ext/gl/gstglbasemixer.c - imx-gst-plugins-base - Git at Google

 /* Generic video mixer plugin
  *
  * GStreamer
  * Copyright (C) 2015 Matthew Waters <matthew@centricular.com>
  *
  * 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 <gst/gst.h>
 #include <gst/video/video.h>

 #include "gstglbasemixer.h"

 #define gst_gl_base_mixer_parent_class parent_class
 G_DEFINE_ABSTRACT_TYPE (GstGLBaseMixer, gst_gl_base_mixer,
     GST_TYPE_VIDEO_AGGREGATOR);

 #define GST_CAT_DEFAULT gst_gl_base_mixer_debug
 GST_DEBUG_CATEGORY (gst_gl_base_mixer_debug);

 static void gst_gl_base_mixer_pad_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec);
 static void gst_gl_base_mixer_pad_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec);

 static void gst_gl_base_mixer_set_context (GstElement * element,
     GstContext * context);
 static GstStateChangeReturn gst_gl_base_mixer_change_state (GstElement *
     element, GstStateChange transition);

 enum
 {
   PROP_PAD_0
 };

 #define GST_GL_BASE_MIXER_GET_PRIVATE(obj)  \
     (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_GL_BASE_MIXER, GstGLBaseMixerPrivate))

 struct _GstGLBaseMixerPrivate
 {
   gboolean negotiated;

   GstGLContext *other_context;
 };

 G_DEFINE_TYPE (GstGLBaseMixerPad, gst_gl_base_mixer_pad,
     GST_TYPE_VIDEO_AGGREGATOR_PAD);

 static void
 gst_gl_base_mixer_pad_class_init (GstGLBaseMixerPadClass * klass)
 {
   GObjectClass *gobject_class = (GObjectClass *) klass;
   GstVideoAggregatorPadClass *vaggpad_class =
       (GstVideoAggregatorPadClass *) klass;

   gobject_class->set_property = gst_gl_base_mixer_pad_set_property;
   gobject_class->get_property = gst_gl_base_mixer_pad_get_property;

   vaggpad_class->set_info = NULL;
   vaggpad_class->prepare_frame = NULL;
   vaggpad_class->clean_frame = NULL;
 }

 static void
 gst_gl_base_mixer_pad_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec)
 {
   switch (prop_id) {
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 static void
 gst_gl_base_mixer_pad_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec)
 {
   switch (prop_id) {
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }


 static gboolean
 _find_local_gl_context (GstGLBaseMixer * mix)
 {
   if (gst_gl_query_local_gl_context (GST_ELEMENT (mix), GST_PAD_SRC,
           &mix->context))
     return TRUE;
   if (gst_gl_query_local_gl_context (GST_ELEMENT (mix), GST_PAD_SINK,
           &mix->context))
     return TRUE;
   return FALSE;
 }

 static gboolean
 _get_gl_context (GstGLBaseMixer * mix)
 {
   GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);
   GError *error = NULL;

   if (!gst_gl_ensure_element_data (mix, &mix->display,
           &mix->priv->other_context))
     return FALSE;

   gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);

   _find_local_gl_context (mix);

   GST_OBJECT_LOCK (mix->display);
   if (!mix->context) {
     do {
       if (mix->context) {
         gst_object_unref (mix->context);
         mix->context = NULL;
       }
       /* just get a GL context.  we don't care */
       mix->context =
           gst_gl_display_get_gl_context_for_thread (mix->display, NULL);
       if (!mix->context) {
         if (!gst_gl_display_create_context (mix->display,
                 mix->priv->other_context, &mix->context, &error)) {
           GST_OBJECT_UNLOCK (mix->display);
           goto context_error;
         }
       }
     } while (!gst_gl_display_add_context (mix->display, mix->context));
   }
   GST_OBJECT_UNLOCK (mix->display);

   {
     GstGLAPI current_gl_api = gst_gl_context_get_gl_api (mix->context);
     if ((current_gl_api & mix_class->supported_gl_api) == 0)
       goto unsupported_gl_api;
   }

   return TRUE;

 unsupported_gl_api:
   {
     GstGLAPI gl_api = gst_gl_context_get_gl_api (mix->context);
     gchar *gl_api_str = gst_gl_api_to_string (gl_api);
     gchar *supported_gl_api_str =
         gst_gl_api_to_string (mix_class->supported_gl_api);
     GST_ELEMENT_ERROR (mix, RESOURCE, BUSY,
         ("GL API's not compatible context: %s supported: %s", gl_api_str,
             supported_gl_api_str), (NULL));

     g_free (supported_gl_api_str);
     g_free (gl_api_str);
     return FALSE;
   }
 context_error:
   {
     GST_ELEMENT_ERROR (mix, RESOURCE, NOT_FOUND, ("%s", error->message),
         (NULL));
     g_clear_error (&error);
     return FALSE;
   }
 }

 static gboolean
 gst_gl_base_mixer_propose_allocation (GstAggregator * agg,
     GstAggregatorPad * aggpad, GstQuery * decide_query, GstQuery * query)
 {
   GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

   if (!_get_gl_context (mix))
     return FALSE;

   return TRUE;
 }

 static gboolean
 gst_gl_base_mixer_sink_query (GstAggregator * agg, GstAggregatorPad * bpad,
     GstQuery * query)
 {
   GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

   GST_TRACE ("QUERY %" GST_PTR_FORMAT, query);

   switch (GST_QUERY_TYPE (query)) {
     case GST_QUERY_CONTEXT:
     {
       if (gst_gl_handle_context_query ((GstElement *) mix, query,
               mix->display, mix->context, mix->priv->other_context))
         return TRUE;
       break;
     }
     default:
       break;
   }

   return GST_AGGREGATOR_CLASS (parent_class)->sink_query (agg, bpad, query);;
 }

 static void
 gst_gl_base_mixer_pad_init (GstGLBaseMixerPad * mixerpad)
 {
 }

 /* GLBaseMixer signals and args */
 enum
 {
   /* FILL ME */
   LAST_SIGNAL
 };

 enum
 {
   PROP_0,
   PROP_CONTEXT
 };

 static gboolean gst_gl_base_mixer_src_query (GstAggregator * agg,
     GstQuery * query);

 static gboolean
 gst_gl_base_mixer_src_activate_mode (GstAggregator * aggregator,
     GstPadMode mode, gboolean active);
 static gboolean gst_gl_base_mixer_stop (GstAggregator * agg);
 static gboolean gst_gl_base_mixer_start (GstAggregator * agg);

 static void gst_gl_base_mixer_set_property (GObject * object, guint prop_id,
     const GValue * value, GParamSpec * pspec);
 static void gst_gl_base_mixer_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec);

 static gboolean gst_gl_base_mixer_decide_allocation (GstAggregator * agg,
     GstQuery * query);

 static void
 gst_gl_base_mixer_class_init (GstGLBaseMixerClass * klass)
 {
   GObjectClass *gobject_class;
   GstElementClass *element_class;
   GstAggregatorClass *agg_class = (GstAggregatorClass *) klass;

   GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "glmixer", 0, "opengl mixer");

   gobject_class = (GObjectClass *) klass;
   element_class = GST_ELEMENT_CLASS (klass);

   g_type_class_add_private (klass, sizeof (GstGLBaseMixerPrivate));

   gobject_class->get_property = gst_gl_base_mixer_get_property;
   gobject_class->set_property = gst_gl_base_mixer_set_property;

   element_class->set_context =
       GST_DEBUG_FUNCPTR (gst_gl_base_mixer_set_context);
   element_class->change_state = gst_gl_base_mixer_change_state;

   agg_class->sink_query = gst_gl_base_mixer_sink_query;
   agg_class->src_query = gst_gl_base_mixer_src_query;
   agg_class->src_activate = gst_gl_base_mixer_src_activate_mode;
   agg_class->stop = gst_gl_base_mixer_stop;
   agg_class->start = gst_gl_base_mixer_start;
   agg_class->decide_allocation = gst_gl_base_mixer_decide_allocation;
   agg_class->propose_allocation = gst_gl_base_mixer_propose_allocation;

   g_object_class_install_property (gobject_class, PROP_CONTEXT,
       g_param_spec_object ("context",
           "OpenGL context",
           "Get OpenGL context",
           GST_TYPE_GL_CONTEXT, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));

   /* Register the pad class */
   g_type_class_ref (GST_TYPE_GL_BASE_MIXER_PAD);

   klass->supported_gl_api = GST_GL_API_ANY;
 }

 static void
 gst_gl_base_mixer_init (GstGLBaseMixer * mix)
 {
   mix->priv = GST_GL_BASE_MIXER_GET_PRIVATE (mix);
 }

 static void
 gst_gl_base_mixer_set_context (GstElement * element, GstContext * context)
 {
   GstGLBaseMixer *mix = GST_GL_BASE_MIXER (element);
   GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);

   gst_gl_handle_set_context (element, context, &mix->display,
       &mix->priv->other_context);

   if (mix->display)
     gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);

   GST_ELEMENT_CLASS (parent_class)->set_context (element, context);
 }

 static gboolean
 gst_gl_base_mixer_activate (GstGLBaseMixer * mix, gboolean active)
 {
   GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);
   gboolean result = TRUE;

   if (active) {
     if (!gst_gl_ensure_element_data (mix, &mix->display,
             &mix->priv->other_context))
       return FALSE;

     gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);
   }

   return result;
 }

 static gboolean
 gst_gl_base_mixer_src_activate_mode (GstAggregator * aggregator,
     GstPadMode mode, gboolean active)
 {
   GstGLBaseMixer *mix;
   gboolean result = FALSE;

   mix = GST_GL_BASE_MIXER (aggregator);

   switch (mode) {
     case GST_PAD_MODE_PUSH:
     case GST_PAD_MODE_PULL:
       result = gst_gl_base_mixer_activate (mix, active);
       break;
     default:
       result = TRUE;
       break;
   }
   return result;
 }

 static gboolean
 gst_gl_base_mixer_src_query (GstAggregator * agg, GstQuery * query)
 {
   GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

   switch (GST_QUERY_TYPE (query)) {
     case GST_QUERY_CONTEXT:
     {
       if (gst_gl_handle_context_query ((GstElement *) mix, query,
               mix->display, mix->context, mix->priv->other_context))
         return TRUE;
       break;
     }
     default:
       break;
   }

   return GST_AGGREGATOR_CLASS (parent_class)->src_query (agg, query);
 }

 static gboolean
 gst_gl_base_mixer_decide_allocation (GstAggregator * agg, GstQuery * query)
 {
   GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

   if (!_get_gl_context (mix))
     return FALSE;

   return TRUE;
 }

 static void
 gst_gl_base_mixer_get_property (GObject * object,
     guint prop_id, GValue * value, GParamSpec * pspec)
 {
   GstGLBaseMixer *mixer = GST_GL_BASE_MIXER (object);

   switch (prop_id) {
     case PROP_CONTEXT:
       g_value_set_object (value, mixer->context);
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 static void
 gst_gl_base_mixer_set_property (GObject * object,
     guint prop_id, const GValue * value, GParamSpec * pspec)
 {
   switch (prop_id) {
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }

 static gboolean
 gst_gl_base_mixer_start (GstAggregator * agg)
 {
   return GST_AGGREGATOR_CLASS (parent_class)->start (agg);;
 }

 static gboolean
 gst_gl_base_mixer_stop (GstAggregator * agg)
 {
   GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

   if (mix->context) {
     gst_object_unref (mix->context);
     mix->context = NULL;
   }

   return TRUE;
 }

 static GstStateChangeReturn
 gst_gl_base_mixer_change_state (GstElement * element, GstStateChange transition)
 {
   GstGLBaseMixer *mix = GST_GL_BASE_MIXER (element);
   GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);
   GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;

   GST_DEBUG_OBJECT (mix, "changing state: %s => %s",
       gst_element_state_get_name (GST_STATE_TRANSITION_CURRENT (transition)),
       gst_element_state_get_name (GST_STATE_TRANSITION_NEXT (transition)));

   switch (transition) {
     case GST_STATE_CHANGE_NULL_TO_READY:
       if (!gst_gl_ensure_element_data (element, &mix->display,
               &mix->priv->other_context))
         return GST_STATE_CHANGE_FAILURE;

       gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);
       break;
     default:
       break;
   }

   ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
   if (ret == GST_STATE_CHANGE_FAILURE)
     return ret;

   switch (transition) {
     case GST_STATE_CHANGE_READY_TO_NULL:
       if (mix->priv->other_context) {
         gst_object_unref (mix->priv->other_context);
         mix->priv->other_context = NULL;
       }

       if (mix->display) {
         gst_object_unref (mix->display);
         mix->display = NULL;
       }
       break;
     default:
       break;
   }

   return ret;
 }
	/* Generic video mixer plugin
	*
	* GStreamer
	* Copyright (C) 2015 Matthew Waters <matthew@centricular.com>
	*
	* 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 <gst/gst.h>
	#include <gst/video/video.h>

	#include "gstglbasemixer.h"

	#define gst_gl_base_mixer_parent_class parent_class
	G_DEFINE_ABSTRACT_TYPE (GstGLBaseMixer, gst_gl_base_mixer,
	GST_TYPE_VIDEO_AGGREGATOR);

	#define GST_CAT_DEFAULT gst_gl_base_mixer_debug
	GST_DEBUG_CATEGORY (gst_gl_base_mixer_debug);

	static void gst_gl_base_mixer_pad_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec);
	static void gst_gl_base_mixer_pad_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec);

	static void gst_gl_base_mixer_set_context (GstElement * element,
	GstContext * context);
	static GstStateChangeReturn gst_gl_base_mixer_change_state (GstElement *
	element, GstStateChange transition);

	enum
	{
	PROP_PAD_0
	};

	#define GST_GL_BASE_MIXER_GET_PRIVATE(obj) \
	(G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_GL_BASE_MIXER, GstGLBaseMixerPrivate))

	struct _GstGLBaseMixerPrivate
	{
	gboolean negotiated;

	GstGLContext *other_context;
	};

	G_DEFINE_TYPE (GstGLBaseMixerPad, gst_gl_base_mixer_pad,
	GST_TYPE_VIDEO_AGGREGATOR_PAD);

	static void
	gst_gl_base_mixer_pad_class_init (GstGLBaseMixerPadClass * klass)
	{
	GObjectClass gobject_class = (GObjectClass ) klass;
	GstVideoAggregatorPadClass *vaggpad_class =
	(GstVideoAggregatorPadClass *) klass;

	gobject_class->set_property = gst_gl_base_mixer_pad_set_property;
	gobject_class->get_property = gst_gl_base_mixer_pad_get_property;

	vaggpad_class->set_info = NULL;
	vaggpad_class->prepare_frame = NULL;
	vaggpad_class->clean_frame = NULL;
	}

	static void
	gst_gl_base_mixer_pad_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec)
	{
	switch (prop_id) {
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	static void
	gst_gl_base_mixer_pad_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec)
	{
	switch (prop_id) {
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}


	static gboolean
	_find_local_gl_context (GstGLBaseMixer * mix)
	{
	if (gst_gl_query_local_gl_context (GST_ELEMENT (mix), GST_PAD_SRC,
	&mix->context))
	return TRUE;
	if (gst_gl_query_local_gl_context (GST_ELEMENT (mix), GST_PAD_SINK,
	&mix->context))
	return TRUE;
	return FALSE;
	}

	static gboolean
	_get_gl_context (GstGLBaseMixer * mix)
	{
	GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);
	GError *error = NULL;

	if (!gst_gl_ensure_element_data (mix, &mix->display,
	&mix->priv->other_context))
	return FALSE;

	gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);

	_find_local_gl_context (mix);

	GST_OBJECT_LOCK (mix->display);
	if (!mix->context) {
	do {
	if (mix->context) {
	gst_object_unref (mix->context);
	mix->context = NULL;
	}
	/* just get a GL context. we don't care */
	mix->context =
	gst_gl_display_get_gl_context_for_thread (mix->display, NULL);
	if (!mix->context) {
	if (!gst_gl_display_create_context (mix->display,
	mix->priv->other_context, &mix->context, &error)) {
	GST_OBJECT_UNLOCK (mix->display);
	goto context_error;
	}
	}
	} while (!gst_gl_display_add_context (mix->display, mix->context));
	}
	GST_OBJECT_UNLOCK (mix->display);

	{
	GstGLAPI current_gl_api = gst_gl_context_get_gl_api (mix->context);
	if ((current_gl_api & mix_class->supported_gl_api) == 0)
	goto unsupported_gl_api;
	}

	return TRUE;

	unsupported_gl_api:
	{
	GstGLAPI gl_api = gst_gl_context_get_gl_api (mix->context);
	gchar *gl_api_str = gst_gl_api_to_string (gl_api);
	gchar *supported_gl_api_str =
	gst_gl_api_to_string (mix_class->supported_gl_api);
	GST_ELEMENT_ERROR (mix, RESOURCE, BUSY,
	("GL API's not compatible context: %s supported: %s", gl_api_str,
	supported_gl_api_str), (NULL));

	g_free (supported_gl_api_str);
	g_free (gl_api_str);
	return FALSE;
	}
	context_error:
	{
	GST_ELEMENT_ERROR (mix, RESOURCE, NOT_FOUND, ("%s", error->message),
	(NULL));
	g_clear_error (&error);
	return FALSE;
	}
	}

	static gboolean
	gst_gl_base_mixer_propose_allocation (GstAggregator * agg,
	GstAggregatorPad * aggpad, GstQuery * decide_query, GstQuery * query)
	{
	GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

	if (!_get_gl_context (mix))
	return FALSE;

	return TRUE;
	}

	static gboolean
	gst_gl_base_mixer_sink_query (GstAggregator * agg, GstAggregatorPad * bpad,
	GstQuery * query)
	{
	GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

	GST_TRACE ("QUERY %" GST_PTR_FORMAT, query);

	switch (GST_QUERY_TYPE (query)) {
	case GST_QUERY_CONTEXT:
	{
	if (gst_gl_handle_context_query ((GstElement *) mix, query,
	mix->display, mix->context, mix->priv->other_context))
	return TRUE;
	break;
	}
	default:
	break;
	}

	return GST_AGGREGATOR_CLASS (parent_class)->sink_query (agg, bpad, query);;
	}

	static void
	gst_gl_base_mixer_pad_init (GstGLBaseMixerPad * mixerpad)
	{
	}

	/* GLBaseMixer signals and args */
	enum
	{
	/* FILL ME */
	LAST_SIGNAL
	};

	enum
	{
	PROP_0,
	PROP_CONTEXT
	};

	static gboolean gst_gl_base_mixer_src_query (GstAggregator * agg,
	GstQuery * query);

	static gboolean
	gst_gl_base_mixer_src_activate_mode (GstAggregator * aggregator,
	GstPadMode mode, gboolean active);
	static gboolean gst_gl_base_mixer_stop (GstAggregator * agg);
	static gboolean gst_gl_base_mixer_start (GstAggregator * agg);

	static void gst_gl_base_mixer_set_property (GObject * object, guint prop_id,
	const GValue * value, GParamSpec * pspec);
	static void gst_gl_base_mixer_get_property (GObject * object, guint prop_id,
	GValue * value, GParamSpec * pspec);

	static gboolean gst_gl_base_mixer_decide_allocation (GstAggregator * agg,
	GstQuery * query);

	static void
	gst_gl_base_mixer_class_init (GstGLBaseMixerClass * klass)
	{
	GObjectClass *gobject_class;
	GstElementClass *element_class;
	GstAggregatorClass agg_class = (GstAggregatorClass ) klass;

	GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "glmixer", 0, "opengl mixer");

	gobject_class = (GObjectClass *) klass;
	element_class = GST_ELEMENT_CLASS (klass);

	g_type_class_add_private (klass, sizeof (GstGLBaseMixerPrivate));

	gobject_class->get_property = gst_gl_base_mixer_get_property;
	gobject_class->set_property = gst_gl_base_mixer_set_property;

	element_class->set_context =
	GST_DEBUG_FUNCPTR (gst_gl_base_mixer_set_context);
	element_class->change_state = gst_gl_base_mixer_change_state;

	agg_class->sink_query = gst_gl_base_mixer_sink_query;
	agg_class->src_query = gst_gl_base_mixer_src_query;
	agg_class->src_activate = gst_gl_base_mixer_src_activate_mode;
	agg_class->stop = gst_gl_base_mixer_stop;
	agg_class->start = gst_gl_base_mixer_start;
	agg_class->decide_allocation = gst_gl_base_mixer_decide_allocation;
	agg_class->propose_allocation = gst_gl_base_mixer_propose_allocation;

	g_object_class_install_property (gobject_class, PROP_CONTEXT,
	g_param_spec_object ("context",
	"OpenGL context",
	"Get OpenGL context",
	GST_TYPE_GL_CONTEXT, G_PARAM_READABLE \| G_PARAM_STATIC_STRINGS));

	/* Register the pad class */
	g_type_class_ref (GST_TYPE_GL_BASE_MIXER_PAD);

	klass->supported_gl_api = GST_GL_API_ANY;
	}

	static void
	gst_gl_base_mixer_init (GstGLBaseMixer * mix)
	{
	mix->priv = GST_GL_BASE_MIXER_GET_PRIVATE (mix);
	}

	static void
	gst_gl_base_mixer_set_context (GstElement * element, GstContext * context)
	{
	GstGLBaseMixer *mix = GST_GL_BASE_MIXER (element);
	GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);

	gst_gl_handle_set_context (element, context, &mix->display,
	&mix->priv->other_context);

	if (mix->display)
	gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);

	GST_ELEMENT_CLASS (parent_class)->set_context (element, context);
	}

	static gboolean
	gst_gl_base_mixer_activate (GstGLBaseMixer * mix, gboolean active)
	{
	GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);
	gboolean result = TRUE;

	if (active) {
	if (!gst_gl_ensure_element_data (mix, &mix->display,
	&mix->priv->other_context))
	return FALSE;

	gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);
	}

	return result;
	}

	static gboolean
	gst_gl_base_mixer_src_activate_mode (GstAggregator * aggregator,
	GstPadMode mode, gboolean active)
	{
	GstGLBaseMixer *mix;
	gboolean result = FALSE;

	mix = GST_GL_BASE_MIXER (aggregator);

	switch (mode) {
	case GST_PAD_MODE_PUSH:
	case GST_PAD_MODE_PULL:
	result = gst_gl_base_mixer_activate (mix, active);
	break;
	default:
	result = TRUE;
	break;
	}
	return result;
	}

	static gboolean
	gst_gl_base_mixer_src_query (GstAggregator * agg, GstQuery * query)
	{
	GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

	switch (GST_QUERY_TYPE (query)) {
	case GST_QUERY_CONTEXT:
	{
	if (gst_gl_handle_context_query ((GstElement *) mix, query,
	mix->display, mix->context, mix->priv->other_context))
	return TRUE;
	break;
	}
	default:
	break;
	}

	return GST_AGGREGATOR_CLASS (parent_class)->src_query (agg, query);
	}

	static gboolean
	gst_gl_base_mixer_decide_allocation (GstAggregator * agg, GstQuery * query)
	{
	GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

	if (!_get_gl_context (mix))
	return FALSE;

	return TRUE;
	}

	static void
	gst_gl_base_mixer_get_property (GObject * object,
	guint prop_id, GValue * value, GParamSpec * pspec)
	{
	GstGLBaseMixer *mixer = GST_GL_BASE_MIXER (object);

	switch (prop_id) {
	case PROP_CONTEXT:
	g_value_set_object (value, mixer->context);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	static void
	gst_gl_base_mixer_set_property (GObject * object,
	guint prop_id, const GValue * value, GParamSpec * pspec)
	{
	switch (prop_id) {
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
	break;
	}
	}

	static gboolean
	gst_gl_base_mixer_start (GstAggregator * agg)
	{
	return GST_AGGREGATOR_CLASS (parent_class)->start (agg);;
	}

	static gboolean
	gst_gl_base_mixer_stop (GstAggregator * agg)
	{
	GstGLBaseMixer *mix = GST_GL_BASE_MIXER (agg);

	if (mix->context) {
	gst_object_unref (mix->context);
	mix->context = NULL;
	}

	return TRUE;
	}

	static GstStateChangeReturn
	gst_gl_base_mixer_change_state (GstElement * element, GstStateChange transition)
	{
	GstGLBaseMixer *mix = GST_GL_BASE_MIXER (element);
	GstGLBaseMixerClass *mix_class = GST_GL_BASE_MIXER_GET_CLASS (mix);
	GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;

	GST_DEBUG_OBJECT (mix, "changing state: %s => %s",
	gst_element_state_get_name (GST_STATE_TRANSITION_CURRENT (transition)),
	gst_element_state_get_name (GST_STATE_TRANSITION_NEXT (transition)));

	switch (transition) {
	case GST_STATE_CHANGE_NULL_TO_READY:
	if (!gst_gl_ensure_element_data (element, &mix->display,
	&mix->priv->other_context))
	return GST_STATE_CHANGE_FAILURE;

	gst_gl_display_filter_gl_api (mix->display, mix_class->supported_gl_api);
	break;
	default:
	break;
	}

	ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
	if (ret == GST_STATE_CHANGE_FAILURE)
	return ret;

	switch (transition) {
	case GST_STATE_CHANGE_READY_TO_NULL:
	if (mix->priv->other_context) {
	gst_object_unref (mix->priv->other_context);
	mix->priv->other_context = NULL;
	}

	if (mix->display) {
	gst_object_unref (mix->display);
	mix->display = NULL;
	}
	break;
	default:
	break;
	}

	return ret;
	}