gstreamer/gst/playback/gstsubtitleoverlay.c

/*
 * Copyright (C) 2009 Sebastian Dröge <sebastian.droege@collabora.co.uk>
 *
 * 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:element-subtitleoverlay
 *
 * #GstBin that auto-magically overlays a video stream with subtitles by
 * autoplugging the required elements.
 *
 * It supports raw, timestamped text, different textual subtitle formats and
 * DVD subpicture subtitles.
 *
 * <refsect2>
 * <title>Examples</title>
 * |[
 * gst-launch -v filesrc location=test.mkv ! matroskademux name=demux ! "video/x-h264" ! queue2 ! decodebin2 ! subtitleoverlay name=overlay ! ffmpegcolorspace ! autovideosink  demux. ! "video/x-dvd-subpicture" ! queue2 ! overlay.
 * ]| This will play back the given Matroska file with h264 video and subpicture subtitles.
 * </refsect2>
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "gstsubtitleoverlay.h"

#include <gst/gstfilter.h>
#include <gst/pbutils/missing-plugins.h>
#include <gst/video/video.h>
#include <string.h>

GST_DEBUG_CATEGORY_STATIC (subtitle_overlay_debug);
#define GST_CAT_DEFAULT subtitle_overlay_debug

static GstStaticPadTemplate srctemplate = GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/x-raw-rgb; video/x-raw-yuv"));

static GstStaticPadTemplate video_sinktemplate =
    GST_STATIC_PAD_TEMPLATE ("video_sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/x-raw-rgb; video/x-raw-yuv"));

static GstStaticPadTemplate subtitle_sinktemplate =
GST_STATIC_PAD_TEMPLATE ("subtitle_sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS_ANY);

enum
{
  PROP_0,
  PROP_FONT_DESC
};

GST_BOILERPLATE (GstSubtitleOverlay, gst_subtitle_overlay, GstBin,
    GST_TYPE_BIN);

static void _pad_blocked_cb (GstPad * pad, gboolean blocked,
    gpointer user_data);

static GQuark _subtitle_overlay_event_marker_id = 0;

static void
do_async_start (GstSubtitleOverlay * self)
{
  if (!self->do_async) {
    GstMessage *msg =
        gst_message_new_async_start (GST_OBJECT_CAST (self), FALSE);

    GST_DEBUG_OBJECT (self, "Posting async-start");
    parent_class->handle_message (GST_BIN_CAST (self), msg);
    self->do_async = TRUE;
  }
}

static void
do_async_done (GstSubtitleOverlay * self)
{
  if (self->do_async) {
    GstMessage *msg = gst_message_new_async_done (GST_OBJECT_CAST (self));

    GST_DEBUG_OBJECT (self, "Posting async-done");
    parent_class->handle_message (GST_BIN_CAST (self), msg);
    self->do_async = FALSE;
  }
}

static void
gst_subtitle_overlay_finalize (GObject * object)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY (object);

  if (self->lock) {
    g_mutex_free (self->lock);
    self->lock = NULL;
  }

  if (self->font_desc) {
    g_free (self->font_desc);
    self->font_desc = NULL;
  }

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

static gboolean
_is_renderer (GstElementFactory * factory)
{
  const gchar *klass, *name;

  klass = gst_element_factory_get_klass (factory);
  name = gst_plugin_feature_get_name (GST_PLUGIN_FEATURE_CAST (factory));

  if (strstr (klass, "Overlay/Subtitle") != NULL ||
      strstr (klass, "Overlay/SubPicture") != NULL)
    return TRUE;
  if (strcmp (name, "textoverlay") == 0)
    return TRUE;
  return FALSE;
}

static gboolean
_is_parser (GstElementFactory * factory)
{
  const gchar *klass;

  klass = gst_element_factory_get_klass (factory);

  if (strstr (klass, "Parser/Subtitle") != NULL)
    return TRUE;
  return FALSE;
}

static const gchar *_sub_pad_names[] = { "subpicture", "subpicture_sink",
  "text", "text_sink",
  "subtitle_sink", "subtitle"
};

static GstCaps *
_get_sub_caps (GstElementFactory * factory)
{
  const GList *templates;
  GList *walk;
  gboolean is_parser = _is_parser (factory);

  templates = gst_element_factory_get_static_pad_templates (factory);
  for (walk = (GList *) templates; walk; walk = g_list_next (walk)) {
    GstStaticPadTemplate *templ = walk->data;

    if (templ->direction == GST_PAD_SINK && templ->presence == GST_PAD_ALWAYS) {
      gboolean found = FALSE;

      if (is_parser) {
        found = TRUE;
      } else {
        guint i;

        for (i = 0; i < G_N_ELEMENTS (_sub_pad_names); i++) {
          if (strcmp (templ->name_template, _sub_pad_names[i]) == 0) {
            found = TRUE;
            break;
          }
        }
      }
      if (found)
        return gst_static_caps_get (&templ->static_caps);
    }
  }
  return NULL;
}

static gboolean
_factory_filter (GstPluginFeature * feature, GstCaps ** subcaps)
{
  GstElementFactory *factory;
  guint rank;
  const gchar *name;
  const GList *templates;
  GList *walk;
  gboolean is_renderer;
  GstCaps *templ_caps = NULL;
  gboolean have_video_sink = FALSE;

  /* we only care about element factories */
  if (!GST_IS_ELEMENT_FACTORY (feature))
    return FALSE;

  factory = GST_ELEMENT_FACTORY_CAST (feature);

  /* only select elements with autoplugging rank or textoverlay */
  name = gst_plugin_feature_get_name (feature);
  rank = gst_plugin_feature_get_rank (feature);
  if (strcmp ("textoverlay", name) != 0 && rank < GST_RANK_MARGINAL)
    return FALSE;

  /* Check if it's a renderer or a parser */
  if (_is_renderer (factory)) {
    is_renderer = TRUE;
  } else if (_is_parser (factory)) {
    is_renderer = FALSE;
  } else {
    return FALSE;
  }

  /* Check if there's a video sink in case of a renderer */
  if (is_renderer) {
    templates = gst_element_factory_get_static_pad_templates (factory);
    for (walk = (GList *) templates; walk; walk = g_list_next (walk)) {
      GstStaticPadTemplate *templ = walk->data;

      /* we only care about the always-sink templates */
      if (templ->direction == GST_PAD_SINK && templ->presence == GST_PAD_ALWAYS) {
        if (strcmp (templ->name_template, "video") == 0 ||
            strcmp (templ->name_template, "video_sink") == 0) {
          have_video_sink = TRUE;
        }
      }
    }
  }
  templ_caps = _get_sub_caps (factory);

  if (is_renderer && have_video_sink && templ_caps) {
    GstCaps *tmp;

    GST_DEBUG ("Found renderer element %s (%s) with caps %" GST_PTR_FORMAT,
        gst_element_factory_get_longname (factory),
        gst_plugin_feature_get_name (feature), templ_caps);
    tmp = gst_caps_union (*subcaps, templ_caps);
    gst_caps_unref (templ_caps);
    gst_caps_replace (subcaps, tmp);
    gst_caps_unref (tmp);
    return TRUE;
  } else if (!is_renderer && !have_video_sink && templ_caps) {
    GstCaps *tmp;

    GST_DEBUG ("Found parser element %s (%s) with caps %" GST_PTR_FORMAT,
        gst_element_factory_get_longname (factory),
        gst_plugin_feature_get_name (feature), templ_caps);
    tmp = gst_caps_union (*subcaps, templ_caps);
    gst_caps_unref (templ_caps);
    gst_caps_replace (subcaps, tmp);
    gst_caps_unref (tmp);
    return TRUE;
  } else {
    if (templ_caps)
      gst_caps_unref (templ_caps);
    return FALSE;
  }
}

static gboolean
gst_subtitle_overlay_create_factory_list (GstSubtitleOverlay * self)
{
  if (g_once_init_enter ((gsize *) & self->factories)) {
    GstCaps *subcaps;
    GList *factories;

    subcaps = gst_caps_new_empty ();

    factories = gst_default_registry_feature_filter (
        (GstPluginFeatureFilter) _factory_filter, FALSE, &subcaps);
    GST_DEBUG_OBJECT (self, "Created factory caps: %" GST_PTR_FORMAT, subcaps);
    gst_caps_replace (&self->factory_caps, subcaps);
    gst_caps_unref (subcaps);
    g_once_init_leave ((gsize *) & self->factories, (gsize) factories);
  }

  return (self->factories != NULL);
}

GstCaps *
gst_subtitle_overlay_create_factory_caps (void)
{
  GList *factories;
  GstCaps *subcaps;

  subcaps = gst_caps_new_empty ();

  factories = gst_default_registry_feature_filter (
      (GstPluginFeatureFilter) _factory_filter, FALSE, &subcaps);
  GST_DEBUG ("Created factory caps: %" GST_PTR_FORMAT, subcaps);
  gst_plugin_feature_list_free (factories);

  return subcaps;
}

static gboolean
_filter_factories_for_caps (GstElementFactory * factory, const GstCaps * caps)
{
  GstCaps *fcaps = _get_sub_caps (factory);
  gboolean ret = (fcaps) ? gst_caps_can_intersect (fcaps, caps) : FALSE;

  if (fcaps)
    gst_caps_unref (fcaps);
  return ret;
}

static gint
_sort_by_ranks (GstPluginFeature * f1, GstPluginFeature * f2)
{
  gint diff;
  const gchar *rname1, *rname2;

  diff = gst_plugin_feature_get_rank (f2) - gst_plugin_feature_get_rank (f1);
  if (diff != 0)
    return diff;

  /* If the ranks are the same sort by name to get deterministic results */
  rname1 = gst_plugin_feature_get_name (f1);
  rname2 = gst_plugin_feature_get_name (f2);

  diff = strcmp (rname1, rname2);

  return diff;
}

static GstPad *
_get_sub_pad (GstElement * element)
{
  GstPad *pad;
  guint i;

  for (i = 0; i < G_N_ELEMENTS (_sub_pad_names); i++) {
    pad = gst_element_get_static_pad (element, _sub_pad_names[i]);
    if (pad)
      return pad;
  }
  return NULL;
}

static GstPad *
_get_video_pad (GstElement * element)
{
  static const gchar *pad_names[] = { "video", "video_sink" };
  GstPad *pad;
  guint i;

  for (i = 0; i < G_N_ELEMENTS (pad_names); i++) {
    pad = gst_element_get_static_pad (element, pad_names[i]);
    if (pad)
      return pad;
  }
  return NULL;
}

static gboolean
_create_element (GstSubtitleOverlay * self, GstElement ** element,
    const gchar * factory_name, GstElementFactory * factory,
    const gchar * element_name, gboolean mandatory)
{
  GstElement *elt;

  g_assert (!factory || !factory_name);

  if (factory_name) {
    elt = gst_element_factory_make (factory_name, element_name);
  } else {
    factory_name =
        gst_plugin_feature_get_name (GST_PLUGIN_FEATURE_CAST (factory));
    elt = gst_element_factory_create (factory, element_name);
  }

  if (G_UNLIKELY (!elt)) {
    if (!factory) {
      GstMessage *msg;

      msg =
          gst_missing_element_message_new (GST_ELEMENT_CAST (self),
          factory_name);
      gst_element_post_message (GST_ELEMENT_CAST (self), msg);

      if (mandatory)
        GST_ELEMENT_ERROR (self, CORE, MISSING_PLUGIN, (NULL),
            ("no '%s' plugin found", factory_name));
      else
        GST_ELEMENT_WARNING (self, CORE, MISSING_PLUGIN, (NULL),
            ("no '%s' plugin found", factory_name));
    } else {
      if (mandatory) {
        GST_ELEMENT_ERROR (self, CORE, FAILED, (NULL),
            ("can't instantiate '%s'", factory_name));
      } else {
        GST_ELEMENT_WARNING (self, CORE, FAILED, (NULL),
            ("can't instantiate '%s'", factory_name));
      }
    }

    return FALSE;
  }

  if (G_UNLIKELY (gst_element_set_state (elt,
              GST_STATE_READY) != GST_STATE_CHANGE_SUCCESS)) {
    gst_object_unref (elt);
    if (mandatory) {
      GST_ELEMENT_ERROR (self, CORE, STATE_CHANGE, (NULL),
          ("failed to set '%s' to READY", factory_name));
    } else {
      GST_WARNING_OBJECT (self, "Failed to set '%s' to READY", factory_name);
    }
    return FALSE;
  }

  if (G_UNLIKELY (!gst_bin_add (GST_BIN_CAST (self), gst_object_ref (elt)))) {
    gst_element_set_state (elt, GST_STATE_NULL);
    gst_object_unref (elt);
    if (mandatory) {
      GST_ELEMENT_ERROR (self, CORE, FAILED, (NULL),
          ("failed to add '%s' to subtitleoverlay", factory_name));
    } else {
      GST_WARNING_OBJECT (self, "Failed to add '%s' to subtitleoverlay",
          factory_name);
    }
    return FALSE;
  }

  gst_element_sync_state_with_parent (elt);
  *element = elt;
  return TRUE;
}

static void
_remove_element (GstSubtitleOverlay * self, GstElement ** element)
{
  if (*element) {
    gst_bin_remove (GST_BIN_CAST (self), *element);
    gst_element_set_state (*element, GST_STATE_NULL);
    gst_object_unref (*element);
    *element = NULL;
  }
}

static void
_generate_update_newsegment_event (GstSegment * segment, GstEvent ** event1,
    GstEvent ** event2)
{
  GstEvent *event;

  *event1 = NULL;
  *event2 = NULL;

  event = gst_event_new_new_segment_full (FALSE, segment->rate,
      segment->applied_rate, segment->format, 0, segment->accum, 0);
  gst_structure_id_set (event->structure, _subtitle_overlay_event_marker_id,
      G_TYPE_BOOLEAN, TRUE, NULL);
  *event1 = event;

  event = gst_event_new_new_segment_full (FALSE, segment->rate,
      segment->applied_rate, segment->format,
      segment->start, segment->stop, segment->time);
  gst_structure_id_set (event->structure, _subtitle_overlay_event_marker_id,
      G_TYPE_BOOLEAN, TRUE, NULL);
  *event2 = event;
}

static gboolean
_setup_passthrough (GstSubtitleOverlay * self)
{
  GstPad *src, *sink;
  GstElement *identity;

  GST_DEBUG_OBJECT (self, "Doing video passthrough");

  if (self->passthrough_identity) {
    GST_DEBUG_OBJECT (self, "Already in passthrough mode");
    goto out;
  }

  /* Unlink & destroy everything */
  gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->srcpad), NULL);
  gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->video_sinkpad), NULL);
  gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->subtitle_sinkpad), NULL);
  _remove_element (self, &self->post_colorspace);
  _remove_element (self, &self->overlay);
  _remove_element (self, &self->parser);
  _remove_element (self, &self->renderer);
  _remove_element (self, &self->pre_colorspace);
  _remove_element (self, &self->passthrough_identity);

  if (G_UNLIKELY (!_create_element (self, &self->passthrough_identity,
              "identity", NULL, "passthrough-identity", TRUE))) {
    return FALSE;
  }

  identity = self->passthrough_identity;
  g_object_set (G_OBJECT (identity), "silent", TRUE, "signal-handoffs", FALSE,
      NULL);

  /* Set src ghostpad target */
  src = gst_element_get_static_pad (self->passthrough_identity, "src");
  if (G_UNLIKELY (!src)) {
    GST_ELEMENT_ERROR (self, CORE, PAD, (NULL),
        ("Failed to get srcpad from identity"));
    return FALSE;
  }

  if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->srcpad),
              src))) {
    GST_ELEMENT_ERROR (self, CORE, PAD, (NULL),
        ("Failed to set srcpad target"));
    gst_object_unref (src);
    return FALSE;
  }
  gst_object_unref (src);

  sink = gst_element_get_static_pad (self->passthrough_identity, "sink");
  if (G_UNLIKELY (!sink)) {
    GST_ELEMENT_ERROR (self, CORE, PAD, (NULL),
        ("Failed to get sinkpad from identity"));
    return FALSE;
  }

  /* Send segment to the identity. This is dropped because identity
   * is not linked downstream yet */
  if (!self->video_segment_pending) {
    GstEvent *event1, *event2;

    _generate_update_newsegment_event (&self->video_segment, &event1, &event2);
    GST_DEBUG_OBJECT (self,
        "Pushing video accumulate newsegment event: %" GST_PTR_FORMAT,
        event1->structure);
    GST_DEBUG_OBJECT (self,
        "Pushing video update newsegment event: %" GST_PTR_FORMAT,
        event2->structure);
    gst_pad_send_event (sink, event1);
    gst_pad_send_event (sink, event2);
  }

  /* Link sink ghostpads to identity */
  if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST
              (self->video_sinkpad), sink))) {
    GST_ELEMENT_ERROR (self, CORE, PAD, (NULL),
        ("Failed to set video sinkpad target"));
    gst_object_unref (sink);
    return FALSE;
  }
  gst_object_unref (sink);

  GST_DEBUG_OBJECT (self, "Video passthrough setup successfully");

out:
  /* Unblock pads */
  gst_pad_set_blocked_async_full (self->video_block_pad, FALSE,
      _pad_blocked_cb, gst_object_ref (self),
      (GDestroyNotify) gst_object_unref);

  if (self->subtitle_sink_blocked)
    gst_pad_set_blocked_async_full (self->subtitle_block_pad, FALSE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);

  return TRUE;
}

static void
_pad_blocked_cb (GstPad * pad, gboolean blocked, gpointer user_data)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY_CAST (user_data);
  GstCaps *subcaps;
  GList *l, *factories = NULL;

  GST_DEBUG_OBJECT (pad, "Pad blocked: %d", blocked);

  GST_SUBTITLE_OVERLAY_LOCK (self);
  if (pad == self->video_block_pad)
    self->video_sink_blocked = blocked;
  else if (pad == self->subtitle_block_pad)
    self->subtitle_sink_blocked = blocked;

  if (!blocked) {
    GST_SUBTITLE_OVERLAY_UNLOCK (self);
    return;
  }

  /* Now either both or the video sink are blocked */

  /* Get current subtitle caps */
  subcaps = self->subcaps;
  if (!subcaps) {
    GstPad *peer;

    peer = gst_pad_get_peer (self->subtitle_sinkpad);
    if (peer) {
      subcaps = gst_pad_get_negotiated_caps (peer);
      if (!subcaps) {
        subcaps = gst_pad_get_caps (peer);
        if (!gst_caps_is_fixed (subcaps)) {
          gst_caps_unref (subcaps);
          subcaps = NULL;
        }
      }
      gst_object_unref (peer);
    }
    gst_caps_replace (&self->subcaps, subcaps);
    if (subcaps)
      gst_caps_unref (subcaps);
  }
  GST_DEBUG_OBJECT (self, "Current subtitle caps: %" GST_PTR_FORMAT, subcaps);

  /* If there are no subcaps but the subtitle sink is blocked upstream
   * must behave wrong as there are no fixed caps set for the first
   * buffer or in-order event */
  if (G_UNLIKELY (!subcaps && self->subtitle_sink_blocked)) {
    GST_ELEMENT_WARNING (self, CORE, NEGOTIATION, (NULL),
        ("Subtitle sink is blocked but we have no subtitle caps"));
    subcaps = NULL;
  }

  /* Now do something with the caps */
  if (subcaps && !self->subtitle_flush) {
    GstPad *target =
        gst_ghost_pad_get_target (GST_GHOST_PAD_CAST (self->subtitle_sinkpad));

    if (target && gst_pad_accept_caps (target, subcaps)) {
      GST_DEBUG_OBJECT (pad, "Target accepts caps");

      gst_object_unref (target);

      /* Unblock pads */
      gst_pad_set_blocked_async_full (self->video_block_pad, FALSE,
          _pad_blocked_cb, gst_object_ref (self),
          (GDestroyNotify) gst_object_unref);

      if (self->subtitle_sink_blocked)
        gst_pad_set_blocked_async_full (self->subtitle_block_pad, FALSE,
            _pad_blocked_cb, gst_object_ref (self),
            (GDestroyNotify) gst_object_unref);
      goto out;
    } else if (target) {
      gst_object_unref (target);
    }
  }

  if (self->subtitle_sink_blocked && !self->video_sink_blocked) {
    GST_DEBUG_OBJECT (self, "Subtitle sink blocked but video not blocked");
    gst_pad_set_blocked_async_full (self->video_block_pad, TRUE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);
    goto out;
  }

  self->subtitle_flush = FALSE;

  /* Find our factories */
  if (subcaps) {
    factories = gst_filter_run (self->factories,
        (GstFilterFunc) _filter_factories_for_caps, FALSE, subcaps);
    if (!factories) {
      GstMessage *msg;

      msg = gst_missing_decoder_message_new (GST_ELEMENT_CAST (self), subcaps);
      gst_element_post_message (GST_ELEMENT_CAST (self), msg);
      GST_ELEMENT_WARNING (self, CORE, MISSING_PLUGIN, (NULL),
          ("no suitable subtitle plugin found"));
      subcaps = NULL;
    }
  }

  if (!subcaps) {
    _setup_passthrough (self);
    do_async_done (self);
    goto out;
  }

  /* Now the interesting parts are done: subtitle overlaying! */

  /* Sort the factories by rank */
  factories = g_list_sort (factories, (GCompareFunc) _sort_by_ranks);

  for (l = factories; l; l = l->next) {
    GstElementFactory *factory = l->data;
    gboolean is_renderer = _is_renderer (factory);
    GstElement *element;
    GstPad *sink, *src;

    /* Unlink & destroy everything */

    gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->srcpad), NULL);
    gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->video_sinkpad), NULL);
    gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->subtitle_sinkpad),
        NULL);
    _remove_element (self, &self->post_colorspace);
    _remove_element (self, &self->overlay);
    _remove_element (self, &self->parser);
    _remove_element (self, &self->renderer);
    _remove_element (self, &self->pre_colorspace);
    _remove_element (self, &self->passthrough_identity);

    GST_DEBUG_OBJECT (self, "Trying factory '%s'",
        GST_STR_NULL (gst_plugin_feature_get_name (GST_PLUGIN_FEATURE_CAST
                (factory))));

    if (G_UNLIKELY ((is_renderer
                && !_create_element (self, &self->renderer, NULL, factory,
                    "renderer", FALSE)) || (!is_renderer
                && !_create_element (self, &self->parser, NULL, factory,
                    "parser", FALSE))))
      continue;

    element = is_renderer ? self->renderer : self->parser;

    /* If this is a parser, create textoverlay and link video and the parser to it
     * Else link the renderer to the output colorspace */
    if (!is_renderer) {
      GstElement *overlay;

      /* First link everything internally */
      if (G_UNLIKELY (!_create_element (self, &self->overlay, "textoverlay",
                  NULL, "overlay", FALSE))) {
        continue;
      }
      overlay = self->overlay;

      /* Set some properties */
      g_object_set (G_OBJECT (overlay),
          "halign", "center", "valign", "bottom", "wait-text", FALSE, NULL);
      if (self->font_desc)
        g_object_set (G_OBJECT (overlay), "font-desc", self->font_desc, NULL);

      src = gst_element_get_static_pad (element, "src");
      if (G_UNLIKELY (!src)) {
        continue;
      }

      sink = gst_element_get_static_pad (overlay, "text_sink");
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Can't get text sink from textoverlay");
        gst_object_unref (src);
      }

      if (G_UNLIKELY (gst_pad_link (src, sink) != GST_PAD_LINK_OK)) {
        GST_WARNING_OBJECT (self, "Can't link parser to textoverlay");
        gst_object_unref (sink);
        gst_object_unref (src);
      }
      gst_object_unref (sink);
      gst_object_unref (src);

      if (G_UNLIKELY (!_create_element (self, &self->post_colorspace,
                  "ffmpegcolorspace", NULL, "post-colorspace", FALSE))) {
        continue;
      }

      src = gst_element_get_static_pad (overlay, "src");
      if (G_UNLIKELY (!src)) {
        GST_WARNING_OBJECT (self, "Can't get src pad from overlay");
        continue;
      }

      sink = gst_element_get_static_pad (self->post_colorspace, "sink");
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Can't get sink pad from ffmpegcolorspace");
        gst_object_unref (src);
        continue;
      }

      if (G_UNLIKELY (gst_pad_link (src, sink) != GST_PAD_LINK_OK)) {
        GST_WARNING_OBJECT (self, "Can't link overlay with ffmpegcolorspace");
        gst_object_unref (src);
        gst_object_unref (sink);
        continue;
      }
      gst_object_unref (src);
      gst_object_unref (sink);

      if (G_UNLIKELY (!_create_element (self, &self->pre_colorspace,
                  "ffmpegcolorspace", NULL, "pre-colorspace", FALSE))) {
        continue;
      }

      sink = gst_element_get_static_pad (overlay, "video_sink");
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Can't get video sink from textoverlay");
        continue;
      }

      src = gst_element_get_static_pad (self->pre_colorspace, "src");
      if (G_UNLIKELY (!src)) {
        GST_WARNING_OBJECT (self, "Can't get srcpad from ffmpegcolorspace");
        gst_object_unref (sink);
        continue;
      }

      if (G_UNLIKELY (gst_pad_link (src, sink) != GST_PAD_LINK_OK)) {
        GST_WARNING_OBJECT (self, "Can't link ffmpegcolorspace to textoverlay");
        gst_object_unref (src);
        gst_object_unref (sink);
        continue;
      }
      gst_object_unref (src);
      gst_object_unref (sink);

      /* Set src ghostpad target */
      src = gst_element_get_static_pad (self->post_colorspace, "src");
      if (G_UNLIKELY (!src)) {
        GST_WARNING_OBJECT (self, "Can't get src pad from ffmpegcolorspace");
        continue;
      }

      if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST
                  (self->srcpad), src))) {
        GST_WARNING_OBJECT (self, "Can't set srcpad target");
        gst_object_unref (src);
        continue;
      }
      gst_object_unref (src);

      /* Send segments to the parser/overlay if necessary. These are not sent
       * outside this element because of the proxy pad event function */
      if (!self->video_segment_pending) {
        GstEvent *event1, *event2;

        sink = gst_element_get_static_pad (self->pre_colorspace, "sink");
        if (G_UNLIKELY (!sink)) {
          GST_WARNING_OBJECT (self, "Can't get sink pad from ffmpegcolorspace");
          continue;
        }

        _generate_update_newsegment_event (&self->video_segment, &event1,
            &event2);
        GST_DEBUG_OBJECT (self,
            "Pushing video accumulate newsegment event: %" GST_PTR_FORMAT,
            event1->structure);
        GST_DEBUG_OBJECT (self,
            "Pushing video update newsegment event: %" GST_PTR_FORMAT,
            event2->structure);
        gst_pad_send_event (sink, event1);
        gst_pad_send_event (sink, event2);

        gst_object_unref (sink);
      }

      if (!self->subtitle_segment_pending) {
        GstEvent *event1, *event2;

        sink = gst_element_get_static_pad (element, "sink");
        if (G_UNLIKELY (!sink)) {
          GST_WARNING_OBJECT (self, "Failed to get subpad");
          continue;
        }

        _generate_update_newsegment_event (&self->subtitle_segment, &event1,
            &event2);
        GST_DEBUG_OBJECT (self,
            "Pushing subtitle accumulate newsegment event: %" GST_PTR_FORMAT,
            event1->structure);
        GST_DEBUG_OBJECT (self,
            "Pushing subtitle update newsegment event: %" GST_PTR_FORMAT,
            event2->structure);
        gst_pad_send_event (sink, event1);
        gst_pad_send_event (sink, event2);

        gst_object_unref (sink);
      }

      /* Set the sink ghostpad targets */
      sink = gst_element_get_static_pad (self->pre_colorspace, "sink");
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Can't get sink pad from ffmpegcolorspace");
        continue;
      }

      if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST
                  (self->video_sinkpad), sink))) {
        GST_WARNING_OBJECT (self, "Can't set video sinkpad target");
        gst_object_unref (sink);
        continue;
      }
      gst_object_unref (sink);

      /* Link subtitle identity to subtitle pad of our element */
      sink = gst_element_get_static_pad (element, "sink");
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Failed to get subpad");
        continue;
      }

      if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST
                  (self->subtitle_sinkpad), sink))) {
        GST_WARNING_OBJECT (self, "Failed to set subtitle sink target");
        gst_object_unref (sink);
        continue;
      }
      gst_object_unref (sink);
    } else {
      const gchar *name =
          gst_plugin_feature_get_name (GST_PLUGIN_FEATURE_CAST (factory));

      if (strcmp (name, "textoverlay") == 0) {
        /* Set some textoverlay specific properties */
        g_object_set (G_OBJECT (element),
            "halign", "center", "valign", "bottom", "wait-text", FALSE, NULL);
        if (self->font_desc)
          g_object_set (G_OBJECT (element), "font-desc", self->font_desc, NULL);
      }

      /* First link everything internally */
      if (G_UNLIKELY (!_create_element (self, &self->post_colorspace,
                  "ffmpegcolorspace", NULL, "post-colorspace", FALSE))) {
        continue;
      }

      src = gst_element_get_static_pad (element, "src");
      if (G_UNLIKELY (!src)) {
        GST_WARNING_OBJECT (self, "Can't get src pad from renderer");
        continue;
      }

      sink = gst_element_get_static_pad (self->post_colorspace, "sink");
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Can't get sink pad from ffmpegcolorspace");
        gst_object_unref (src);
        continue;
      }

      if (G_UNLIKELY (gst_pad_link (src, sink) != GST_PAD_LINK_OK)) {
        GST_WARNING_OBJECT (self, "Can't link renderer with ffmpegcolorspace");
        gst_object_unref (src);
        gst_object_unref (sink);
        continue;
      }
      gst_object_unref (src);
      gst_object_unref (sink);

      if (G_UNLIKELY (!_create_element (self, &self->pre_colorspace,
                  "ffmpegcolorspace", NULL, "pre-colorspace", FALSE))) {
        continue;
      }

      sink = _get_video_pad (element);
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Can't get video sink from renderer");
        continue;
      }

      src = gst_element_get_static_pad (self->pre_colorspace, "src");
      if (G_UNLIKELY (!src)) {
        GST_WARNING_OBJECT (self, "Can't get srcpad from ffmpegcolorspace");
        gst_object_unref (sink);
        continue;
      }

      if (G_UNLIKELY (gst_pad_link (src, sink) != GST_PAD_LINK_OK)) {
        GST_WARNING_OBJECT (self, "Can't link ffmpegcolorspace to renderer");
        gst_object_unref (src);
        gst_object_unref (sink);
        continue;
      }
      gst_object_unref (src);
      gst_object_unref (sink);

      /* Set src ghostpad target */
      src = gst_element_get_static_pad (self->post_colorspace, "src");
      if (G_UNLIKELY (!src)) {
        GST_WARNING_OBJECT (self, "Can't get src pad from ffmpegcolorspace");
        continue;
      }

      if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST
                  (self->srcpad), src))) {
        GST_WARNING_OBJECT (self, "Can't set srcpad target");
        gst_object_unref (src);
        continue;
      }
      gst_object_unref (src);

      /* Send segments to the renderer if necessary. These are not sent
       * outside this element because of the proxy pad event handler */
      if (!self->video_segment_pending) {
        GstEvent *event1, *event2;

        sink = gst_element_get_static_pad (self->pre_colorspace, "sink");
        if (G_UNLIKELY (!sink)) {
          GST_WARNING_OBJECT (self, "Can't get sink pad from ffmpegcolorspace");
          continue;
        }

        _generate_update_newsegment_event (&self->video_segment, &event1,
            &event2);
        GST_DEBUG_OBJECT (self,
            "Pushing video accumulate newsegment event: %" GST_PTR_FORMAT,
            event1->structure);
        GST_DEBUG_OBJECT (self,
            "Pushing video update newsegment event: %" GST_PTR_FORMAT,
            event2->structure);
        gst_pad_send_event (sink, event1);
        gst_pad_send_event (sink, event2);
        gst_object_unref (sink);
      }

      if (!self->subtitle_segment_pending) {
        GstEvent *event1, *event2;

        sink = _get_sub_pad (element);
        if (G_UNLIKELY (!sink)) {
          GST_WARNING_OBJECT (self, "Failed to get subpad");
          continue;
        }

        _generate_update_newsegment_event (&self->subtitle_segment, &event1,
            &event2);
        GST_DEBUG_OBJECT (self,
            "Pushing subtitle accumulate newsegment event: %" GST_PTR_FORMAT,
            event1->structure);
        GST_DEBUG_OBJECT (self,
            "Pushing subtitle update newsegment event: %" GST_PTR_FORMAT,
            event2->structure);
        gst_pad_send_event (sink, event1);
        gst_pad_send_event (sink, event2);
        gst_object_unref (sink);
      }

      /* Set the sink ghostpad targets */
      sink = gst_element_get_static_pad (self->pre_colorspace, "sink");
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Can't get sink pad from ffmpegcolorspace");
        continue;
      }

      if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST
                  (self->video_sinkpad), sink))) {
        GST_WARNING_OBJECT (self, "Can't set video sinkpad target");
        gst_object_unref (sink);
        continue;
      }

      sink = _get_sub_pad (element);
      if (G_UNLIKELY (!sink)) {
        GST_WARNING_OBJECT (self, "Failed to get subpad");
        continue;
      }

      if (G_UNLIKELY (!gst_ghost_pad_set_target (GST_GHOST_PAD_CAST
                  (self->subtitle_sinkpad), sink))) {
        GST_WARNING_OBJECT (self, "Failed to set subtitle sink target");
        gst_object_unref (sink);
        continue;
      }
      gst_object_unref (sink);
    }

    break;
  }

  if (G_UNLIKELY (l == NULL)) {
    GST_ELEMENT_WARNING (self, CORE, FAILED, (NULL),
        ("Failed to find any usable factories"));
    _setup_passthrough (self);
    do_async_done (self);
  } else {
    GST_DEBUG_OBJECT (self, "Everything worked, unblocking pads");
    gst_pad_set_blocked_async_full (self->video_block_pad, FALSE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);
    gst_pad_set_blocked_async_full (self->subtitle_block_pad, FALSE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);
    do_async_done (self);
  }

out:
  if (factories)
    g_list_free (factories);
  GST_SUBTITLE_OVERLAY_UNLOCK (self);
}

static GstStateChangeReturn
gst_subtitle_overlay_change_state (GstElement * element,
    GstStateChange transition)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY (element);
  GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;

  switch (transition) {
    case GST_STATE_CHANGE_NULL_TO_READY:
      GST_DEBUG_OBJECT (self, "State change NULL->READY");
      if (G_UNLIKELY (!gst_subtitle_overlay_create_factory_list (self)))
        return GST_STATE_CHANGE_FAILURE;

      GST_SUBTITLE_OVERLAY_LOCK (self);
      /* Set the internal pads to blocking */
      gst_pad_set_blocked_async_full (self->video_block_pad, TRUE,
          _pad_blocked_cb, gst_object_ref (self),
          (GDestroyNotify) gst_object_unref);
      gst_pad_set_blocked_async_full (self->subtitle_block_pad, TRUE,
          _pad_blocked_cb, gst_object_ref (self),
          (GDestroyNotify) gst_object_unref);
      GST_SUBTITLE_OVERLAY_UNLOCK (self);
      break;
    case GST_STATE_CHANGE_READY_TO_PAUSED:
      GST_DEBUG_OBJECT (self, "State change READY->PAUSED");
      gst_segment_init (&self->video_segment, GST_FORMAT_UNDEFINED);
      gst_segment_init (&self->subtitle_segment, GST_FORMAT_UNDEFINED);

      self->video_segment_pending = FALSE;
      self->subtitle_segment_pending = FALSE;
      self->subtitle_flush = FALSE;

      do_async_start (self);
      ret = GST_STATE_CHANGE_ASYNC;

      break;
    case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
      GST_DEBUG_OBJECT (self, "State change PAUSED->PLAYING");
    default:
      break;
  }

  {
    GstStateChangeReturn bret;

    bret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
    GST_DEBUG_OBJECT (self, "Base class state changed returned: %d", bret);
    if (G_UNLIKELY (bret == GST_STATE_CHANGE_FAILURE))
      return ret;
    else if (bret == GST_STATE_CHANGE_ASYNC)
      ret = bret;
    else if (G_UNLIKELY (bret == GST_STATE_CHANGE_NO_PREROLL)) {
      do_async_done (self);
      ret = bret;
    }
  }

  switch (transition) {
    case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
      GST_DEBUG_OBJECT (self, "State change PLAYING->PAUSED");
      break;
    case GST_STATE_CHANGE_PAUSED_TO_READY:
      GST_DEBUG_OBJECT (self, "State change PAUSED->READY");
      do_async_done (self);

      break;
    case GST_STATE_CHANGE_READY_TO_NULL:{
      GstPad *pad;

      GST_DEBUG_OBJECT (self, "State change READY->NULL");

      if (self->factories)
        gst_plugin_feature_list_free (self->factories);
      self->factories = NULL;
      gst_caps_replace (&self->factory_caps, NULL);

      GST_SUBTITLE_OVERLAY_LOCK (self);
      gst_caps_replace (&self->subcaps, NULL);

      /* Unlink ghost pads */
      gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->srcpad), NULL);
      gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->video_sinkpad), NULL);
      gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (self->subtitle_sinkpad),
          NULL);

      /* Unblock pads */
      if (self->video_block_pad) {
        pad = self->video_block_pad;
        gst_pad_set_blocked_async_full (pad, FALSE, _pad_blocked_cb,
            gst_object_ref (self), (GDestroyNotify) gst_object_unref);
      }

      if (self->subtitle_block_pad) {
        pad = self->subtitle_block_pad;
        gst_pad_set_blocked_async_full (pad, FALSE, _pad_blocked_cb,
            gst_object_ref (self), (GDestroyNotify) gst_object_unref);
      }

      /* Remove elements */
      _remove_element (self, &self->post_colorspace);
      _remove_element (self, &self->overlay);
      _remove_element (self, &self->parser);
      _remove_element (self, &self->renderer);
      _remove_element (self, &self->pre_colorspace);
      _remove_element (self, &self->passthrough_identity);
      GST_SUBTITLE_OVERLAY_UNLOCK (self);

      break;
    }
    default:
      break;
  }

  return ret;
}

static void
gst_subtitle_overlay_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY_CAST (object);

  switch (prop_id) {
    case PROP_FONT_DESC:
      GST_SUBTITLE_OVERLAY_LOCK (self);
      g_free (self->font_desc);
      self->font_desc = g_value_dup_string (value);
      GST_SUBTITLE_OVERLAY_UNLOCK (self);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_subtitle_overlay_base_init (gpointer g_class)
{
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (g_class);

  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&srctemplate));

  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&video_sinktemplate));
  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&subtitle_sinktemplate));

  gst_element_class_set_details_simple (gstelement_class, "Subtitle Overlay",
      "Video/Overlay/Subtitle",
      "Overlays a video stream with subtitles",
      "Sebastian Dröge <sebastian.droege@collabora.co.uk>");
}

static void
gst_subtitle_overlay_class_init (GstSubtitleOverlayClass * klass)
{
  GObjectClass *gobject_class = (GObjectClass *) klass;
  GstElementClass *element_class = (GstElementClass *) klass;

  gobject_class->finalize = gst_subtitle_overlay_finalize;
  gobject_class->set_property = gst_subtitle_overlay_set_property;

  g_object_class_install_property (gobject_class, PROP_FONT_DESC,
      g_param_spec_string ("font-desc",
          "Subtitle font description",
          "Pango font description of font "
          "to be used for subtitle rendering", NULL,
          G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));

  element_class->change_state =
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_change_state);
}

static gboolean
gst_subtitle_overlay_src_proxy_event (GstPad * proxypad, GstEvent * event)
{
  GstPad *ghostpad = NULL;
  GstSubtitleOverlay *self = NULL;
  gboolean ret = FALSE;
  const GstStructure *s;

  ghostpad = GST_PAD_CAST (gst_pad_get_parent (proxypad));
  if (G_UNLIKELY (!ghostpad))
    goto out;
  self = GST_SUBTITLE_OVERLAY_CAST (gst_pad_get_parent (ghostpad));
  if (G_UNLIKELY (!self || self->srcpad != ghostpad))
    goto out;

  s = gst_event_get_structure (event);
  if (s && gst_structure_id_has_field (s, _subtitle_overlay_event_marker_id)) {
    GST_DEBUG_OBJECT (ghostpad, "Dropping event with marker: %" GST_PTR_FORMAT,
        event->structure);
    gst_event_unref (event);
    event = NULL;
    ret = TRUE;
  } else {
    ret = self->src_proxy_event (proxypad, event);
    event = NULL;
  }

out:
  if (event)
    gst_event_unref (event);
  if (self)
    gst_object_unref (self);
  if (ghostpad)
    gst_object_unref (ghostpad);
  return ret;
}

static gboolean
gst_subtitle_overlay_video_sink_event (GstPad * pad, GstEvent * event)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY (gst_pad_get_parent (pad));
  gboolean ret;
  gboolean is_newsegment_event = FALSE;

  if (GST_EVENT_TYPE (event) == GST_EVENT_NEWSEGMENT) {
    gboolean update;
    gdouble rate, applied_rate;
    GstFormat format;
    gint64 start, stop, position;

    GST_DEBUG_OBJECT (pad, "Newsegment event: %" GST_PTR_FORMAT,
        event->structure);
    gst_event_parse_new_segment_full (event, &update, &rate, &applied_rate,
        &format, &start, &stop, &position);

    if (format != GST_FORMAT_TIME) {
      GST_ERROR_OBJECT (pad, "Newsegment event in non-time format: %s",
          gst_format_get_name (format));
      gst_object_unref (event);
      gst_object_unref (self);
      return FALSE;
    }

    GST_DEBUG_OBJECT (pad, "Old video segment: %" GST_SEGMENT_FORMAT,
        &self->video_segment);
    gst_segment_set_newsegment_full (&self->video_segment, update, rate,
        applied_rate, format, start, stop, position);
    GST_DEBUG_OBJECT (pad, "New video segment: %" GST_SEGMENT_FORMAT,
        &self->video_segment);
    is_newsegment_event = TRUE;
  } else if (GST_EVENT_TYPE (event) == GST_EVENT_FLUSH_STOP) {
    GST_DEBUG_OBJECT (pad,
        "Resetting video segment because of flush-stop event");
    gst_segment_init (&self->video_segment, GST_FORMAT_UNDEFINED);
  }

  if (is_newsegment_event)
    self->video_segment_pending = TRUE;
  ret = self->video_sink_event (pad, event);
  self->video_segment_pending = FALSE;

  gst_object_unref (self);
  return ret;
}

static GstCaps *
gst_subtitle_overlay_subtitle_sink_getcaps (GstPad * pad)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY (gst_pad_get_parent (pad));
  GstCaps *ret;

  if (G_UNLIKELY (!gst_subtitle_overlay_create_factory_list (self)))
    ret = GST_CAPS_NONE;
  else
    ret = gst_caps_ref (self->factory_caps);

  GST_DEBUG_OBJECT (pad, "Returning subtitle caps %" GST_PTR_FORMAT, ret);

  gst_object_unref (self);

  return ret;
}

static gboolean
gst_subtitle_overlay_subtitle_sink_acceptcaps (GstPad * pad, GstCaps * caps)
{
  GstCaps *othercaps = gst_subtitle_overlay_subtitle_sink_getcaps (pad);
  gboolean ret = gst_caps_can_intersect (caps, othercaps);

  gst_caps_unref (othercaps);

  return ret;
}

static gboolean
gst_subtitle_overlay_subtitle_sink_setcaps (GstPad * pad, GstCaps * caps)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY (gst_pad_get_parent (pad));
  gboolean ret = TRUE;
  GstPad *target = NULL;;

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

  target =
      gst_ghost_pad_get_target (GST_GHOST_PAD_CAST (self->subtitle_sinkpad));

  GST_SUBTITLE_OVERLAY_LOCK (self);
  gst_caps_replace (&self->subcaps, caps);

  if (target && gst_pad_accept_caps (target, caps)) {
    GST_DEBUG_OBJECT (pad, "Target accepts caps");
    ret = self->subtitle_sink_setcaps (pad, caps);
    GST_SUBTITLE_OVERLAY_UNLOCK (self);
    goto out;
  }

  GST_DEBUG_OBJECT (pad, "Target did not accept caps");

  gst_pad_set_blocked_async_full (self->subtitle_block_pad, TRUE,
      _pad_blocked_cb, gst_object_ref (self),
      (GDestroyNotify) gst_object_unref);

  gst_pad_set_blocked_async_full (self->video_block_pad, TRUE,
      _pad_blocked_cb, gst_object_ref (self),
      (GDestroyNotify) gst_object_unref);
  GST_SUBTITLE_OVERLAY_UNLOCK (self);

out:
  if (target)
    gst_object_unref (target);
  gst_object_unref (self);
  return ret;
}

static GstPadLinkReturn
gst_subtitle_overlay_subtitle_sink_link (GstPad * pad, GstPad * peer)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY (gst_pad_get_parent (pad));
  GstPadLinkReturn ret;
  GstCaps *caps;

  GST_DEBUG_OBJECT (pad, "Linking pad to peer %" GST_PTR_FORMAT, peer);

  caps = gst_pad_get_negotiated_caps (peer);
  if (!caps) {
    caps = gst_pad_get_caps (peer);
    if (!gst_caps_is_fixed (caps)) {
      gst_caps_unref (caps);
      caps = NULL;
    }
  }

  if (caps) {
    GST_SUBTITLE_OVERLAY_LOCK (self);
    GST_DEBUG_OBJECT (pad, "Have fixed peer caps: %" GST_PTR_FORMAT, caps);
    gst_caps_replace (&self->subcaps, caps);

    gst_pad_set_blocked_async_full (self->subtitle_block_pad, TRUE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);

    gst_pad_set_blocked_async_full (self->video_block_pad, TRUE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);
    GST_SUBTITLE_OVERLAY_UNLOCK (self);
    gst_caps_unref (caps);
  }

  ret = self->subtitle_sink_link (pad, peer);

  gst_object_unref (self);
  return ret;
}

static void
gst_subtitle_overlay_subtitle_sink_unlink (GstPad * pad)
{
  GstSubtitleOverlay *self =
      GST_SUBTITLE_OVERLAY (gst_object_ref (GST_PAD_PARENT (pad)));

  /* FIXME: Can't use gst_pad_get_parent() here because this is called with
   * the object lock from state changes
   */

  GST_DEBUG_OBJECT (pad, "Pad unlinking");
  gst_caps_replace (&self->subcaps, NULL);

  self->subtitle_sink_unlink (pad);

  GST_SUBTITLE_OVERLAY_LOCK (self);
  if (self->subtitle_block_pad)
    gst_pad_set_blocked_async_full (self->subtitle_block_pad, TRUE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);

  if (self->video_block_pad)
    gst_pad_set_blocked_async_full (self->video_block_pad, TRUE,
        _pad_blocked_cb, gst_object_ref (self),
        (GDestroyNotify) gst_object_unref);
  GST_SUBTITLE_OVERLAY_UNLOCK (self);

  gst_object_unref (self);
}

static gboolean
gst_subtitle_overlay_subtitle_sink_event (GstPad * pad, GstEvent * event)
{
  GstSubtitleOverlay *self = GST_SUBTITLE_OVERLAY (gst_pad_get_parent (pad));
  gboolean ret;
  gboolean is_newsegment = FALSE;

  if (GST_EVENT_TYPE (event) == GST_EVENT_NEWSEGMENT) {
    gboolean update;
    gdouble rate, applied_rate;
    GstFormat format;
    gint64 start, stop, position;

    GST_DEBUG_OBJECT (pad, "Newsegment event: %" GST_PTR_FORMAT,
        event->structure);
    gst_event_parse_new_segment_full (event, &update, &rate, &applied_rate,
        &format, &start, &stop, &position);

    GST_DEBUG_OBJECT (pad, "Old subtitle segment: %" GST_SEGMENT_FORMAT,
        &self->subtitle_segment);
    if (self->subtitle_segment.format != format) {
      GST_DEBUG_OBJECT (pad, "Subtitle segment format changed: %s -> %s",
          gst_format_get_name (self->subtitle_segment.format),
          gst_format_get_name (format));
      gst_segment_init (&self->subtitle_segment, format);
    }

    gst_segment_set_newsegment_full (&self->subtitle_segment, update, rate,
        applied_rate, format, start, stop, position);
    GST_DEBUG_OBJECT (pad, "New subtitle segment: %" GST_SEGMENT_FORMAT,
        &self->subtitle_segment);

    is_newsegment = TRUE;
  } else if (GST_EVENT_TYPE (event) == GST_EVENT_CUSTOM_DOWNSTREAM_OOB &&
      event->structure
      && strcmp (gst_structure_get_name (event->structure),
          "subtitleoverlay-flush-subtitle") == 0) {
    GST_DEBUG_OBJECT (pad, "Custom subtitle flush event");
    GST_SUBTITLE_OVERLAY_LOCK (self);
    self->subtitle_flush = TRUE;
    if (self->subtitle_block_pad)
      gst_pad_set_blocked_async_full (self->subtitle_block_pad, TRUE,
          _pad_blocked_cb, gst_object_ref (self),
          (GDestroyNotify) gst_object_unref);
    if (self->video_block_pad)
      gst_pad_set_blocked_async_full (self->video_block_pad, TRUE,
          _pad_blocked_cb, gst_object_ref (self),
          (GDestroyNotify) gst_object_unref);
    GST_SUBTITLE_OVERLAY_UNLOCK (self);

    gst_event_unref (event);
    event = NULL;
    ret = TRUE;
    goto out;
  }

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_FLUSH_STOP:
      GST_DEBUG_OBJECT (pad,
          "Resetting subtitle segment because of flush-stop");
      gst_segment_init (&self->subtitle_segment, GST_FORMAT_UNDEFINED);
      /* fall through */
    case GST_EVENT_FLUSH_START:
    case GST_EVENT_NEWSEGMENT:
    case GST_EVENT_EOS:
      /* Add our event marker to make sure no events from here go ever outside
       * the element, they're only interesting for our internal elements */
      event =
          GST_EVENT_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST
              (event)));
      if (!event->structure) {
        event->structure =
            gst_structure_id_empty_new (_subtitle_overlay_event_marker_id);
        gst_structure_set_parent_refcount (event->structure,
            &event->mini_object.refcount);
      }
      gst_structure_id_set (event->structure, _subtitle_overlay_event_marker_id,
          G_TYPE_BOOLEAN, TRUE, NULL);
      break;
    default:
      break;
  }

  if (is_newsegment)
    self->subtitle_segment_pending = TRUE;
  ret = self->subtitle_sink_event (pad, event);
  self->subtitle_segment_pending = FALSE;

out:
  gst_object_unref (self);
  return ret;
}

static void
gst_subtitle_overlay_init (GstSubtitleOverlay * self,
    GstSubtitleOverlayClass * klass)
{
  GstPadTemplate *templ;
  GstIterator *it;
  GstPad *proxypad = NULL;

  self->lock = g_mutex_new ();

  templ = gst_static_pad_template_get (&srctemplate);
  self->srcpad = gst_ghost_pad_new_no_target_from_template ("src", templ);
  it = gst_pad_iterate_internal_links (self->srcpad);
  if (G_UNLIKELY (!it
          || gst_iterator_next (it, (gpointer) & proxypad) != GST_ITERATOR_OK
          || proxypad == NULL)) {
    GST_ERROR_OBJECT (self, "Failed to get proxypad of srcpad");
  } else {
    self->src_proxy_event = GST_PAD_EVENTFUNC (proxypad);
    gst_pad_set_event_function (proxypad,
        GST_DEBUG_FUNCPTR (gst_subtitle_overlay_src_proxy_event));
    gst_object_unref (proxypad);
  }
  if (it)
    gst_iterator_free (it);

  gst_element_add_pad (GST_ELEMENT_CAST (self), self->srcpad);

  templ = gst_static_pad_template_get (&video_sinktemplate);
  self->video_sinkpad =
      gst_ghost_pad_new_no_target_from_template ("video_sink", templ);
  self->video_sink_event = GST_PAD_EVENTFUNC (self->video_sinkpad);
  gst_pad_set_event_function (self->video_sinkpad,
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_video_sink_event));

  proxypad = NULL;
  it = gst_pad_iterate_internal_links (self->video_sinkpad);
  if (G_UNLIKELY (!it
          || gst_iterator_next (it, (gpointer) & proxypad) != GST_ITERATOR_OK
          || proxypad == NULL)) {
    GST_ERROR_OBJECT (self,
        "Failed to get internally linked pad from video sinkpad");
  }
  if (it)
    gst_iterator_free (it);
  self->video_block_pad = proxypad;
  gst_element_add_pad (GST_ELEMENT_CAST (self), self->video_sinkpad);

  templ = gst_static_pad_template_get (&subtitle_sinktemplate);
  self->subtitle_sinkpad =
      gst_ghost_pad_new_no_target_from_template ("subtitle_sink", templ);
  self->subtitle_sink_link = GST_PAD_LINKFUNC (self->subtitle_sinkpad);
  gst_pad_set_link_function (self->subtitle_sinkpad,
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_subtitle_sink_link));
  self->subtitle_sink_unlink = GST_PAD_UNLINKFUNC (self->subtitle_sinkpad);
  gst_pad_set_unlink_function (self->subtitle_sinkpad,
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_subtitle_sink_unlink));
  self->subtitle_sink_event = GST_PAD_EVENTFUNC (self->subtitle_sinkpad);
  gst_pad_set_event_function (self->subtitle_sinkpad,
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_subtitle_sink_event));
  self->subtitle_sink_setcaps = GST_PAD_SETCAPSFUNC (self->subtitle_sinkpad);
  gst_pad_set_setcaps_function (self->subtitle_sinkpad,
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_subtitle_sink_setcaps));
  gst_pad_set_getcaps_function (self->subtitle_sinkpad,
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_subtitle_sink_getcaps));
  gst_pad_set_acceptcaps_function (self->subtitle_sinkpad,
      GST_DEBUG_FUNCPTR (gst_subtitle_overlay_subtitle_sink_acceptcaps));
  gst_pad_set_bufferalloc_function (self->subtitle_sinkpad, NULL);

  proxypad = NULL;
  it = gst_pad_iterate_internal_links (self->subtitle_sinkpad);
  if (G_UNLIKELY (!it
          || gst_iterator_next (it, (gpointer) & proxypad) != GST_ITERATOR_OK
          || proxypad == NULL)) {
    GST_ERROR_OBJECT (self,
        "Failed to get internally linked pad from subtitle sinkpad");
  }
  if (it)
    gst_iterator_free (it);
  self->subtitle_block_pad = proxypad;

  gst_element_add_pad (GST_ELEMENT_CAST (self), self->subtitle_sinkpad);
}

gboolean
gst_subtitle_overlay_plugin_init (GstPlugin * plugin)
{
  GST_DEBUG_CATEGORY_INIT (subtitle_overlay_debug, "subtitleoverlay", 0,
      "Subtitle Overlay");

  _subtitle_overlay_event_marker_id =
      g_quark_from_static_string ("gst-subtitle-overlay-event-marker");

  return gst_element_register (plugin, "subtitleoverlay", GST_RANK_NONE,
      GST_TYPE_SUBTITLE_OVERLAY);
}