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

 /*
  * Copyright (C) 2013 Cable Television Laboratories, Inc.
  * Copyright (C) 2021 Igalia S.L.
  *
  * 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"
 #include "TextCombinerPadGStreamer.h"
 #include <wtf/glib/WTFGType.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

 struct _WebKitTextCombinerPrivate {
     GRefPtr<GstElement> combinerElement;
 };

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

 using namespace WebCore;

 void webKitTextCombinerHandleCaps(WebKitTextCombiner* combiner, GstPad* pad, const GstCaps* caps)
 {
     ASSERT(caps);
     GST_DEBUG_OBJECT(combiner, "Handling caps %" GST_PTR_FORMAT, caps);

     auto target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)));
     auto targetParent = target ? adoptGRef(gst_pad_get_parent_element(target.get())) : nullptr;
     auto* combinerPad = WEBKIT_TEXT_COMBINER_PAD(pad);

     GRefPtr<GstPad> internalPad;
     g_object_get(combinerPad, "inner-combiner-pad", &internalPad.outPtr(), nullptr);

     auto cea608Caps = adoptGRef(gst_caps_new_empty_simple("closedcaption/x-cea-608"));
     auto 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 combinerElement.
         if (!target || gstElementFactoryEquals(targetParent.get(), "webvttenc"_s)) {
             GST_DEBUG_OBJECT(combiner, "Setting up a WebVTT encoder");
             auto* encoder = makeGStreamerElement("webvttenc", nullptr);
             ASSERT(encoder);

             gst_bin_add(GST_BIN_CAST(combiner), encoder);
             gst_element_sync_state_with_parent(encoder);

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

             gst_ghost_pad_set_target(GST_GHOST_PAD(pad), sinkPad.get());

             // Connect the WebVTT encoder to the combinerElement.
             auto srcPad = adoptGRef(gst_element_get_static_pad(encoder, "src"));
             ASSERT(srcPad);

             gst_pad_link(srcPad.get(), internalPad.get());
         } // Else: pipeline is already correct.
     } else if (gst_caps_can_intersect(cea608Caps.get(), caps)) {
         if (!isGStreamerPluginAvailable("rsclosedcaption") || !isGStreamerPluginAvailable("closedcaption")) {
             WTFLogAlways("GStreamer closedcaption plugins are missing. Please install gst-plugins-bad and gst-plugins-rs");
             return;
         }

         GST_DEBUG_OBJECT(combiner, "Converting CEA-608 closed captions to WebVTT.");
         auto* encoder = gst_bin_new(nullptr);
         auto* queue = gst_element_factory_make("queue", nullptr);
         auto* converter = makeGStreamerElement("ccconverter", nullptr);
         auto* rawCapsFilter = gst_element_factory_make("capsfilter", nullptr);
         auto* webvttEncoder = makeGStreamerElement("cea608tott", nullptr);
         auto* vttCapsFilter = gst_element_factory_make("capsfilter", nullptr);

         auto rawCaps = adoptGRef(gst_caps_new_simple("closedcaption/x-cea-608", "format", G_TYPE_STRING, "raw", nullptr));
         g_object_set(rawCapsFilter, "caps", rawCaps.get(), nullptr);
         auto vttCaps = adoptGRef(gst_caps_new_empty_simple("application/x-subtitle-vtt"));
         g_object_set(vttCapsFilter, "caps", vttCaps.get(), nullptr);

         gst_bin_add_many(GST_BIN_CAST(encoder), queue, converter, rawCapsFilter, webvttEncoder, vttCapsFilter, nullptr);
         gst_element_link_many(queue, converter, rawCapsFilter, webvttEncoder, vttCapsFilter, nullptr);

         auto encoderSinkPad = adoptGRef(gst_element_get_static_pad(queue, "sink"));
         auto* ghostSinkPad = gst_ghost_pad_new("sink", encoderSinkPad.get());
         gst_element_add_pad(encoder, ghostSinkPad);

         auto encoderSrcPad = adoptGRef(gst_element_get_static_pad(vttCapsFilter, "src"));
         auto* ghostSrcPad = gst_ghost_pad_new("src", encoderSrcPad.get());
         gst_element_add_pad(encoder, ghostSrcPad);

         gst_bin_add(GST_BIN_CAST(combiner), encoder);
         gst_element_sync_state_with_parent(encoder);

         gst_ghost_pad_set_target(GST_GHOST_PAD(pad), ghostSinkPad);
         gst_pad_link(ghostSrcPad, internalPad.get());
     } else {
         // Caps are not plain text or CEA-608, we assume it's WebVTT.

         // Remove the WebVTT encoder if present.
         if (target && targetParent) {
             GST_DEBUG_OBJECT(combiner, "Removing WebVTT encoder");
             gst_element_set_state(targetParent.get(), GST_STATE_NULL);
             gst_bin_remove(GST_BIN_CAST(combiner), targetParent.get());
             target = nullptr;
             targetParent = nullptr;
         }

         // Link the pad to the combinerElement.
         if (!target) {
             GST_DEBUG_OBJECT(combiner, "Associating %" GST_PTR_FORMAT " to %" GST_PTR_FORMAT, internalPad.get(), pad);
             gst_ghost_pad_set_target(GST_GHOST_PAD(pad), internalPad.get());
         } // Else: pipeline is already correct.
     }
 }

 static GstPad* webkitTextCombinerRequestNewPad(GstElement* element, GstPadTemplate* templ, const char* name, const GstCaps* caps)
 {
     auto* combiner = WEBKIT_TEXT_COMBINER(element);
     ASSERT(combiner);

     GST_DEBUG_OBJECT(element, "Requesting new sink pad");
     auto* ghostPad = GST_PAD_CAST(g_object_new(WEBKIT_TYPE_TEXT_COMBINER_PAD, "direction", GST_PAD_SINK, nullptr));
     ASSERT(ghostPad);

     auto* internalPad = gst_element_request_pad(combiner->priv->combinerElement.get(), templ, name, caps);
     g_object_set(WEBKIT_TEXT_COMBINER_PAD(ghostPad), "inner-combiner-pad", internalPad, nullptr);

     gst_pad_set_active(ghostPad, true);
     gst_element_add_pad(GST_ELEMENT_CAST(combiner), ghostPad);
     return ghostPad;
 }

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

     if (auto target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)))) {
         auto parent = adoptGRef(gst_pad_get_parent_element(target.get()));
         ASSERT(parent);
         if (parent) {
             gst_element_set_state(parent.get(), GST_STATE_NULL);
             gst_bin_remove(GST_BIN_CAST(combiner), parent.get());
         }
     }

     auto internalPad = adoptGRef(webKitTextCombinerPadLeakInternalPadRef(combinerPad));
     gst_element_release_request_pad(combiner->priv->combinerElement.get(), internalPad.get());

     gst_element_remove_pad(element, pad);
 }

 static void webKitTextCombinerConstructed(GObject* object)
 {
     GST_CALL_PARENT(G_OBJECT_CLASS, constructed, (object));

     auto* combiner = WEBKIT_TEXT_COMBINER(object);
     auto* priv = combiner->priv;

     priv->combinerElement = gst_element_factory_make("concat", nullptr);
     ASSERT(priv->combinerElement);
     g_object_set(priv->combinerElement.get(), "adjust-base", FALSE, nullptr);

     gst_bin_add(GST_BIN_CAST(combiner), priv->combinerElement.get());

     auto pad = adoptGRef(gst_element_get_static_pad(priv->combinerElement.get(), "src"));
     ASSERT(pad);

     gst_element_add_pad(GST_ELEMENT_CAST(combiner), gst_ghost_pad_new("src", pad.get()));
 }

 static void webkit_text_combiner_class_init(WebKitTextCombinerClass* klass)
 {
     auto* elementClass = GST_ELEMENT_CLASS(klass);
     auto* objectClass = G_OBJECT_CLASS(klass);

     objectClass->constructed = webKitTextCombinerConstructed;

     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 combiner 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);
 }

 GstElement* webkitTextCombinerNew()
 {
     // The combiner relies on webvttenc, fail early if it's not there.
     if (!isGStreamerPluginAvailable("subenc")) {
         WTFLogAlways("WebKit wasn't able to find a WebVTT encoder. Subtitles handling will be degraded unless gst-plugins-bad is installed.");
         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.
	* Copyright (C) 2021 Igalia S.L.
	*
	* 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"
	#include "TextCombinerPadGStreamer.h"
	#include <wtf/glib/WTFGType.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

	struct _WebKitTextCombinerPrivate {
	GRefPtr<GstElement> combinerElement;
	};

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

	using namespace WebCore;

	void webKitTextCombinerHandleCaps(WebKitTextCombiner* combiner, GstPad* pad, const GstCaps* caps)
	{
	ASSERT(caps);
	GST_DEBUG_OBJECT(combiner, "Handling caps %" GST_PTR_FORMAT, caps);

	auto target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)));
	auto targetParent = target ? adoptGRef(gst_pad_get_parent_element(target.get())) : nullptr;
	auto* combinerPad = WEBKIT_TEXT_COMBINER_PAD(pad);

	GRefPtr<GstPad> internalPad;
	g_object_get(combinerPad, "inner-combiner-pad", &internalPad.outPtr(), nullptr);

	auto cea608Caps = adoptGRef(gst_caps_new_empty_simple("closedcaption/x-cea-608"));
	auto 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 combinerElement.
	if (!target \|\| gstElementFactoryEquals(targetParent.get(), "webvttenc"_s)) {
	GST_DEBUG_OBJECT(combiner, "Setting up a WebVTT encoder");
	auto* encoder = makeGStreamerElement("webvttenc", nullptr);
	ASSERT(encoder);

	gst_bin_add(GST_BIN_CAST(combiner), encoder);
	gst_element_sync_state_with_parent(encoder);

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

	gst_ghost_pad_set_target(GST_GHOST_PAD(pad), sinkPad.get());

	// Connect the WebVTT encoder to the combinerElement.
	auto srcPad = adoptGRef(gst_element_get_static_pad(encoder, "src"));
	ASSERT(srcPad);

	gst_pad_link(srcPad.get(), internalPad.get());
	} // Else: pipeline is already correct.
	} else if (gst_caps_can_intersect(cea608Caps.get(), caps)) {
	if (!isGStreamerPluginAvailable("rsclosedcaption") \|\| !isGStreamerPluginAvailable("closedcaption")) {
	WTFLogAlways("GStreamer closedcaption plugins are missing. Please install gst-plugins-bad and gst-plugins-rs");
	return;
	}

	GST_DEBUG_OBJECT(combiner, "Converting CEA-608 closed captions to WebVTT.");
	auto* encoder = gst_bin_new(nullptr);
	auto* queue = gst_element_factory_make("queue", nullptr);
	auto* converter = makeGStreamerElement("ccconverter", nullptr);
	auto* rawCapsFilter = gst_element_factory_make("capsfilter", nullptr);
	auto* webvttEncoder = makeGStreamerElement("cea608tott", nullptr);
	auto* vttCapsFilter = gst_element_factory_make("capsfilter", nullptr);

	auto rawCaps = adoptGRef(gst_caps_new_simple("closedcaption/x-cea-608", "format", G_TYPE_STRING, "raw", nullptr));
	g_object_set(rawCapsFilter, "caps", rawCaps.get(), nullptr);
	auto vttCaps = adoptGRef(gst_caps_new_empty_simple("application/x-subtitle-vtt"));
	g_object_set(vttCapsFilter, "caps", vttCaps.get(), nullptr);

	gst_bin_add_many(GST_BIN_CAST(encoder), queue, converter, rawCapsFilter, webvttEncoder, vttCapsFilter, nullptr);
	gst_element_link_many(queue, converter, rawCapsFilter, webvttEncoder, vttCapsFilter, nullptr);

	auto encoderSinkPad = adoptGRef(gst_element_get_static_pad(queue, "sink"));
	auto* ghostSinkPad = gst_ghost_pad_new("sink", encoderSinkPad.get());
	gst_element_add_pad(encoder, ghostSinkPad);

	auto encoderSrcPad = adoptGRef(gst_element_get_static_pad(vttCapsFilter, "src"));
	auto* ghostSrcPad = gst_ghost_pad_new("src", encoderSrcPad.get());
	gst_element_add_pad(encoder, ghostSrcPad);

	gst_bin_add(GST_BIN_CAST(combiner), encoder);
	gst_element_sync_state_with_parent(encoder);

	gst_ghost_pad_set_target(GST_GHOST_PAD(pad), ghostSinkPad);
	gst_pad_link(ghostSrcPad, internalPad.get());
	} else {
	// Caps are not plain text or CEA-608, we assume it's WebVTT.

	// Remove the WebVTT encoder if present.
	if (target && targetParent) {
	GST_DEBUG_OBJECT(combiner, "Removing WebVTT encoder");
	gst_element_set_state(targetParent.get(), GST_STATE_NULL);
	gst_bin_remove(GST_BIN_CAST(combiner), targetParent.get());
	target = nullptr;
	targetParent = nullptr;
	}

	// Link the pad to the combinerElement.
	if (!target) {
	GST_DEBUG_OBJECT(combiner, "Associating %" GST_PTR_FORMAT " to %" GST_PTR_FORMAT, internalPad.get(), pad);
	gst_ghost_pad_set_target(GST_GHOST_PAD(pad), internalPad.get());
	} // Else: pipeline is already correct.
	}
	}

	static GstPad* webkitTextCombinerRequestNewPad(GstElement* element, GstPadTemplate* templ, const char* name, const GstCaps* caps)
	{
	auto* combiner = WEBKIT_TEXT_COMBINER(element);
	ASSERT(combiner);

	GST_DEBUG_OBJECT(element, "Requesting new sink pad");
	auto* ghostPad = GST_PAD_CAST(g_object_new(WEBKIT_TYPE_TEXT_COMBINER_PAD, "direction", GST_PAD_SINK, nullptr));
	ASSERT(ghostPad);

	auto* internalPad = gst_element_request_pad(combiner->priv->combinerElement.get(), templ, name, caps);
	g_object_set(WEBKIT_TEXT_COMBINER_PAD(ghostPad), "inner-combiner-pad", internalPad, nullptr);

	gst_pad_set_active(ghostPad, true);
	gst_element_add_pad(GST_ELEMENT_CAST(combiner), ghostPad);
	return ghostPad;
	}

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

	if (auto target = adoptGRef(gst_ghost_pad_get_target(GST_GHOST_PAD(pad)))) {
	auto parent = adoptGRef(gst_pad_get_parent_element(target.get()));
	ASSERT(parent);
	if (parent) {
	gst_element_set_state(parent.get(), GST_STATE_NULL);
	gst_bin_remove(GST_BIN_CAST(combiner), parent.get());
	}
	}

	auto internalPad = adoptGRef(webKitTextCombinerPadLeakInternalPadRef(combinerPad));
	gst_element_release_request_pad(combiner->priv->combinerElement.get(), internalPad.get());

	gst_element_remove_pad(element, pad);
	}

	static void webKitTextCombinerConstructed(GObject* object)
	{
	GST_CALL_PARENT(G_OBJECT_CLASS, constructed, (object));

	auto* combiner = WEBKIT_TEXT_COMBINER(object);
	auto* priv = combiner->priv;

	priv->combinerElement = gst_element_factory_make("concat", nullptr);
	ASSERT(priv->combinerElement);
	g_object_set(priv->combinerElement.get(), "adjust-base", FALSE, nullptr);

	gst_bin_add(GST_BIN_CAST(combiner), priv->combinerElement.get());

	auto pad = adoptGRef(gst_element_get_static_pad(priv->combinerElement.get(), "src"));
	ASSERT(pad);

	gst_element_add_pad(GST_ELEMENT_CAST(combiner), gst_ghost_pad_new("src", pad.get()));
	}

	static void webkit_text_combiner_class_init(WebKitTextCombinerClass* klass)
	{
	auto* elementClass = GST_ELEMENT_CLASS(klass);
	auto* objectClass = G_OBJECT_CLASS(klass);

	objectClass->constructed = webKitTextCombinerConstructed;

	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 combiner 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);
	}

	GstElement* webkitTextCombinerNew()
	{
	// The combiner relies on webvttenc, fail early if it's not there.
	if (!isGStreamerPluginAvailable("subenc")) {
	WTFLogAlways("WebKit wasn't able to find a WebVTT encoder. Subtitles handling will be degraded unless gst-plugins-bad is installed.");
	return nullptr;
	}

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

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