Source/WebCore/platform/graphics/gstreamer/TextCombinerGStreamer.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2013 Cable Television Laboratories, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "TextCombinerGStreamer.h"

 #if ENABLE(VIDEO) && USE(GSTREAMER)

 #include "GStreamerCommon.h"

 static GstStaticPadTemplate sinkTemplate =
     GST_STATIC_PAD_TEMPLATE("sink_%u", GST_PAD_SINK, GST_PAD_REQUEST,
         GST_STATIC_CAPS_ANY);

 static GstStaticPadTemplate srcTemplate =
     GST_STATIC_PAD_TEMPLATE("src", GST_PAD_SRC, GST_PAD_ALWAYS,
         GST_STATIC_CAPS_ANY);

 GST_DEBUG_CATEGORY_STATIC(webkitTextCombinerDebug);
 #define GST_CAT_DEFAULT webkitTextCombinerDebug

 #define webkit_text_combiner_parent_class parent_class
 G_DEFINE_TYPE_WITH_CODE(WebKitTextCombiner, webkit_text_combiner, GST_TYPE_BIN,
     GST_DEBUG_CATEGORY_INIT(webkitTextCombinerDebug, "webkittextcombiner", 0,
         "webkit text combiner"));

 enum {
     PROP_PAD_0,
     PROP_PAD_TAGS
 };

 #define WEBKIT_TYPE_TEXT_COMBINER_PAD webkit_text_combiner_pad_get_type()

 #define WEBKIT_TEXT_COMBINER_PAD(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj), WEBKIT_TYPE_TEXT_COMBINER_PAD, WebKitTextCombinerPad))
 #define WEBKIT_TEXT_COMBINER_PAD_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass), WEBKIT_TYPE_TEXT_COMBINER_PAD, WebKitTextCombinerPadClass))
 #define WEBKIT_IS_TEXT_COMBINER_PAD(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj), WEBKIT_TYPE_TEXT_COMBINER_PAD))
 #define WEBKIT_IS_TEXT_COMBINER_PAD_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass), WEBKIT_TYPE_TEXT_COMBINER_PAD))
 #define WEBKIT_TEXT_COMBINER_PAD_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS((obj), WEBKIT_TYPE_TEXT_COMBINER_PAD, WebKitTextCombinerPadClass))

 typedef struct _WebKitTextCombinerPad WebKitTextCombinerPad;
 typedef struct _WebKitTextCombinerPadClass WebKitTextCombinerPadClass;

 struct _WebKitTextCombinerPad {
     GstGhostPad parent;

     GstTagList* tags;
     GstPad* funnelPad;
 };

 struct _WebKitTextCombinerPadClass {
     GstGhostPadClass parent;
 };

 G_DEFINE_TYPE(WebKitTextCombinerPad, webkit_text_combiner_pad, GST_TYPE_GHOST_PAD);

 static GType webVTTEncType;

 static gboolean webkitTextCombinerPadEvent(GstPad*, GstObject* parent, GstEvent*);

 static void webkit_text_combiner_init(WebKitTextCombiner* combiner)
 {
     combiner->funnel = gst_element_factory_make("funnel", nullptr);
     ASSERT(combiner->funnel);

     gboolean ret = gst_bin_add(GST_BIN(combiner), combiner->funnel);
     UNUSED_PARAM(ret);
     ASSERT(ret);

     GRefPtr<GstPad> pad = adoptGRef(gst_element_get_static_pad(combiner->funnel, "src"));
     ASSERT(pad);

     ret = gst_element_add_pad(GST_ELEMENT(combiner), gst_ghost_pad_new("src", pad.get()));
     ASSERT(ret);
 }

 static void webkit_text_combiner_pad_init(WebKitTextCombinerPad* pad)
 {
     gst_pad_set_event_function(GST_PAD(pad), webkitTextCombinerPadEvent);
 }

 static void webkitTextCombinerPadDispose(GObject* object)
 {
     WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(object);
     g_clear_pointer(&combinerPad->tags, gst_tag_list_unref);
     g_clear_pointer(&combinerPad->funnelPad, gst_object_unref);
     G_OBJECT_CLASS(webkit_text_combiner_pad_parent_class)->dispose(object);
 }

 static void webkitTextCombinerPadGetProperty(GObject* object, guint propertyId, GValue* value, GParamSpec* pspec)
 {
     WebKitTextCombinerPad* pad = WEBKIT_TEXT_COMBINER_PAD(object);
     switch (propertyId) {
     case PROP_PAD_TAGS:
         GST_OBJECT_LOCK(object);
         if (pad->tags)
             g_value_take_boxed(value, gst_tag_list_copy(pad->tags));
         GST_OBJECT_UNLOCK(object);
         break;
     default:
         G_OBJECT_WARN_INVALID_PROPERTY_ID(object, propertyId, pspec);
         break;
     }
 }

 static gboolean webkitTextCombinerPadEvent(GstPad* pad, GstObject* parent, GstEvent* event)
 {
     gboolean ret;
     UNUSED_PARAM(ret);
     WebKitTextCombiner* combiner = WEBKIT_TEXT_COMBINER(parent);
     WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(pad);
     ASSERT(combiner);

     switch (GST_EVENT_TYPE(event)) {
     case GST_EVENT_CAPS: {
         GstCaps* caps;
         gst_event_parse_caps(event, &caps);
         ASSERT(caps);

         GRefPtr<GstPad> target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)));
         GRefPtr<GstElement> targetParent = target ? adoptGRef(gst_pad_get_parent_element(target.get())) : nullptr;

         GRefPtr<GstCaps> textCaps = adoptGRef(gst_caps_new_empty_simple("text/x-raw"));
         if (gst_caps_can_intersect(textCaps.get(), caps)) {
             // Caps are plain text, we want a WebVTT encoder between the ghostpad and the funnel.
             if (!target || G_TYPE_FROM_INSTANCE(targetParent.get()) != webVTTEncType) {
                 // Setup a WebVTT encoder.
                 GstElement* encoder = gst_element_factory_make("webvttenc", nullptr);
                 ASSERT(encoder);

                 ret = gst_bin_add(GST_BIN(combiner), encoder);
                 ASSERT(ret);

                 ret = gst_element_sync_state_with_parent(encoder);
                 ASSERT(ret);

                 // Switch the ghostpad to target the WebVTT encoder.
                 GRefPtr<GstPad> sinkPad = adoptGRef(gst_element_get_static_pad(encoder, "sink"));
                 ASSERT(sinkPad);

                 ret = gst_ghost_pad_set_target(GST_GHOST_PAD(pad), sinkPad.get());
                 ASSERT(ret);

                 // Connect the WebVTT encoder to the funnel.
                 GRefPtr<GstPad> srcPad = adoptGRef(gst_element_get_static_pad(encoder, "src"));
                 ASSERT(srcPad);

                 ret = GST_PAD_LINK_SUCCESSFUL(gst_pad_link(srcPad.get(), combinerPad->funnelPad));
                 ASSERT(ret);
             } // Else: pipeline is already correct.
         } else {
             // Caps are not plain text, we assume it's WebVTT.

             // Remove the WebVTT encoder if present.
             if (target && G_TYPE_FROM_INSTANCE(targetParent.get()) == webVTTEncType) {
                 ret = gst_bin_remove(GST_BIN(combiner), targetParent.get());
                 ASSERT(ret);

                 target = nullptr;
                 targetParent = nullptr;
             }

             // Link the pad to the funnel.
             if (!target) {
                 ret = gst_ghost_pad_set_target(GST_GHOST_PAD(pad), combinerPad->funnelPad);
                 ASSERT(ret);
             } // Else: pipeline is already correct.
         }
         break;
     }
     case GST_EVENT_TAG: {
         GstTagList* tags;
         gst_event_parse_tag(event, &tags);
         ASSERT(tags);

         GST_OBJECT_LOCK(pad);
         if (!combinerPad->tags)
             combinerPad->tags = gst_tag_list_copy(tags);
         else
             gst_tag_list_insert(combinerPad->tags, tags, GST_TAG_MERGE_REPLACE);
         GST_OBJECT_UNLOCK(pad);

         g_object_notify(G_OBJECT(pad), "tags");
         break;
     }
     default:
         break;
     }
     return gst_pad_event_default(pad, parent, event);
 }

 static GstPad* webkitTextCombinerRequestNewPad(GstElement * element,
     GstPadTemplate * templ, const gchar * name, const GstCaps * caps)
 {
     gboolean ret;
     UNUSED_PARAM(ret);
     ASSERT(templ);

     WebKitTextCombiner* combiner = WEBKIT_TEXT_COMBINER(element);
     ASSERT(combiner);

     GstPad* ghostPad = GST_PAD(g_object_new(WEBKIT_TYPE_TEXT_COMBINER_PAD, "direction", GST_PAD_SINK, nullptr));
     ASSERT(ghostPad);

     ret = gst_ghost_pad_construct(GST_GHOST_PAD(ghostPad));
     ASSERT(ret);

     WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(ghostPad);
     combinerPad->funnelPad = gst_element_request_pad(combiner->funnel, templ, name, caps);
     ASSERT(combinerPad->funnelPad);

     ret = gst_pad_set_active(ghostPad, true);
     ASSERT(ret);

     ret = gst_element_add_pad(GST_ELEMENT(combiner), ghostPad);
     ASSERT(ret);
     return ghostPad;
 }

 static void webkitTextCombinerReleasePad(GstElement *element, GstPad *pad)
 {
     WebKitTextCombiner* combiner = WEBKIT_TEXT_COMBINER(element);
     WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(pad);

     if (GRefPtr<GstPad> target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)))) {
         GRefPtr<GstElement> parent = adoptGRef(gst_pad_get_parent_element(target.get()));
         ASSERT(parent);
         if (G_TYPE_FROM_INSTANCE(parent.get()) == webVTTEncType) {
             gst_element_set_state(parent.get(), GST_STATE_NULL);
             gst_bin_remove(GST_BIN(combiner), parent.get());
         }
     }

     gst_element_release_request_pad(combiner->funnel, combinerPad->funnelPad);
     gst_element_remove_pad(element, pad);
 }

 static void webkit_text_combiner_class_init(WebKitTextCombinerClass* klass)
 {
     GstElementClass* elementClass = GST_ELEMENT_CLASS(klass);

     gst_element_class_add_pad_template(elementClass, gst_static_pad_template_get(&sinkTemplate));
     gst_element_class_add_pad_template(elementClass, gst_static_pad_template_get(&srcTemplate));

     gst_element_class_set_metadata(elementClass, "WebKit text combiner", "Generic",
         "A funnel that accepts any caps, but converts plain text to WebVTT",
         "Brendan Long <b.long@cablelabs.com>");

     elementClass->request_new_pad =
         GST_DEBUG_FUNCPTR(webkitTextCombinerRequestNewPad);
     elementClass->release_pad =
         GST_DEBUG_FUNCPTR(webkitTextCombinerReleasePad);

     GRefPtr<GstElementFactory> webVTTEncFactory = adoptGRef(gst_element_factory_find("webvttenc"));
     ASSERT(webVTTEncFactory);
     gst_object_unref(gst_plugin_feature_load(GST_PLUGIN_FEATURE(webVTTEncFactory.get())));
     webVTTEncType = gst_element_factory_get_element_type(webVTTEncFactory.get());
     ASSERT(webVTTEncType);
 }

 static void webkit_text_combiner_pad_class_init(WebKitTextCombinerPadClass* klass)
 {
     GObjectClass* gobjectClass = G_OBJECT_CLASS(klass);

     gobjectClass->dispose = GST_DEBUG_FUNCPTR(webkitTextCombinerPadDispose);
     gobjectClass->get_property = GST_DEBUG_FUNCPTR(webkitTextCombinerPadGetProperty);

     g_object_class_install_property(gobjectClass, PROP_PAD_TAGS,
         g_param_spec_boxed("tags", "Tags", "The currently active tags on the pad", GST_TYPE_TAG_LIST,
             static_cast<GParamFlags>(G_PARAM_READABLE | G_PARAM_STATIC_STRINGS)));
 }

 GstElement* webkitTextCombinerNew()
 {
     // The combiner relies on webvttenc, fail early if it's not there.
     if (!WebCore::isGStreamerPluginAvailable("subenc")) {
         WTFLogAlways("WebKit wasn't able to find a WebVTT encoder. Not continuing without platform support for subtitles.");
         return nullptr;
     }

     return GST_ELEMENT(g_object_new(WEBKIT_TYPE_TEXT_COMBINER, nullptr));
 }

 #endif // ENABLE(VIDEO) && USE(GSTREAMER)
	/*
	* Copyright (C) 2013 Cable Television Laboratories, Inc.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
	* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	* DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
	* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
	* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
	* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
	* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "TextCombinerGStreamer.h"

	#if ENABLE(VIDEO) && USE(GSTREAMER)

	#include "GStreamerCommon.h"

	static GstStaticPadTemplate sinkTemplate =
	GST_STATIC_PAD_TEMPLATE("sink_%u", GST_PAD_SINK, GST_PAD_REQUEST,
	GST_STATIC_CAPS_ANY);

	static GstStaticPadTemplate srcTemplate =
	GST_STATIC_PAD_TEMPLATE("src", GST_PAD_SRC, GST_PAD_ALWAYS,
	GST_STATIC_CAPS_ANY);

	GST_DEBUG_CATEGORY_STATIC(webkitTextCombinerDebug);
	#define GST_CAT_DEFAULT webkitTextCombinerDebug

	#define webkit_text_combiner_parent_class parent_class
	G_DEFINE_TYPE_WITH_CODE(WebKitTextCombiner, webkit_text_combiner, GST_TYPE_BIN,
	GST_DEBUG_CATEGORY_INIT(webkitTextCombinerDebug, "webkittextcombiner", 0,
	"webkit text combiner"));

	enum {
	PROP_PAD_0,
	PROP_PAD_TAGS
	};

	#define WEBKIT_TYPE_TEXT_COMBINER_PAD webkit_text_combiner_pad_get_type()

	#define WEBKIT_TEXT_COMBINER_PAD(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj), WEBKIT_TYPE_TEXT_COMBINER_PAD, WebKitTextCombinerPad))
	#define WEBKIT_TEXT_COMBINER_PAD_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass), WEBKIT_TYPE_TEXT_COMBINER_PAD, WebKitTextCombinerPadClass))
	#define WEBKIT_IS_TEXT_COMBINER_PAD(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj), WEBKIT_TYPE_TEXT_COMBINER_PAD))
	#define WEBKIT_IS_TEXT_COMBINER_PAD_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass), WEBKIT_TYPE_TEXT_COMBINER_PAD))
	#define WEBKIT_TEXT_COMBINER_PAD_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS((obj), WEBKIT_TYPE_TEXT_COMBINER_PAD, WebKitTextCombinerPadClass))

	typedef struct _WebKitTextCombinerPad WebKitTextCombinerPad;
	typedef struct _WebKitTextCombinerPadClass WebKitTextCombinerPadClass;

	struct _WebKitTextCombinerPad {
	GstGhostPad parent;

	GstTagList* tags;
	GstPad* funnelPad;
	};

	struct _WebKitTextCombinerPadClass {
	GstGhostPadClass parent;
	};

	G_DEFINE_TYPE(WebKitTextCombinerPad, webkit_text_combiner_pad, GST_TYPE_GHOST_PAD);

	static GType webVTTEncType;

	static gboolean webkitTextCombinerPadEvent(GstPad, GstObject parent, GstEvent*);

	static void webkit_text_combiner_init(WebKitTextCombiner* combiner)
	{
	combiner->funnel = gst_element_factory_make("funnel", nullptr);
	ASSERT(combiner->funnel);

	gboolean ret = gst_bin_add(GST_BIN(combiner), combiner->funnel);
	UNUSED_PARAM(ret);
	ASSERT(ret);

	GRefPtr<GstPad> pad = adoptGRef(gst_element_get_static_pad(combiner->funnel, "src"));
	ASSERT(pad);

	ret = gst_element_add_pad(GST_ELEMENT(combiner), gst_ghost_pad_new("src", pad.get()));
	ASSERT(ret);
	}

	static void webkit_text_combiner_pad_init(WebKitTextCombinerPad* pad)
	{
	gst_pad_set_event_function(GST_PAD(pad), webkitTextCombinerPadEvent);
	}

	static void webkitTextCombinerPadDispose(GObject* object)
	{
	WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(object);
	g_clear_pointer(&combinerPad->tags, gst_tag_list_unref);
	g_clear_pointer(&combinerPad->funnelPad, gst_object_unref);
	G_OBJECT_CLASS(webkit_text_combiner_pad_parent_class)->dispose(object);
	}

	static void webkitTextCombinerPadGetProperty(GObject* object, guint propertyId, GValue* value, GParamSpec* pspec)
	{
	WebKitTextCombinerPad* pad = WEBKIT_TEXT_COMBINER_PAD(object);
	switch (propertyId) {
	case PROP_PAD_TAGS:
	GST_OBJECT_LOCK(object);
	if (pad->tags)
	g_value_take_boxed(value, gst_tag_list_copy(pad->tags));
	GST_OBJECT_UNLOCK(object);
	break;
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID(object, propertyId, pspec);
	break;
	}
	}

	static gboolean webkitTextCombinerPadEvent(GstPad* pad, GstObject* parent, GstEvent* event)
	{
	gboolean ret;
	UNUSED_PARAM(ret);
	WebKitTextCombiner* combiner = WEBKIT_TEXT_COMBINER(parent);
	WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(pad);
	ASSERT(combiner);

	switch (GST_EVENT_TYPE(event)) {
	case GST_EVENT_CAPS: {
	GstCaps* caps;
	gst_event_parse_caps(event, &caps);
	ASSERT(caps);

	GRefPtr<GstPad> target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)));
	GRefPtr<GstElement> targetParent = target ? adoptGRef(gst_pad_get_parent_element(target.get())) : nullptr;

	GRefPtr<GstCaps> textCaps = adoptGRef(gst_caps_new_empty_simple("text/x-raw"));
	if (gst_caps_can_intersect(textCaps.get(), caps)) {
	// Caps are plain text, we want a WebVTT encoder between the ghostpad and the funnel.
	if (!target \|\| G_TYPE_FROM_INSTANCE(targetParent.get()) != webVTTEncType) {
	// Setup a WebVTT encoder.
	GstElement* encoder = gst_element_factory_make("webvttenc", nullptr);
	ASSERT(encoder);

	ret = gst_bin_add(GST_BIN(combiner), encoder);
	ASSERT(ret);

	ret = gst_element_sync_state_with_parent(encoder);
	ASSERT(ret);

	// Switch the ghostpad to target the WebVTT encoder.
	GRefPtr<GstPad> sinkPad = adoptGRef(gst_element_get_static_pad(encoder, "sink"));
	ASSERT(sinkPad);

	ret = gst_ghost_pad_set_target(GST_GHOST_PAD(pad), sinkPad.get());
	ASSERT(ret);

	// Connect the WebVTT encoder to the funnel.
	GRefPtr<GstPad> srcPad = adoptGRef(gst_element_get_static_pad(encoder, "src"));
	ASSERT(srcPad);

	ret = GST_PAD_LINK_SUCCESSFUL(gst_pad_link(srcPad.get(), combinerPad->funnelPad));
	ASSERT(ret);
	} // Else: pipeline is already correct.
	} else {
	// Caps are not plain text, we assume it's WebVTT.

	// Remove the WebVTT encoder if present.
	if (target && G_TYPE_FROM_INSTANCE(targetParent.get()) == webVTTEncType) {
	ret = gst_bin_remove(GST_BIN(combiner), targetParent.get());
	ASSERT(ret);

	target = nullptr;
	targetParent = nullptr;
	}

	// Link the pad to the funnel.
	if (!target) {
	ret = gst_ghost_pad_set_target(GST_GHOST_PAD(pad), combinerPad->funnelPad);
	ASSERT(ret);
	} // Else: pipeline is already correct.
	}
	break;
	}
	case GST_EVENT_TAG: {
	GstTagList* tags;
	gst_event_parse_tag(event, &tags);
	ASSERT(tags);

	GST_OBJECT_LOCK(pad);
	if (!combinerPad->tags)
	combinerPad->tags = gst_tag_list_copy(tags);
	else
	gst_tag_list_insert(combinerPad->tags, tags, GST_TAG_MERGE_REPLACE);
	GST_OBJECT_UNLOCK(pad);

	g_object_notify(G_OBJECT(pad), "tags");
	break;
	}
	default:
	break;
	}
	return gst_pad_event_default(pad, parent, event);
	}

	static GstPad* webkitTextCombinerRequestNewPad(GstElement * element,
	GstPadTemplate * templ, const gchar * name, const GstCaps * caps)
	{
	gboolean ret;
	UNUSED_PARAM(ret);
	ASSERT(templ);

	WebKitTextCombiner* combiner = WEBKIT_TEXT_COMBINER(element);
	ASSERT(combiner);

	GstPad* ghostPad = GST_PAD(g_object_new(WEBKIT_TYPE_TEXT_COMBINER_PAD, "direction", GST_PAD_SINK, nullptr));
	ASSERT(ghostPad);

	ret = gst_ghost_pad_construct(GST_GHOST_PAD(ghostPad));
	ASSERT(ret);

	WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(ghostPad);
	combinerPad->funnelPad = gst_element_request_pad(combiner->funnel, templ, name, caps);
	ASSERT(combinerPad->funnelPad);

	ret = gst_pad_set_active(ghostPad, true);
	ASSERT(ret);

	ret = gst_element_add_pad(GST_ELEMENT(combiner), ghostPad);
	ASSERT(ret);
	return ghostPad;
	}

	static void webkitTextCombinerReleasePad(GstElement element, GstPad pad)
	{
	WebKitTextCombiner* combiner = WEBKIT_TEXT_COMBINER(element);
	WebKitTextCombinerPad* combinerPad = WEBKIT_TEXT_COMBINER_PAD(pad);

	if (GRefPtr<GstPad> target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)))) {
	GRefPtr<GstElement> parent = adoptGRef(gst_pad_get_parent_element(target.get()));
	ASSERT(parent);
	if (G_TYPE_FROM_INSTANCE(parent.get()) == webVTTEncType) {
	gst_element_set_state(parent.get(), GST_STATE_NULL);
	gst_bin_remove(GST_BIN(combiner), parent.get());
	}
	}

	gst_element_release_request_pad(combiner->funnel, combinerPad->funnelPad);
	gst_element_remove_pad(element, pad);
	}

	static void webkit_text_combiner_class_init(WebKitTextCombinerClass* klass)
	{
	GstElementClass* elementClass = GST_ELEMENT_CLASS(klass);

	gst_element_class_add_pad_template(elementClass, gst_static_pad_template_get(&sinkTemplate));
	gst_element_class_add_pad_template(elementClass, gst_static_pad_template_get(&srcTemplate));

	gst_element_class_set_metadata(elementClass, "WebKit text combiner", "Generic",
	"A funnel that accepts any caps, but converts plain text to WebVTT",
	"Brendan Long <b.long@cablelabs.com>");

	elementClass->request_new_pad =
	GST_DEBUG_FUNCPTR(webkitTextCombinerRequestNewPad);
	elementClass->release_pad =
	GST_DEBUG_FUNCPTR(webkitTextCombinerReleasePad);

	GRefPtr<GstElementFactory> webVTTEncFactory = adoptGRef(gst_element_factory_find("webvttenc"));
	ASSERT(webVTTEncFactory);
	gst_object_unref(gst_plugin_feature_load(GST_PLUGIN_FEATURE(webVTTEncFactory.get())));
	webVTTEncType = gst_element_factory_get_element_type(webVTTEncFactory.get());
	ASSERT(webVTTEncType);
	}

	static void webkit_text_combiner_pad_class_init(WebKitTextCombinerPadClass* klass)
	{
	GObjectClass* gobjectClass = G_OBJECT_CLASS(klass);

	gobjectClass->dispose = GST_DEBUG_FUNCPTR(webkitTextCombinerPadDispose);
	gobjectClass->get_property = GST_DEBUG_FUNCPTR(webkitTextCombinerPadGetProperty);

	g_object_class_install_property(gobjectClass, PROP_PAD_TAGS,
	g_param_spec_boxed("tags", "Tags", "The currently active tags on the pad", GST_TYPE_TAG_LIST,
	static_cast<GParamFlags>(G_PARAM_READABLE \| G_PARAM_STATIC_STRINGS)));
	}

	GstElement* webkitTextCombinerNew()
	{
	// The combiner relies on webvttenc, fail early if it's not there.
	if (!WebCore::isGStreamerPluginAvailable("subenc")) {
	WTFLogAlways("WebKit wasn't able to find a WebVTT encoder. Not continuing without platform support for subtitles.");
	return nullptr;
	}

	return GST_ELEMENT(g_object_new(WEBKIT_TYPE_TEXT_COMBINER, nullptr));
	}

	#endif // ENABLE(VIDEO) && USE(GSTREAMER)