ext/gsettings/gstswitchsink.c

/* GStreamer
 * Copyright (c) 2005 Ronald S. Bultje <rbultje@ronald.bitfreak.net>
 * Copyright (c) 2006 Jürg Billeter <j@bitron.ch>
 * Copyright (c) 2007 Jan Schmidt <thaytan@noraisin.net>
 *
 * 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., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

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

#include <string.h>

#include "gstswitchsink.h"

GST_DEBUG_CATEGORY_STATIC (switch_debug);
#define GST_CAT_DEFAULT switch_debug

static void gst_switch_sink_dispose (GObject * object);
static GstStateChangeReturn
gst_switch_sink_change_state (GstElement * element, GstStateChange transition);

enum
{
  PROP_0
};

GST_BOILERPLATE (GstSwitchSink, gst_switch_sink, GstBin, GST_TYPE_BIN);

static void
gst_switch_sink_base_init (gpointer klass)
{
  GST_DEBUG_CATEGORY_INIT (switch_debug, "switchsink", 0, "switchsink element");
}

static void
gst_switch_sink_class_init (GstSwitchSinkClass * klass)
{
  GObjectClass *oklass = G_OBJECT_CLASS (klass);
  GstElementClass *eklass = GST_ELEMENT_CLASS (klass);
  static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
      GST_PAD_SINK,
      GST_PAD_ALWAYS,
      GST_STATIC_CAPS_ANY);
  GstPadTemplate *child_pad_templ;

  oklass->dispose = gst_switch_sink_dispose;
  eklass->change_state = gst_switch_sink_change_state;

  /* Provide a default pad template if the child didn't */
  child_pad_templ = gst_element_class_get_pad_template (eklass, "sink");
  if (child_pad_templ == NULL) {
    gst_element_class_add_pad_template (eklass,
        gst_static_pad_template_get (&sink_template));
  }
}

static gboolean
gst_switch_sink_reset (GstSwitchSink * sink)
{
  /* this will install fakesink if no other child has been set,
   * otherwise we rely on the subclass to know when to unset its
   * custom kid */
  if (sink->kid == NULL) {
    return gst_switch_sink_set_child (sink, NULL);
  }

  return TRUE;
}

static void
gst_switch_sink_init (GstSwitchSink * sink, GstSwitchSinkClass * g_class)
{
  GstElementClass *eklass = GST_ELEMENT_GET_CLASS (sink);
  GstPadTemplate *templ;

  templ = gst_element_class_get_pad_template (eklass, "sink");
  sink->pad = gst_ghost_pad_new_no_target_from_template ("sink", templ);
  gst_element_add_pad (GST_ELEMENT (sink), sink->pad);

  gst_switch_sink_reset (sink);

  GST_OBJECT_FLAG_SET (sink, GST_ELEMENT_IS_SINK);
}

static void
gst_switch_sink_dispose (GObject * object)
{
  GstSwitchSink *sink = GST_SWITCH_SINK (object);
  GstObject *new_kid, *kid;

  GST_OBJECT_LOCK (sink);
  new_kid = GST_OBJECT_CAST (sink->new_kid);
  sink->new_kid = NULL;

  kid = GST_OBJECT_CAST (sink->kid);
  sink->kid = NULL;
  GST_OBJECT_UNLOCK (sink);

  gst_object_replace (&new_kid, NULL);
  gst_object_replace (&kid, NULL);

  GST_CALL_PARENT (G_OBJECT_CLASS, dispose, (object));
}

static gboolean
gst_switch_sink_commit_new_kid (GstSwitchSink * sink)
{
  GstPad *targetpad;
  GstState kid_state;
  GstElement *new_kid, *old_kid;
  gboolean is_fakesink = FALSE;
  GstBus *bus;

  /* need locking around member accesses */
  GST_OBJECT_LOCK (sink);
  /* If we're currently changing state, set the child to the next state
   * we're transitioning too, rather than our current state which is 
   * about to change */
  if (GST_STATE_NEXT (sink) != GST_STATE_VOID_PENDING)
    kid_state = GST_STATE_NEXT (sink);
  else
    kid_state = GST_STATE (sink);

  new_kid = sink->new_kid ? gst_object_ref (sink->new_kid) : NULL;
  sink->new_kid = NULL;
  GST_OBJECT_UNLOCK (sink);

  /* Fakesink by default if NULL is passed as the new child */
  if (new_kid == NULL) {
    GST_DEBUG_OBJECT (sink, "Replacing kid with fakesink");
    new_kid = gst_element_factory_make ("fakesink", "testsink");
    if (new_kid == NULL) {
      GST_ERROR_OBJECT (sink, "Failed to create fakesink");
      return FALSE;
    }
    /* Add a reference, as it would if the element came from sink->new_kid */
    gst_object_ref (new_kid);
    g_object_set (new_kid, "sync", TRUE, NULL);
    is_fakesink = TRUE;
  } else {
    GST_DEBUG_OBJECT (sink, "Setting new kid");
  }

  /* set temporary bus of our own to catch error messages from the child
   * (could we just set our own bus on it, or would the state change messages
   * from the not-yet-added element confuse the state change algorithm? Let's
   * play it safe for now) */
  bus = gst_bus_new ();
  gst_element_set_bus (new_kid, bus);
  gst_object_unref (bus);

  if (gst_element_set_state (new_kid, kid_state) == GST_STATE_CHANGE_FAILURE) {
    GstMessage *msg;

    /* check if child posted an error message and if so re-post it on our bus
     * so that the application gets to see a decent error and not our generic
     * fallback error message which is completely indecipherable to the user */
    msg = gst_bus_pop_filtered (GST_ELEMENT_BUS (new_kid), GST_MESSAGE_ERROR);
    if (msg) {
      GST_INFO_OBJECT (sink, "Forwarding kid error: %" GST_PTR_FORMAT, msg);
      gst_element_post_message (GST_ELEMENT (sink), msg);
    }
    GST_ELEMENT_ERROR (sink, CORE, STATE_CHANGE, (NULL),
        ("Failed to set state on new child."));
    gst_element_set_bus (new_kid, NULL);
    gst_object_unref (new_kid);
    return FALSE;
  }
  gst_element_set_bus (new_kid, NULL);
  gst_bin_add (GST_BIN (sink), new_kid);

  /* Now, replace the existing child */
  GST_OBJECT_LOCK (sink);
  old_kid = sink->kid;
  sink->kid = new_kid;
  /* Mark whether a custom kid or fakesink has been installed */
  sink->have_kid = !is_fakesink;
  GST_OBJECT_UNLOCK (sink);

  /* kill old element */
  if (old_kid) {
    GST_DEBUG_OBJECT (sink, "Removing old kid %" GST_PTR_FORMAT, old_kid);
    gst_element_set_state (old_kid, GST_STATE_NULL);
    gst_bin_remove (GST_BIN (sink), old_kid);
    gst_object_unref (old_kid);
    /* Don't lose the SINK flag */
    GST_OBJECT_FLAG_SET (sink, GST_ELEMENT_IS_SINK);
  }

  /* re-attach ghostpad */
  GST_DEBUG_OBJECT (sink, "Creating new ghostpad");
  targetpad = gst_element_get_static_pad (sink->kid, "sink");
  gst_ghost_pad_set_target (GST_GHOST_PAD (sink->pad), targetpad);
  gst_object_unref (targetpad);
  GST_DEBUG_OBJECT (sink, "done changing child of switchsink");

  /* FIXME: Push new-segment info and pre-roll buffer(s) into the kid */

  return TRUE;
}

gboolean
gst_switch_sink_set_child (GstSwitchSink * sink, GstElement * new_kid)
{
  GstState cur, next;
  GstElement **p_kid;

  /* Nothing to do if clearing the child and we've already installed fakesink */
  if (new_kid == NULL && sink->kid != NULL && sink->have_kid == FALSE)
    return TRUE;

  /* Store the new kid to be committed later */
  GST_OBJECT_LOCK (sink);
  cur = GST_STATE (sink);
  next = GST_STATE_NEXT (sink);
  p_kid = &sink->new_kid;
  gst_object_replace ((GstObject **) p_kid, (GstObject *) new_kid);
  GST_OBJECT_UNLOCK (sink);
  if (new_kid)
    gst_object_unref (new_kid);

  /* Sometime, it would be lovely to allow sink changes even when
   * already running, but this involves sending an appropriate new-segment
   * and possibly prerolling etc */
  /* FIXME: Block the pad and replace the kid when it completes */
  if (cur > GST_STATE_READY || next == GST_STATE_PAUSED) {
    GST_DEBUG_OBJECT (sink,
        "Switch-sink is already running. Ignoring change of child.");
    gst_object_unref (new_kid);
    return TRUE;
  }

  return gst_switch_sink_commit_new_kid (sink);
}

static GstStateChangeReturn
gst_switch_sink_change_state (GstElement * element, GstStateChange transition)
{
  GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
  GstSwitchSink *sink = GST_SWITCH_SINK (element);

  ret = GST_CALL_PARENT_WITH_DEFAULT (GST_ELEMENT_CLASS, change_state,
      (element, transition), GST_STATE_CHANGE_SUCCESS);

  switch (transition) {
    case GST_STATE_CHANGE_READY_TO_NULL:
      if (!gst_switch_sink_reset (sink))
        ret = GST_STATE_CHANGE_FAILURE;
      break;
    default:
      break;
  }

  return ret;
}