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

 /*
  * Copyright (C) 2020 Igalia S.L
  *
  * 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
  * aint with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */

 #include "config.h"
 #include "WebKitAudioSinkGStreamer.h"

 #if USE(GSTREAMER)

 #include "GStreamerAudioMixer.h"
 #include "GStreamerCommon.h"
 #include <gst/app/gstappsink.h>
 #include <gst/pbutils/missing-plugins.h>
 #include <sys/mman.h>
 #include <wtf/glib/WTFGType.h>

 #if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
 #include "PlatformDisplay.h"
 #include "PlatformDisplayLibWPE.h"
 #include <wpe/extensions/audio.h>
 #endif

 using namespace WebCore;

 struct _WebKitAudioSinkPrivate {
     GRefPtr<GstElement> interAudioSink;
     GRefPtr<GstPad> mixerPad;
     GRefPtr<GstElement> volumeElement;
     GRefPtr<GstElement> appsink;

 #if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
     GUniquePtr<struct wpe_audio_source> wpeAudioSource;
     int m_streamId;

     // wpe_audio_source state:
     // - GST_STATE_NULL: not started or EOS
     // - GST_STATE_PLAYING: at least one packet was emitted
     // - GST_STATE_PAUSED: pause notification was sent
     GstState sourceState;
 #endif
 };

 enum {
     PROP_0,
     PROP_VOLUME,
     PROP_MUTE,
 };

 static GstStaticPadTemplate sinkTemplate = GST_STATIC_PAD_TEMPLATE("sink", GST_PAD_SINK, GST_PAD_ALWAYS,
     GST_STATIC_CAPS("audio/x-raw"));

 GST_DEBUG_CATEGORY_STATIC(webkit_audio_sink_debug);
 #define GST_CAT_DEFAULT webkit_audio_sink_debug

 #define webkit_audio_sink_parent_class parent_class
 WEBKIT_DEFINE_TYPE_WITH_CODE(WebKitAudioSink, webkit_audio_sink, GST_TYPE_BIN,
     G_IMPLEMENT_INTERFACE(GST_TYPE_STREAM_VOLUME, nullptr);
     GST_DEBUG_CATEGORY_INIT(webkit_audio_sink_debug, "webkitaudiosink", 0, "webkit audio sink element")
 )

 #if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
 struct AudioPacketHolder {
     explicit AudioPacketHolder(GstBuffer* buffer)
     {
         this->buffer = GstMappedOwnedBuffer::create(buffer);
     }

     ~AudioPacketHolder()
     {
         if (fd)
             close(*fd);
     }

     std::optional<std::pair<uint32_t, size_t>> map()
     {
         fd = memfd_create("wpe-audio-buffer", MFD_CLOEXEC);
         if (*fd == -1)
             return std::nullopt;

         if (ftruncate(*fd, buffer->size()) == -1)
             return std::nullopt;

         ssize_t bytesWritten = write(*fd, buffer->data(), buffer->size());
         if (bytesWritten < 0)
             return std::nullopt;

         if (static_cast<size_t>(bytesWritten) != buffer->size())
             return std::nullopt;

         if (lseek(*fd, 0, SEEK_SET) == -1)
             return std::nullopt;

         return std::make_pair(static_cast<uint32_t>(*fd), buffer->size());
     }

     std::optional<int32_t> fd;
     RefPtr<GstMappedOwnedBuffer> buffer;
 };

 static void webKitAudioSinkHandleSample(WebKitAudioSink* sink, GRefPtr<GstSample>&& sample)
 {
     auto* wpeAudioSource = sink->priv->wpeAudioSource.get();
     static Atomic<int32_t> uniqueId;

     if (sink->priv->sourceState == GST_STATE_NULL) {
         sink->priv->m_streamId = uniqueId.exchangeAdd(1);
         GstCaps* caps = gst_sample_get_caps(sample.get());
         GstAudioInfo info;
         gst_audio_info_init(&info);
         gst_audio_info_from_caps(&info, caps);
         const char* format = gst_audio_format_to_string(GST_AUDIO_INFO_FORMAT(&info));
         wpe_audio_source_start(wpeAudioSource, sink->priv->m_streamId, GST_AUDIO_INFO_CHANNELS(&info), format, GST_AUDIO_INFO_RATE(&info));
         sink->priv->sourceState = GST_STATE_PLAYING;
     }

     auto* holder = new AudioPacketHolder(gst_sample_get_buffer(sample.get()));
     auto mapData = holder->map();
     if (!mapData) {
         GST_ERROR_OBJECT(sink, "Unable to prepare shared audio buffer");
         delete holder;
         return;
     }
     wpe_audio_source_packet(wpeAudioSource, sink->priv->m_streamId, mapData->first, mapData->second, [](void* data) {
         auto* holder = reinterpret_cast<AudioPacketHolder*>(data);
         delete holder;
     }, holder);
 }
 #endif

 static bool webKitAudioSinkConfigure(WebKitAudioSink* sink)
 {
 #if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
     sink->priv->sourceState = GST_STATE_NULL;
     auto& sharedDisplay = PlatformDisplay::sharedDisplay();
     if (is<PlatformDisplayLibWPE>(sharedDisplay)) {
         sink->priv->wpeAudioSource.reset(wpe_audio_source_create(downcast<PlatformDisplayLibWPE>(sharedDisplay).backend()));
         if (wpe_audio_source_has_receiver(sink->priv->wpeAudioSource.get())) {
             sink->priv->volumeElement = makeGStreamerElement("volume", nullptr);
             sink->priv->appsink = makeGStreamerElement("appsink", nullptr);
             gst_app_sink_set_emit_signals(GST_APP_SINK(sink->priv->appsink.get()), TRUE);

             g_signal_connect(sink->priv->appsink.get(), "new-sample", G_CALLBACK(+[](GstElement* appsink, WebKitAudioSink* sink) -> GstFlowReturn {
                 auto sample = adoptGRef(gst_app_sink_pull_sample(GST_APP_SINK(appsink)));
                 webKitAudioSinkHandleSample(sink, WTFMove(sample));
                 return GST_FLOW_OK;
             }), sink);
             g_signal_connect(sink->priv->appsink.get(), "new-preroll", G_CALLBACK(+[](GstElement* appsink, WebKitAudioSink* sink) -> GstFlowReturn {
                 auto sample = adoptGRef(gst_app_sink_pull_preroll(GST_APP_SINK(appsink)));
                 webKitAudioSinkHandleSample(sink, WTFMove(sample));
                 return GST_FLOW_OK;
             }), sink);

             g_signal_connect(sink->priv->appsink.get(), "eos", G_CALLBACK(+[](GstElement*, WebKitAudioSink* sink) {
                 wpe_audio_source_stop(sink->priv->wpeAudioSource.get(), sink->priv->m_streamId);
                 sink->priv->sourceState = GST_STATE_NULL;
             }), sink);

             gst_bin_add_many(GST_BIN_CAST(sink), sink->priv->volumeElement.get(), sink->priv->appsink.get(), nullptr);
             gst_element_link(sink->priv->volumeElement.get(), sink->priv->appsink.get());

             auto targetPad = adoptGRef(gst_element_get_static_pad(sink->priv->volumeElement.get(), "sink"));
             GstPad* sinkPad = webkitGstGhostPadFromStaticTemplate(&sinkTemplate, "sink", targetPad.get());
             gst_element_add_pad(GST_ELEMENT_CAST(sink), sinkPad);
             GST_OBJECT_FLAG_SET(sinkPad, GST_PAD_FLAG_NEED_PARENT);
             return true;
         }
     }
 #endif

     const char* value = g_getenv("WEBKIT_GST_ENABLE_AUDIO_MIXER");
     if (value && !strcmp(value, "1")) {
         if (!GStreamerAudioMixer::isAvailable()) {
             GST_WARNING("Internal audio mixing request cannot be fulfilled.");
             return false;
         }

         sink->priv->interAudioSink = makeGStreamerElement("interaudiosink", nullptr);
         RELEASE_ASSERT(sink->priv->interAudioSink);

         gst_bin_add(GST_BIN_CAST(sink), sink->priv->interAudioSink.get());
         auto targetPad = adoptGRef(gst_element_get_static_pad(sink->priv->interAudioSink.get(), "sink"));
         gst_element_add_pad(GST_ELEMENT_CAST(sink), webkitGstGhostPadFromStaticTemplate(&sinkTemplate, "sink", targetPad.get()));
         return true;
     }
     return false;
 }

 static GstObject* getInternalVolumeObject(WebKitAudioSink* sink)
 {
     if (sink->priv->volumeElement)
         return GST_OBJECT_CAST(sink->priv->volumeElement.get());

     RELEASE_ASSERT(sink->priv->mixerPad);
     return GST_OBJECT_CAST(sink->priv->mixerPad.get());
 }

 static void webKitAudioSinkSetProperty(GObject* object, guint propID, const GValue* value, GParamSpec* pspec)
 {
     WebKitAudioSink* sink = WEBKIT_AUDIO_SINK(object);

     switch (propID) {
     case PROP_VOLUME: {
         GstObject* internalObject = getInternalVolumeObject(sink);
         g_object_set_property(G_OBJECT(internalObject), "volume", value);
         break;
     }
     case PROP_MUTE: {
         GstObject* internalObject = getInternalVolumeObject(sink);
         g_object_set_property(G_OBJECT(internalObject), "mute", value);
         break;
     }
     default:
         G_OBJECT_WARN_INVALID_PROPERTY_ID(object, propID, pspec);
         break;
     }
 }

 static void webKitAudioSinkGetProperty(GObject* object, guint propID, GValue* value, GParamSpec* pspec)
 {
     WebKitAudioSink* sink = WEBKIT_AUDIO_SINK(object);

     switch (propID) {
     case PROP_VOLUME: {
         GstObject* internalObject = getInternalVolumeObject(sink);
         g_object_get_property(G_OBJECT(internalObject), "volume", value);
         break;
     }
     case PROP_MUTE: {
         GstObject* internalObject = getInternalVolumeObject(sink);
         g_object_get_property(G_OBJECT(internalObject), "mute", value);
         break;
     }
     default:
         G_OBJECT_WARN_INVALID_PROPERTY_ID(object, propID, pspec);
         break;
     }
 }

 static GstStateChangeReturn webKitAudioSinkChangeState(GstElement* element, GstStateChange stateChange)
 {
     auto* sink = WEBKIT_AUDIO_SINK(element);
     auto* priv = sink->priv;

     GST_DEBUG_OBJECT(sink, "Handling %s transition", gst_state_change_get_name(stateChange));

     auto& mixer = GStreamerAudioMixer::singleton();
     if (priv->interAudioSink && stateChange == GST_STATE_CHANGE_NULL_TO_READY)
         priv->mixerPad = mixer.registerProducer(priv->interAudioSink.get());

     if (priv->mixerPad)
         mixer.ensureState(stateChange);

     GstStateChangeReturn result = GST_CALL_PARENT_WITH_DEFAULT(GST_ELEMENT_CLASS, change_state, (element, stateChange), GST_STATE_CHANGE_FAILURE);

 #if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
     if (priv->appsink) {
         bool isEOS = gst_app_sink_is_eos(GST_APP_SINK(priv->appsink.get()));
         if ((stateChange == GST_STATE_CHANGE_PLAYING_TO_PAUSED) && !isEOS) {
             wpe_audio_source_pause(priv->wpeAudioSource.get(), priv->m_streamId);
             priv->sourceState = GST_STATE_PAUSED;
         }
         if (stateChange == GST_STATE_CHANGE_PAUSED_TO_READY && isEOS)
             priv->sourceState = GST_STATE_NULL;
     }
 #endif

     if (priv->mixerPad && stateChange == GST_STATE_CHANGE_READY_TO_NULL && result > GST_STATE_CHANGE_FAILURE) {
         mixer.unregisterProducer(priv->mixerPad);
         priv->mixerPad = nullptr;
     }
 #if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
     if (priv->appsink && priv->sourceState == GST_STATE_PAUSED && stateChange == GST_STATE_CHANGE_PAUSED_TO_PLAYING && result > GST_STATE_CHANGE_FAILURE) {
         wpe_audio_source_resume(priv->wpeAudioSource.get(), priv->m_streamId);
         priv->sourceState = GST_STATE_PLAYING;
     }
 #endif

     return result;
 }

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

     GST_OBJECT_FLAG_SET(GST_OBJECT_CAST(object), GST_ELEMENT_FLAG_SINK);
     gst_bin_set_suppressed_flags(GST_BIN_CAST(object), static_cast<GstElementFlags>(GST_ELEMENT_FLAG_SOURCE | GST_ELEMENT_FLAG_SINK));
 }

 static void webkit_audio_sink_class_init(WebKitAudioSinkClass* klass)
 {
     GObjectClass* oklass = G_OBJECT_CLASS(klass);
     oklass->set_property = webKitAudioSinkSetProperty;
     oklass->get_property = webKitAudioSinkGetProperty;
     oklass->constructed = webKitAudioSinkConstructed;

     g_object_class_install_property(oklass, PROP_VOLUME,
         g_param_spec_double("volume", "Volume", "The audio volume, 1.0=100%", 0, 10, 1,
             static_cast<GParamFlags>(G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
     g_object_class_install_property(oklass, PROP_MUTE,
         g_param_spec_boolean("mute", "Mute", "Mute the audio channel without changing the volume", FALSE,
             static_cast<GParamFlags>(G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));

     GstElementClass* eklass = GST_ELEMENT_CLASS(klass);
     gst_element_class_add_static_pad_template(eklass, &sinkTemplate);
     gst_element_class_set_metadata(eklass, "WebKit Audio sink element", "Sink/Audio",
         "Proxies audio data to WebKit's audio mixer or to a WPE external audio handler",
         "Philippe Normand <philn@igalia.com>");

     eklass->change_state = GST_DEBUG_FUNCPTR(webKitAudioSinkChangeState);
 }

 GstElement* webkitAudioSinkNew()
 {
     auto* sink = GST_ELEMENT_CAST(g_object_new(WEBKIT_TYPE_AUDIO_SINK, nullptr));
     if (!webKitAudioSinkConfigure(WEBKIT_AUDIO_SINK(sink))) {
         gst_object_unref(sink);
         return nullptr;
     }
     return sink;
 }

 #endif // USE(GSTREAMER)
	/*
	* Copyright (C) 2020 Igalia S.L
	*
	* 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
	* aint with this library; see the file COPYING.LIB. If not, write to
	* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
	* Boston, MA 02110-1301, USA.
	*/

	#include "config.h"
	#include "WebKitAudioSinkGStreamer.h"

	#if USE(GSTREAMER)

	#include "GStreamerAudioMixer.h"
	#include "GStreamerCommon.h"
	#include <gst/app/gstappsink.h>
	#include <gst/pbutils/missing-plugins.h>
	#include <sys/mman.h>
	#include <wtf/glib/WTFGType.h>

	#if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
	#include "PlatformDisplay.h"
	#include "PlatformDisplayLibWPE.h"
	#include <wpe/extensions/audio.h>
	#endif

	using namespace WebCore;

	struct _WebKitAudioSinkPrivate {
	GRefPtr<GstElement> interAudioSink;
	GRefPtr<GstPad> mixerPad;
	GRefPtr<GstElement> volumeElement;
	GRefPtr<GstElement> appsink;

	#if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
	GUniquePtr<struct wpe_audio_source> wpeAudioSource;
	int m_streamId;

	// wpe_audio_source state:
	// - GST_STATE_NULL: not started or EOS
	// - GST_STATE_PLAYING: at least one packet was emitted
	// - GST_STATE_PAUSED: pause notification was sent
	GstState sourceState;
	#endif
	};

	enum {
	PROP_0,
	PROP_VOLUME,
	PROP_MUTE,
	};

	static GstStaticPadTemplate sinkTemplate = GST_STATIC_PAD_TEMPLATE("sink", GST_PAD_SINK, GST_PAD_ALWAYS,
	GST_STATIC_CAPS("audio/x-raw"));

	GST_DEBUG_CATEGORY_STATIC(webkit_audio_sink_debug);
	#define GST_CAT_DEFAULT webkit_audio_sink_debug

	#define webkit_audio_sink_parent_class parent_class
	WEBKIT_DEFINE_TYPE_WITH_CODE(WebKitAudioSink, webkit_audio_sink, GST_TYPE_BIN,
	G_IMPLEMENT_INTERFACE(GST_TYPE_STREAM_VOLUME, nullptr);
	GST_DEBUG_CATEGORY_INIT(webkit_audio_sink_debug, "webkitaudiosink", 0, "webkit audio sink element")
	)

	#if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
	struct AudioPacketHolder {
	explicit AudioPacketHolder(GstBuffer* buffer)
	{
	this->buffer = GstMappedOwnedBuffer::create(buffer);
	}

	~AudioPacketHolder()
	{
	if (fd)
	close(*fd);
	}

	std::optional<std::pair<uint32_t, size_t>> map()
	{
	fd = memfd_create("wpe-audio-buffer", MFD_CLOEXEC);
	if (*fd == -1)
	return std::nullopt;

	if (ftruncate(*fd, buffer->size()) == -1)
	return std::nullopt;

	ssize_t bytesWritten = write(*fd, buffer->data(), buffer->size());
	if (bytesWritten < 0)
	return std::nullopt;

	if (static_cast<size_t>(bytesWritten) != buffer->size())
	return std::nullopt;

	if (lseek(*fd, 0, SEEK_SET) == -1)
	return std::nullopt;

	return std::make_pair(static_cast<uint32_t>(*fd), buffer->size());
	}

	std::optional<int32_t> fd;
	RefPtr<GstMappedOwnedBuffer> buffer;
	};

	static void webKitAudioSinkHandleSample(WebKitAudioSink* sink, GRefPtr<GstSample>&& sample)
	{
	auto* wpeAudioSource = sink->priv->wpeAudioSource.get();
	static Atomic<int32_t> uniqueId;

	if (sink->priv->sourceState == GST_STATE_NULL) {
	sink->priv->m_streamId = uniqueId.exchangeAdd(1);
	GstCaps* caps = gst_sample_get_caps(sample.get());
	GstAudioInfo info;
	gst_audio_info_init(&info);
	gst_audio_info_from_caps(&info, caps);
	const char* format = gst_audio_format_to_string(GST_AUDIO_INFO_FORMAT(&info));
	wpe_audio_source_start(wpeAudioSource, sink->priv->m_streamId, GST_AUDIO_INFO_CHANNELS(&info), format, GST_AUDIO_INFO_RATE(&info));
	sink->priv->sourceState = GST_STATE_PLAYING;
	}

	auto* holder = new AudioPacketHolder(gst_sample_get_buffer(sample.get()));
	auto mapData = holder->map();
	if (!mapData) {
	GST_ERROR_OBJECT(sink, "Unable to prepare shared audio buffer");
	delete holder;
	return;
	}
	wpe_audio_source_packet(wpeAudioSource, sink->priv->m_streamId, mapData->first, mapData->second, [](void* data) {
	auto* holder = reinterpret_cast<AudioPacketHolder*>(data);
	delete holder;
	}, holder);
	}
	#endif

	static bool webKitAudioSinkConfigure(WebKitAudioSink* sink)
	{
	#if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
	sink->priv->sourceState = GST_STATE_NULL;
	auto& sharedDisplay = PlatformDisplay::sharedDisplay();
	if (is<PlatformDisplayLibWPE>(sharedDisplay)) {
	sink->priv->wpeAudioSource.reset(wpe_audio_source_create(downcast<PlatformDisplayLibWPE>(sharedDisplay).backend()));
	if (wpe_audio_source_has_receiver(sink->priv->wpeAudioSource.get())) {
	sink->priv->volumeElement = makeGStreamerElement("volume", nullptr);
	sink->priv->appsink = makeGStreamerElement("appsink", nullptr);
	gst_app_sink_set_emit_signals(GST_APP_SINK(sink->priv->appsink.get()), TRUE);

	g_signal_connect(sink->priv->appsink.get(), "new-sample", G_CALLBACK(+[](GstElement* appsink, WebKitAudioSink* sink) -> GstFlowReturn {
	auto sample = adoptGRef(gst_app_sink_pull_sample(GST_APP_SINK(appsink)));
	webKitAudioSinkHandleSample(sink, WTFMove(sample));
	return GST_FLOW_OK;
	}), sink);
	g_signal_connect(sink->priv->appsink.get(), "new-preroll", G_CALLBACK(+[](GstElement* appsink, WebKitAudioSink* sink) -> GstFlowReturn {
	auto sample = adoptGRef(gst_app_sink_pull_preroll(GST_APP_SINK(appsink)));
	webKitAudioSinkHandleSample(sink, WTFMove(sample));
	return GST_FLOW_OK;
	}), sink);

	g_signal_connect(sink->priv->appsink.get(), "eos", G_CALLBACK(+[](GstElement, WebKitAudioSink sink) {
	wpe_audio_source_stop(sink->priv->wpeAudioSource.get(), sink->priv->m_streamId);
	sink->priv->sourceState = GST_STATE_NULL;
	}), sink);

	gst_bin_add_many(GST_BIN_CAST(sink), sink->priv->volumeElement.get(), sink->priv->appsink.get(), nullptr);
	gst_element_link(sink->priv->volumeElement.get(), sink->priv->appsink.get());

	auto targetPad = adoptGRef(gst_element_get_static_pad(sink->priv->volumeElement.get(), "sink"));
	GstPad* sinkPad = webkitGstGhostPadFromStaticTemplate(&sinkTemplate, "sink", targetPad.get());
	gst_element_add_pad(GST_ELEMENT_CAST(sink), sinkPad);
	GST_OBJECT_FLAG_SET(sinkPad, GST_PAD_FLAG_NEED_PARENT);
	return true;
	}
	}
	#endif

	const char* value = g_getenv("WEBKIT_GST_ENABLE_AUDIO_MIXER");
	if (value && !strcmp(value, "1")) {
	if (!GStreamerAudioMixer::isAvailable()) {
	GST_WARNING("Internal audio mixing request cannot be fulfilled.");
	return false;
	}

	sink->priv->interAudioSink = makeGStreamerElement("interaudiosink", nullptr);
	RELEASE_ASSERT(sink->priv->interAudioSink);

	gst_bin_add(GST_BIN_CAST(sink), sink->priv->interAudioSink.get());
	auto targetPad = adoptGRef(gst_element_get_static_pad(sink->priv->interAudioSink.get(), "sink"));
	gst_element_add_pad(GST_ELEMENT_CAST(sink), webkitGstGhostPadFromStaticTemplate(&sinkTemplate, "sink", targetPad.get()));
	return true;
	}
	return false;
	}

	static GstObject* getInternalVolumeObject(WebKitAudioSink* sink)
	{
	if (sink->priv->volumeElement)
	return GST_OBJECT_CAST(sink->priv->volumeElement.get());

	RELEASE_ASSERT(sink->priv->mixerPad);
	return GST_OBJECT_CAST(sink->priv->mixerPad.get());
	}

	static void webKitAudioSinkSetProperty(GObject* object, guint propID, const GValue* value, GParamSpec* pspec)
	{
	WebKitAudioSink* sink = WEBKIT_AUDIO_SINK(object);

	switch (propID) {
	case PROP_VOLUME: {
	GstObject* internalObject = getInternalVolumeObject(sink);
	g_object_set_property(G_OBJECT(internalObject), "volume", value);
	break;
	}
	case PROP_MUTE: {
	GstObject* internalObject = getInternalVolumeObject(sink);
	g_object_set_property(G_OBJECT(internalObject), "mute", value);
	break;
	}
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID(object, propID, pspec);
	break;
	}
	}

	static void webKitAudioSinkGetProperty(GObject* object, guint propID, GValue* value, GParamSpec* pspec)
	{
	WebKitAudioSink* sink = WEBKIT_AUDIO_SINK(object);

	switch (propID) {
	case PROP_VOLUME: {
	GstObject* internalObject = getInternalVolumeObject(sink);
	g_object_get_property(G_OBJECT(internalObject), "volume", value);
	break;
	}
	case PROP_MUTE: {
	GstObject* internalObject = getInternalVolumeObject(sink);
	g_object_get_property(G_OBJECT(internalObject), "mute", value);
	break;
	}
	default:
	G_OBJECT_WARN_INVALID_PROPERTY_ID(object, propID, pspec);
	break;
	}
	}

	static GstStateChangeReturn webKitAudioSinkChangeState(GstElement* element, GstStateChange stateChange)
	{
	auto* sink = WEBKIT_AUDIO_SINK(element);
	auto* priv = sink->priv;

	GST_DEBUG_OBJECT(sink, "Handling %s transition", gst_state_change_get_name(stateChange));

	auto& mixer = GStreamerAudioMixer::singleton();
	if (priv->interAudioSink && stateChange == GST_STATE_CHANGE_NULL_TO_READY)
	priv->mixerPad = mixer.registerProducer(priv->interAudioSink.get());

	if (priv->mixerPad)
	mixer.ensureState(stateChange);

	GstStateChangeReturn result = GST_CALL_PARENT_WITH_DEFAULT(GST_ELEMENT_CLASS, change_state, (element, stateChange), GST_STATE_CHANGE_FAILURE);

	#if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
	if (priv->appsink) {
	bool isEOS = gst_app_sink_is_eos(GST_APP_SINK(priv->appsink.get()));
	if ((stateChange == GST_STATE_CHANGE_PLAYING_TO_PAUSED) && !isEOS) {
	wpe_audio_source_pause(priv->wpeAudioSource.get(), priv->m_streamId);
	priv->sourceState = GST_STATE_PAUSED;
	}
	if (stateChange == GST_STATE_CHANGE_PAUSED_TO_READY && isEOS)
	priv->sourceState = GST_STATE_NULL;
	}
	#endif

	if (priv->mixerPad && stateChange == GST_STATE_CHANGE_READY_TO_NULL && result > GST_STATE_CHANGE_FAILURE) {
	mixer.unregisterProducer(priv->mixerPad);
	priv->mixerPad = nullptr;
	}
	#if PLATFORM(WPE) && USE(WPEBACKEND_FDO_AUDIO_EXTENSION)
	if (priv->appsink && priv->sourceState == GST_STATE_PAUSED && stateChange == GST_STATE_CHANGE_PAUSED_TO_PLAYING && result > GST_STATE_CHANGE_FAILURE) {
	wpe_audio_source_resume(priv->wpeAudioSource.get(), priv->m_streamId);
	priv->sourceState = GST_STATE_PLAYING;
	}
	#endif

	return result;
	}

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

	GST_OBJECT_FLAG_SET(GST_OBJECT_CAST(object), GST_ELEMENT_FLAG_SINK);
	gst_bin_set_suppressed_flags(GST_BIN_CAST(object), static_cast<GstElementFlags>(GST_ELEMENT_FLAG_SOURCE \| GST_ELEMENT_FLAG_SINK));
	}

	static void webkit_audio_sink_class_init(WebKitAudioSinkClass* klass)
	{
	GObjectClass* oklass = G_OBJECT_CLASS(klass);
	oklass->set_property = webKitAudioSinkSetProperty;
	oklass->get_property = webKitAudioSinkGetProperty;
	oklass->constructed = webKitAudioSinkConstructed;

	g_object_class_install_property(oklass, PROP_VOLUME,
	g_param_spec_double("volume", "Volume", "The audio volume, 1.0=100%", 0, 10, 1,
	static_cast<GParamFlags>(G_PARAM_READWRITE \| G_PARAM_STATIC_STRINGS)));
	g_object_class_install_property(oklass, PROP_MUTE,
	g_param_spec_boolean("mute", "Mute", "Mute the audio channel without changing the volume", FALSE,
	static_cast<GParamFlags>(G_PARAM_READWRITE \| G_PARAM_STATIC_STRINGS)));

	GstElementClass* eklass = GST_ELEMENT_CLASS(klass);
	gst_element_class_add_static_pad_template(eklass, &sinkTemplate);
	gst_element_class_set_metadata(eklass, "WebKit Audio sink element", "Sink/Audio",
	"Proxies audio data to WebKit's audio mixer or to a WPE external audio handler",
	"Philippe Normand <philn@igalia.com>");

	eklass->change_state = GST_DEBUG_FUNCPTR(webKitAudioSinkChangeState);
	}

	GstElement* webkitAudioSinkNew()
	{
	auto* sink = GST_ELEMENT_CAST(g_object_new(WEBKIT_TYPE_AUDIO_SINK, nullptr));
	if (!webKitAudioSinkConfigure(WEBKIT_AUDIO_SINK(sink))) {
	gst_object_unref(sink);
	return nullptr;
	}
	return sink;
	}

	#endif // USE(GSTREAMER)