads);
}

/**
 * gst_collect_pads_start:
 * @pads: the collectspads to use
 *
 * Starts the processing of data in the collect_pads.
 *
 * MT safe.
 */
void
gst_collect_pads_start (GstCollectPads * pads)
{
  GSList *collected;

  g_return_if_fail (pads != NULL);
  g_return_if_fail (GST_IS_COLLECT_PADS (pads));

  GST_DEBUG_OBJECT (pads, "starting collect pads");

  /* make sure stop and collect cannot be called anymore */
  GST_OBJECT_LOCK (pads);

  /* make pads streamable */
  GST_COLLECT_PADS_PAD_LOCK (pads);

  /* loop over the master pad list and reset the segment */
  collected = pads->abidata.ABI.pad_list;
  for (; collected; collected = g_slist_next (collected)) {
    GstCollectData *data;

    data = collected->data;
    gst_segment_init (&data->segment, GST_FORMAT_UNDEFINED);
  }

  gst_collect_pads_set_flushing_unlocked (pads, FALSE);

  /* Start collect pads */
  pads->started = TRUE;
  GST_COLLECT_PADS_PAD_UNLOCK (pads);
  GST_OBJECT_UNLOCK (pads);
}

/**
 * gst_collect_pads_stop:
 * @pads: the collectspads to use
 *
 * Stops the processing of data in the collect_pads. this function
 * will also unblock any blocking operations.
 *
 * MT safe.
 */
void
gst_collect_pads_stop (GstCollectPads * pads)
{
  GSList *collected;

  g_return_if_fail (pads != NULL);
  g_return_if_fail (GST_IS_COLLECT_PADS (pads));

  GST_DEBUG_OBJECT (pads, "stopping collect pads");

  /* make sure collect and start cannot be called anymore */
  GST_OBJECT_LOCK (pads);

  /* make pads not accept data anymore */
  GST_COLLECT_PADS_PAD_LOCK (pads);
  gst_collect_pads_set_flushing_unlocked (pads, TRUE);

  /* Stop collect pads */
  pads->started = FALSE;

  /* loop over the master pad list and flush buffers */
  collected = pads->abidata.ABI.pad_list;
  for (; collected; collected = g_slist_next (collected)) {
    GstCollectData *data;
    GstBuffer **buffer_p;

    data = collected->data;
    if (data->buffer) {
      buffer_p = &data->buffer;
      gst_buffer_replace (buffer_p, NULL);
      data->pos = 0;
      /* one less pad with queued data now */
      pads->queuedpads--;
    }
  }

  GST_COLLECT_PADS_PAD_UNLOCK (pads);
  /* Wake them up so then can end the chain functions. */
  GST_COLLECT_PADS_BROADCAST (pads);

  GST_OBJECT_UNLOCK (pads);
}

/**
 * gst_collect_pads_peek:
 * @pads: the collectspads to peek
 * @data: the data to use
 *
 * Peek at the buffer currently queued in @data. This function
 * should be called with the @pads LOCK held, such as in the callback
 * handler.
 *
 * Returns: The buffer in @data or NULL if no buffer is queued.
 *  should unref the buffer after usage.
 *
 * MT safe.
 */
GstBuffer *
gst_collect_pads_peek (GstCollectPads * pads, GstCollectData * data)
{
  GstBuffer *result;

  g_return_val_if_fail (pads != NULL, NULL);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), NULL);
  g_return_val_if_fail (data != NULL, NULL);

  if ((result = data->buffer))
    gst_buffer_ref (result);

  GST_DEBUG ("Peeking at pad %s:%s: buffer=%p",
      GST_DEBUG_PAD_NAME (data->pad), result);

  return result;
}

/**
 * gst_collect_pads_pop:
 * @pads: the collectspads to pop
 * @data: the data to use
 *
 * Pop the buffer currently queued in @data. This function
 * should be called with the @pads LOCK held, such as in the callback
 * handler.
 *
 * Returns: The buffer in @data or NULL if no buffer was queued.
 *   You should unref the buffer after usage.
 *
 * MT safe.
 */
GstBuffer *
gst_collect_pads_pop (GstCollectPads * pads, GstCollectData * data)
{
  GstBuffer *result;
  GstBuffer **buffer_p;

  g_return_val_if_fail (pads != NULL, NULL);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), NULL);
  g_return_val_if_fail (data != NULL, NULL);

  if ((result = data->buffer)) {
    buffer_p = &data->buffer;
    gst_buffer_replace (buffer_p, NULL);
    data->pos = 0;
    /* one less pad with queued data now */
    pads->queuedpads--;
  }

  GST_COLLECT_PADS_BROADCAST (pads);

  GST_DEBUG ("Pop buffer on pad %s:%s: buffer=%p",
      GST_DEBUG_PAD_NAME (data->pad), result);

  return result;
}

/**
 * gst_collect_pads_available:
 * @pads: the collectspads to query
 *
 * Query how much bytes can be read from each queued buffer. This means
 * that the result of this call is the maximum number of bytes that can
 * be read from each of the pads.
 *
 * This function should be called with @pads LOCK held, such as
 * in the callback.
 *
 * Returns: The maximum number of bytes queued on all pad. This function
 * returns 0 if a pad has no queued buffer.
 *
 * MT safe.
 */
/* FIXME, we can do this in the _chain functions */
guint
gst_collect_pads_available (GstCollectPads * pads)
{
  GSList *collected;
  guint result = G_MAXUINT;

  g_return_val_if_fail (pads != NULL, 0);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), 0);

  for (collected = pads->data; collected; collected = g_slist_next (collected)) {
    GstCollectData *pdata;
    GstBuffer *buffer;
    gint size;

    pdata = (GstCollectData *) collected->data;

    /* ignore pad with EOS */
    if (G_UNLIKELY (pdata->abidata.ABI.eos)) {
      GST_DEBUG ("pad %p is EOS", pdata);
      continue;
    }

    /* an empty buffer without EOS is weird when we get here.. */
    if (G_UNLIKELY ((buffer = pdata->buffer) == NULL)) {
      GST_WARNING ("pad %p has no buffer", pdata);
      goto not_filled;
    }

    /* this is the size left of the buffer */
    size = GST_BUFFER_SIZE (buffer) - pdata->pos;
    GST_DEBUG ("pad %p has %d bytes left", pdata, size);

    /* need to return the min of all available data */
    if (size < result)
      result = size;
  }
  /* nothing changed, all must be EOS then, return 0 */
  if (G_UNLIKELY (result == G_MAXUINT))
    result = 0;

  return result;

not_filled:
  {
    return 0;
  }
}

/**
 * gst_collect_pads_read:
 * @pads: the collectspads to query
 * @data: the data to use
 * @bytes: a pointer to a byte array
 * @size: the number of bytes to read
 *
 * Get a pointer in @bytes where @size bytes can be read from the
 * given pad data.
 *
 * This function should be called with @pads LOCK held, such as
 * in the callback.
 *
 * Returns: The number of bytes available for consumption in the
 * memory pointed to by @bytes. This can be less than @size and
 * is 0 if the pad is end-of-stream.
 *
 * MT safe.
 */
guint
gst_collect_pads_read (GstCollectPads * pads, GstCollectData * data,
    guint8 ** bytes, guint size)
{
  guint readsize;
  GstBuffer *buffer;

  g_return_val_if_fail (pads != NULL, 0);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), 0);
  g_return_val_if_fail (data != NULL, 0);
  g_return_val_if_fail (bytes != NULL, 0);

  /* no buffer, must be EOS */
  if ((buffer = data->buffer) == NULL)
    return 0;

  readsize = MIN (size, GST_BUFFER_SIZE (buffer) - data->pos);

  *bytes = GST_BUFFER_DATA (buffer) + data->pos;

  return readsize;
}

/**
 * gst_collect_pads_flush:
 * @pads: the collectspads to query
 * @data: the data to use
 * @size: the number of bytes to flush
 *
 * Flush @size bytes from the pad @data.
 *
 * This function should be called with @pads LOCK held, such as
 * in the callback.
 *
 * Returns: The number of bytes flushed This can be less than @size and
 * is 0 if the pad was end-of-stream.
 *
 * MT safe.
 */
guint
gst_collect_pads_flush (GstCollectPads * pads, GstCollectData * data,
    guint size)
{
  guint flushsize;
  GstBuffer *buffer;

  g_return_val_if_fail (pads != NULL, 0);
  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), 0);
  g_return_val_if_fail (data != NULL, 0);

  /* no buffer, must be EOS */
  if ((buffer = data->buffer) == NULL)
    return 0;

  /* this is what we can flush at max */
  flushsize = MIN (size, GST_BUFFER_SIZE (buffer) - data->pos);

  data->pos += size;

  if (data->pos >= GST_BUFFER_SIZE (buffer)) {
    GstBuffer *buf;

    /* _pop will also reset data->pos to 0 */
    buf = gst_collect_pads_pop (pads, data);
    gst_buffer_unref (buf);
  }

  return flushsize;
}

/* see if pads were added or removed and update our stats. Any pad
 * added after releasing the PAD_LOCK will get collected in the next
 * round.
 *
 * We can do a quick check by checking the cookies, that get changed
 * whenever the pad list is updated.
 *
 * Must be called with LOCK.
 */
static void
gst_collect_pads_check_pads (GstCollectPads * pads)
{
  /* the master list and cookie are protected with the PAD_LOCK */
  GST_COLLECT_PADS_PAD_LOCK (pads);
  if (G_UNLIKELY (pads->abidata.ABI.pad_cookie != pads->cookie)) {
    GSList *collected;

    /* clear list and stats */
    pads->data = NULL;
    pads->numpads = 0;
    pads->queuedpads = 0;
    pads->eospads = 0;

    /* loop over the master pad list */
    collected = pads->abidata.ABI.pad_list;
    for (; collected; collected = g_slist_next (collected)) {
      GstCollectData *data;

      /* update the stats */
      pads->numpads++;
      data = collected->data;
      if (data->buffer)
        pads->queuedpads++;
      if (data->abidata.ABI.eos)
        pads->eospads++;

      /* add to the list of pads to collect */
      pads->data = g_slist_prepend (pads->data, data);
    }
    /* and update the cookie */
    pads->cookie = pads->abidata.ABI.pad_cookie;
  }
  GST_COLLECT_PADS_PAD_UNLOCK (pads);
}

/* checks if all the pads are collected and call the collectfunction
 *
 * Should be called with LOCK.
 *
 * Returns: The GstFlowReturn of collection.
 */
static GstFlowReturn
gst_collect_pads_check_collected (GstCollectPads * pads)
{
  GstFlowReturn flow_ret = GST_FLOW_OK;

  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), GST_FLOW_ERROR);
  g_return_val_if_fail (pads->func != NULL, GST_FLOW_NOT_SUPPORTED);

  /* check for new pads, update stats etc.. */
  gst_collect_pads_check_pads (pads);

  if (G_UNLIKELY (pads->eospads == pads->numpads)) {
    /* If all our pads are EOS just collect once to let the element
     * do its final EOS handling. */
    GST_DEBUG ("All active pads (%d) are EOS, calling %s",
        pads->numpads, GST_DEBUG_FUNCPTR_NAME (pads->func));
    flow_ret = pads->func (pads, pads->user_data);
  } else {
    gboolean collected = FALSE;

    /* We call the collected function as long as our condition matches.
     * FIXME: should we error out if the collect function did not pop anything ?
     * we can get a busy loop here if the element does not pop from the collect
     * function
     */
    while (((pads->queuedpads + pads->eospads) >= pads->numpads)) {
      GST_DEBUG ("All active pads (%d + %d >= %d) have data, calling %s",
          pads->queuedpads, pads->eospads, pads->numpads,
          GST_DEBUG_FUNCPTR_NAME (pads->func));
      flow_ret = pads->func (pads, pads->user_data);
      collected = TRUE;

      /* break on error */
      if (flow_ret != GST_FLOW_OK)
        break;
      /* Don't keep looping after telling the element EOS or flushing */
      if (pads->queuedpads == 0)
        break;
    }
    if (!collected)
      GST_DEBUG ("Not all active pads (%d) have data, continuing",
          pads->numpads);
  }
  return flow_ret;
}

static gboolean
gst_collect_pads_event (GstPad * pad, GstEvent * event)
{
  gboolean res;
  GstCollectData *data;
  GstCollectPads *pads;

  /* some magic to get the managing collect_pads */
  data = (GstCollectData *) gst_pad_get_element_private (pad);
  if (G_UNLIKELY (data == NULL))
    goto not_ours;

  res = TRUE;

  pads = data->collect;

  GST_DEBUG ("Got %s event on pad %s:%s", GST_EVENT_TYPE_NAME (event),
      GST_DEBUG_PAD_NAME (data->pad));

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_FLUSH_START:
    {
      /* forward event to unblock check_collected */
      gst_pad_event_default (pad, event);

      /* now unblock the chain function.
       * no cond per pad, so they all unblock, 
       * non-flushing block again */
      GST_OBJECT_LOCK (pads);
      data->abidata.ABI.flushing = TRUE;
      GST_COLLECT_PADS_BROADCAST (pads);
      GST_OBJECT_UNLOCK (pads);

      /* event already cleaned up by forwarding */
      goto done;
    }
    case GST_EVENT_FLUSH_STOP:
    {
      /* flush the 1 buffer queue */
      GST_OBJECT_LOCK (pads);
      data->abidata.ABI.flushing = FALSE;
      gst_collect_pads_pop (pads, data);
      /* we need new segment info after the flush */
      gst_segment_init (&data->segment, GST_FORMAT_UNDEFINED);
      data->abidata.ABI.new_segment = FALSE;
      /* if the pad was EOS, remove the EOS flag and
       * decrement the number of eospads */
      if (G_UNLIKELY (data->abidata.ABI.eos == TRUE)) {
        pads->eospads--;
        data->abidata.ABI.eos = FALSE;
      }
      GST_OBJECT_UNLOCK (pads);

      /* forward event */
      goto forward;
    }
    case GST_EVENT_EOS:
    {
      GST_OBJECT_LOCK (pads);
      /* if the pad was not EOS, make it EOS and so we
       * have one more eospad */
      if (G_LIKELY (data->abidata.ABI.eos == FALSE)) {
        data->abidata.ABI.eos = TRUE;
        pads->eospads++;
      }
      /* check if we need collecting anything, we ignore the
       * result. */
      gst_collect_pads_check_collected (pads);
      GST_OBJECT_UNLOCK (pads);

      /* We eat this event, element should do something
       * in the collected callback. */
      gst_event_unref (event);
      goto done;
    }
    case GST_EVENT_NEWSEGMENT:
    {
      gint64 start, stop, time;
      gdouble rate, arate;
      GstFormat format;
      gboolean update;

      gst_event_parse_new_segment_full (event, &update, &rate, &arate, &format,
          &start, &stop, &time);

      GST_DEBUG_OBJECT (data->pad, "got newsegment, start %" GST_TIME_FORMAT
          ", stop %" GST_TIME_FORMAT, GST_TIME_ARGS (start),
          GST_TIME_ARGS (stop));

      if (data->segment.format != format)
        gst_segment_init (&data->segment, format);

      gst_segment_set_newsegment_full (&data->segment, update, rate, arate,
          format, start, stop, time);

      data->abidata.ABI.new_segment = TRUE;

      /* we must not forward this event since multiple segments will be 
       * accumulated and this is certainly not what we want. */
      gst_event_unref (event);
      /* FIXME: collect-pads based elements need to create their own newsegment
         event (and only one really)
         (a) make the segment part of the GstCollectData structure of each pad,
         so you can just check that once you have a buffer queued on that pad,
         (b) you can override a pad's event function with your own,
         catch the newsegment event and then pass it on to the original
         gstcollectpads event function
         (that's what avimux does for something IIRC)
         see #340060
       */
      goto done;
    }
    default:
      /* forward other events */
      goto forward;
  }

forward:
  res = gst_pad_event_default (pad, event);

done:
  return res;

  /* ERRORS */
not_ours:
  {
    GST_WARNING ("not our pad");
    return FALSE;
  }
}

/* For each buffer we receive we check if our collected condition is reached
 * and if so we call the collected function. When this is done we check if
 * data has been unqueued. If data is still queued we wait holding the stream
 * lock to make sure no EOS event can happen while we are ready to be
 * collected 
 */
static GstFlowReturn
gst_collect_pads_chain (GstPad * pad, GstBuffer * buffer)
{
  GstCollectData *data;
  GstCollectPads *pads;
  guint64 size;
  GstFlowReturn ret;
  GstBuffer **buffer_p;

  GST_DEBUG ("Got buffer for pad %s:%s", GST_DEBUG_PAD_NAME (pad));

  /* some magic to get the managing collect_pads */
  data = (GstCollectData *) gst_pad_get_element_private (pad);
  if (G_UNLIKELY (data == NULL))
    goto not_ours;

  pads = data->collect;
  size = GST_BUFFER_SIZE (buffer);

  GST_OBJECT_LOCK (pads);

  /* if not started, bail out */
  if (G_UNLIKELY (!pads->started))
    goto not_started;
  /* check if this pad is flushing */
  if (G_UNLIKELY (data->abidata.ABI.flushing))
    goto flushing;
  /* pad was EOS, we can refuse this data */
  if (G_UNLIKELY (data->abidata.ABI.eos))
    goto unexpected;

  GST_DEBUG ("Queuing buffer %p for pad %s:%s", buffer,
      GST_DEBUG_PAD_NAME (pad));

  /* One more pad has data queued */
  pads->queuedpads++;
  buffer_p = &data->buffer;
  gst_buffer_replace (buffer_p, buffer);

  /* update segment last position if in TIME */
  if (G_LIKELY (data->segment.format == GST_FORMAT_TIME)) {
    GstClockTime timestamp = GST_BUFFER_TIMESTAMP (buffer);

    if (GST_CLOCK_TIME_IS_VALID (timestamp))
      gst_segment_set_last_stop (&data->segment, GST_FORMAT_TIME, timestamp);
  }

  /* Check if our collected condition is matched and call the collected function
   * if it is */
  ret = gst_collect_pads_check_collected (pads);
  /* when an error occurs, we want to report this back to the caller ASAP
   * without having to block if the buffer was not popped */
  if (G_UNLIKELY (ret != GST_FLOW_OK))
    goto error;

  /* We still have data queued on this pad, wait for something to happen */
  while (data->buffer != NULL) {
    GST_DEBUG ("Pad %s:%s has a buffer queued, waiting",
        GST_DEBUG_PAD_NAME (pad));

    /* wait to be collected, this must happen from another thread triggered
     * by the _chain function of another pad. We release the lock so we
     * can get stopped or flushed as well. We can however not get EOS
     * because we still hold the STREAM_LOCK. */
    GST_COLLECT_PADS_WAIT (pads);

    GST_DEBUG ("Pad %s:%s resuming", GST_DEBUG_PAD_NAME (pad));

    /* after a signal, we could be stopped */
    if (G_UNLIKELY (!pads->started))
      goto not_started;
    /* check if this pad is flushing */
    if (G_UNLIKELY (data->abidata.ABI.flushing))
      goto flushing;
  }
  GST_OBJECT_UNLOCK (pads);

  return ret;

  /* ERRORS */
not_ours:
  {
    /* pretty fatal this one, can't post an error though... */
    GST_WARNING ("not our pad");
    return GST_FLOW_ERROR;
  }
not_started:
  {
    GST_OBJECT_UNLOCK (pads);
    GST_DEBUG ("not started");
    return GST_FLOW_WRONG_STATE;
  }
flushing:
  {
    GST_OBJECT_UNLOCK (pads);
    GST_DEBUG ("pad %s:%s is flushing", GST_DEBUG_PAD_NAME (pad));
    return GST_FLOW_WRONG_STATE;
  }
unexpected:
  {
    GST_OBJECT_UNLOCK (pads);
    /* we should not post an error for this, just inform upstream that
     * we don't expect anything anymore */
    GST_DEBUG ("pad %s:%s is eos", GST_DEBUG_PAD_NAME (pad));
    return GST_FLOW_UNEXPECTED;
  }
error:
  {
    GST_OBJECT_UNLOCK (pads);
    /* we print the error, the element should post a reasonable error
     * message for fatal errors */
    GST_DEBUG ("collect failed, reason %d (%s)", ret, gst_flow_get_name (ret));
    return ret;
  }
}