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 function of the pad is
 *     overridden. The element_private of the pad is used to store
 *     private information.
 *   </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.
 *   </para></listitem>
 * </itemizedlist>
 */

#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;
}

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

  gst_collect_pads_stop (pads);
  g_cond_free (pads->cond);

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

    if (pdata->pad) {
      gst_object_unref (pdata->pad);
    }
  }
  /* Free pads list */
  g_slist_free (pads->data);

  /* FIXME, free data */

  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);

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

  GST_OBJECT_LOCK (pads);
  pads->data = g_slist_append (pads->data, 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->numpads++;
  pads->cookie++;
  GST_OBJECT_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_OBJECT_LOCK (pads);
  list = g_slist_find_custom (pads->data, pad, (GCompareFunc) find_pad);
  if (list) {
    g_free (list->data);
    pads->data = g_slist_delete_link (pads->data, list);
    gst_object_unref (pad);
  }
  pads->numpads--;
  /* FIXME : if the pad has data queued we should decrease the number of
     queuedpads */
  pads->cookie++;
  GST_OBJECT_UNLOCK (pads);

  return list != NULL;
}

/**
 * gst_collect_pads_is_active:
 * @pads: the collectspads to use
 * @pad: the pad to check
 *
 * Check if a pad is active.
 *
 * 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_ERROR;
}

/**
 * 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_ERROR;
}

/**
 * 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 *walk = NULL;

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

  GST_DEBUG_OBJECT (pads, "starting collect pads");

  GST_OBJECT_LOCK (pads);
  /* Set our pads as non flushing */
  walk = pads->data;
  while (walk) {
    GstCollectData *cdata = walk->data;

    if (GST_IS_PAD (cdata->pad)) {
      GST_OBJECT_LOCK (cdata->pad);
      GST_PAD_UNSET_FLUSHING (cdata->pad);
      GST_OBJECT_UNLOCK (cdata->pad);
    }

    walk = g_slist_next (walk);
  }
  /* Start collect pads */
  pads->started = TRUE;
  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 *walk = NULL;

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

  GST_DEBUG_OBJECT (pads, "stopping collect pads");

  GST_OBJECT_LOCK (pads);
  /* Set our pads as flushing */
  walk = pads->data;
  while (walk) {
    GstCollectData *cdata = walk->data;

    if (GST_IS_PAD (cdata->pad)) {
      GST_OBJECT_LOCK (cdata->pad);
      GST_PAD_SET_FLUSHING (cdata->pad);
      GST_OBJECT_UNLOCK (cdata->pad);
    }

    walk = g_slist_next (walk);
  }
  /* Stop collect pads */
  pads->started = FALSE;
  /* Wake them up */
  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);

  result = data->buffer;

  if (result)
    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;

  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);

  result = data->buffer;
  if (result) {
    gst_buffer_replace (&data->buffer, NULL);
    data->pos = 0;
    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.
 */
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;
    gint size;

    pdata = (GstCollectData *) collected->data;

    if (pdata->buffer == NULL)
      goto not_filled;

    size = GST_BUFFER_SIZE (pdata->buffer) - pdata->pos;

    if (size < result)
      result = size;
  }
  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;

  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);

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

  *bytes = GST_BUFFER_DATA (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;

  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);

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

  data->pos += size;

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

    buf = gst_collect_pads_pop (pads, data);
    gst_buffer_unref (buf);
  }

  return flushsize;
}

static gboolean
gst_collect_pads_is_collected (GstCollectPads * pads, GstFlowReturn * ret)
{
  GstFlowReturn flow_ret = GST_FLOW_OK;
  gboolean res = FALSE;

  g_return_val_if_fail (GST_IS_COLLECT_PADS (pads), FALSE);

  /* If all our pads are EOS just collect once */
  if (pads->eospads == pads->numpads) {
    GST_DEBUG ("All active pads are EOS, calling %s",
        GST_DEBUG_FUNCPTR_NAME (pads->func));
    flow_ret = pads->func (pads, pads->user_data);
    res = TRUE;
    goto beach;
  }

  /* 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) && pads->func) {
    GST_DEBUG ("All active pads have data, calling %s",
        GST_DEBUG_FUNCPTR_NAME (pads->func));
    flow_ret = pads->func (pads, pads->user_data);
    res = TRUE;

    /* Don't keep looping after telling the element EOS or flushing */
    if (pads->queuedpads == 0)
      break;
  }

beach:
  if (!res) {
    GST_DEBUG ("Not all active pads have data, continuing");
  }

  if (ret) {
    *ret = flow_ret;
  }

  return res;
}

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

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

  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 is_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 */
      return TRUE;
    }
    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);
      GST_OBJECT_UNLOCK (pads);
      goto beach;
    }
    case GST_EVENT_EOS:
    {
      GST_OBJECT_LOCK (pads);

      pads->eospads++;

      gst_collect_pads_is_collected (pads, NULL);

      GST_OBJECT_UNLOCK (pads);

      /* We eat this event */
      gst_event_unref (event);
      return TRUE;
    }
    case GST_EVENT_NEWSEGMENT:
    {
      gint64 start, stop, time;
      gdouble rate;
      GstFormat format;
      gboolean update;

      gst_event_parse_new_segment (event, &update, &rate, &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 (&data->segment, update, rate, format,
          start, stop, time);

      data->abidata.ABI.new_segment = TRUE;

      /* We eat this event */
      gst_event_unref (event);
      return TRUE;
    }
    default:
      goto beach;
  }

beach:
  return gst_pad_event_default (pad, event);

  /* ERRORS */
not_ours:
  {
    GST_DEBUG ("collect_pads not ours");
    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;

  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 (data == NULL)
    goto not_ours;

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

  GST_OBJECT_LOCK (pads);

  /* if not started, bail out */
  if (!pads->started)
    goto not_started;
  /* check if this pad is flushing */
  if (data->abidata.ABI.flushing)
    goto flushing;

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

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

  if (data->segment.format == GST_FORMAT_TIME
      && GST_BUFFER_TIMESTAMP_IS_VALID (buffer))
    gst_segment_set_last_stop (&data->segment, GST_FORMAT_TIME,
        GST_BUFFER_TIMESTAMP (buffer));

  /* Check if our collected condition is matched and call the collected function
     if it is */
  gst_collect_pads_is_collected (pads, &ret);

  /* 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));
    GST_COLLECT_PADS_WAIT (pads);
    GST_DEBUG ("Pad %s:%s resuming", GST_DEBUG_PAD_NAME (pad));
    /* after a signal,  we could be stopped */
    if (!pads->started)
      goto not_started;
    if (data->abidata.ABI.flushing)
      goto flushing;
  }

  GST_OBJECT_UNLOCK (pads);

  return ret;

  /* ERRORS */
not_ours:
  {
    GST_DEBUG ("collect_pads not ours");
    return GST_FLOW_ERROR;
  }
not_started:
  {
    GST_OBJECT_UNLOCK (pads);
    GST_DEBUG ("collect_pads not started");
    return GST_FLOW_WRONG_STATE;
  }
flushing:
  {
    GST_OBJECT_UNLOCK (pads);
    GST_DEBUG ("collect_pads %s:%s is flushing", GST_DEBUG_PAD_NAME (pad));
    return GST_FLOW_WRONG_STATE;
  }
}