wpe: Implement audio support

The wpesrc bin now exposes "sometimes" audio src pads, one for every PCM audio
stream created by WPEWebKit.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2252>

8 files changed, 384 insertions, 30 deletions

diff --git a/ext/wpe/WPEThreadedView.cpp b/ext/wpe/WPEThreadedView.cpp
index e95b2bb5d..c075e9ae1 100644
--- a/ext/wpe/WPEThreadedView.cpp
+++ b/ext/wpe/WPEThreadedView.cpp
@@ -286,7 +286,10 @@ WPEView::WPEView(WebKitWebContext* web_context, GstWpeVideoSrc* src, GstGLContex
     wpe_view_backend_add_activity_state(wpeViewBackend, wpe_view_activity_state_visible | wpe_view_activity_state_focused | wpe_view_activity_state_in_window);
 #endif
 
-    webkit.view = WEBKIT_WEB_VIEW(g_object_new(WEBKIT_TYPE_WEB_VIEW, "web-context", web_context, "backend", viewBackend, nullptr));
+    webkit.view = WEBKIT_WEB_VIEW(g_object_new(WEBKIT_TYPE_WEB_VIEW,
+        "web-context", web_context,
+        "backend", viewBackend,
+        nullptr));
 
     g_signal_connect(webkit.view, "load-failed", G_CALLBACK(s_loadFailed), src);
     g_signal_connect(webkit.view, "load-failed-with-tls-errors", G_CALLBACK(s_loadFailedWithTLSErrors), src);
@@ -517,6 +520,11 @@ void WPEView::setDrawBackground(gboolean drawsBackground)
     webkit_web_view_set_background_color(webkit.view, &color);
 }
 
+void WPEView::registerAudioReceiver(const struct wpe_audio_receiver* audioReceiver, gpointer userData)
+{
+    wpe_audio_register_receiver(audioReceiver, userData);
+}
+
 void WPEView::releaseImage(gpointer imagePointer)
 {
     s_view->dispatch([&]() {
diff --git a/ext/wpe/WPEThreadedView.h b/ext/wpe/WPEThreadedView.h
index 414d9b209..31d564295 100644
--- a/ext/wpe/WPEThreadedView.h
+++ b/ext/wpe/WPEThreadedView.h
@@ -23,6 +23,7 @@
 #include <glib.h>
 #include <gst/gl/gstglfuncs.h>
 #include <gst/gl/egl/gstgldisplay_egl.h>
+#include <wpe/extensions/audio.h>
 #include <wpe/fdo.h>
 #include <wpe/fdo-egl.h>
 #include <wpe/webkit.h>
@@ -50,6 +51,9 @@ public:
     void loadUri(const gchar*);
     void loadData(GBytes*);
     void setDrawBackground(gboolean);
+
+    void registerAudioReceiver(const struct wpe_audio_receiver*, gpointer);
+
     GstEGLImage* image();
     GstBuffer* buffer();
 
@@ -96,7 +100,7 @@ private:
         struct wpe_view_backend_exportable_fdo* exportable;
         int width;
         int height;
-    } wpe { nullptr, 0, 0 };
+    } wpe { nullptr, 0, 0, };
 
     struct {
         gchar* uri;
diff --git a/ext/wpe/gstwpe-private.h b/ext/wpe/gstwpe-private.h
new file mode 100644
index 000000000..8eed9914d
--- /dev/null
+++ b/ext/wpe/gstwpe-private.h
@@ -0,0 +1,24 @@
+/* Copyright (C) <2018, 2019> Philippe Normand <philn@igalia.com>
+ * Copyright (C) <2018, 2019> Žan Doberšek <zdobersek@igalia.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.
+ */
+
+#pragma once
+
+#include <gst/gst.h>
+
+void gst_wpe_video_src_register_audio_receiver(GstElement*, const struct wpe_audio_receiver*, gpointer);
diff --git a/ext/wpe/gstwpe.cpp b/ext/wpe/gstwpe.cpp
index 51dba610d..30f90f3d9 100644
--- a/ext/wpe/gstwpe.cpp
+++ b/ext/wpe/gstwpe.cpp
@@ -68,12 +68,14 @@
 
 GST_DEBUG_CATEGORY (wpe_video_src_debug);
 GST_DEBUG_CATEGORY (wpe_view_debug);
+GST_DEBUG_CATEGORY (wpe_src_debug);
 
 static gboolean
 plugin_init (GstPlugin * plugin)
 {
-  GST_DEBUG_CATEGORY_INIT (wpe_video_src_debug, "wpesrc", 0, "WPE Source");
+  GST_DEBUG_CATEGORY_INIT (wpe_video_src_debug, "wpevideosrc", 0, "WPE Video Source");
   GST_DEBUG_CATEGORY_INIT (wpe_view_debug, "wpeview", 0, "WPE Threaded View");
+  GST_DEBUG_CATEGORY_INIT (wpe_src_debug, "wpesrc", 0, "WPE Source");
 
   gboolean result = gst_element_register (plugin, "wpevideosrc", GST_RANK_NONE,
       GST_TYPE_WPE_VIDEO_SRC);
diff --git a/ext/wpe/gstwpesrcbin.cpp b/ext/wpe/gstwpesrcbin.cpp
index 58349eeef..2a39a8112 100644
--- a/ext/wpe/gstwpesrcbin.cpp
+++ b/ext/wpe/gstwpesrcbin.cpp
@@ -1,5 +1,5 @@
-/* Copyright (C) <2018> Philippe Normand <philn@igalia.com>
- * Copyright (C) <2018> Žan Doberšek <zdobersek@igalia.com>
+/* Copyright (C) <2018, 2019> Philippe Normand <philn@igalia.com>
+ * Copyright (C) <2018, 2019> Žan Doberšek <zdobersek@igalia.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -21,20 +21,65 @@
  * SECTION:element-wpesrc
  * @title: wpesrc
  *
- * FIXME The wpesrc element is used to produce a video texture representing a
- * web page rendered off-screen by WPE.
+ * The wpesrc element is used to produce a video texture representing a web page
+ * rendered off-screen by WPE.
  *
+ * Starting from WPEBackend-FDO 1.6.x, software rendering support is available.
+ * This features allows wpesrc to be used on machines without GPU, and/or for
+ * testing purpose. To enable it, set the `LIBGL_ALWAYS_SOFTWARE=true`
+ * environment variable and make sure `video/x-raw, format=BGRA` caps are
+ * negotiated by the wpesrc element.
+ *
+ * Additionally, any audio stream created by WPE is exposed as "sometimes" audio
+ * source pads.
  */
 
 #include "gstwpesrcbin.h"
 #include "gstwpevideosrc.h"
+#include "gstwpe-private.h"
 #include "WPEThreadedView.h"
 
+#include <gst/allocators/allocators.h>
+#include <gst/base/gstflowcombiner.h>
+#include <wpe/extensions/audio.h>
+
+G_DEFINE_TYPE (GstWpeAudioPad, gst_wpe_audio_pad, GST_TYPE_GHOST_PAD);
+
+static void
+gst_wpe_audio_pad_class_init (GstWpeAudioPadClass * klass)
+{
+}
+
+static void
+gst_wpe_audio_pad_init (GstWpeAudioPad * pad)
+{
+  gst_audio_info_init (&pad->info);
+  pad->discont_pending = FALSE;
+  pad->buffer_time = GST_CLOCK_TIME_NONE;
+}
+
+static GstWpeAudioPad *
+gst_wpe_audio_pad_new (const gchar * name)
+{
+  GstWpeAudioPad *pad = GST_WPE_AUDIO_PAD (g_object_new (gst_wpe_audio_pad_get_type (),
+    "name", name, "direction", GST_PAD_SRC, NULL));
+
+  if (!gst_ghost_pad_construct (GST_GHOST_PAD (pad))) {
+    gst_object_unref (pad);
+    return NULL;
+  }
+
+  return pad;
+}
+
 struct _GstWpeSrc
 {
   GstBin parent;
 
+  GstAllocator *fd_allocator;
   GstElement *video_src;
+  GHashTable *audio_src_pads;
+  GstFlowCombiner *flow_combiner;
 };
 
 enum
@@ -54,12 +99,15 @@ static guint gst_wpe_video_src_signals[LAST_SIGNAL] = { 0 };
 
 static void gst_wpe_src_uri_handler_init (gpointer iface, gpointer data);
 
+GST_DEBUG_CATEGORY_EXTERN (wpe_src_debug);
+#define GST_CAT_DEFAULT wpe_src_debug
+
 #define gst_wpe_src_parent_class parent_class
 G_DEFINE_TYPE_WITH_CODE (GstWpeSrc, gst_wpe_src, GST_TYPE_BIN,
     G_IMPLEMENT_INTERFACE (GST_TYPE_URI_HANDLER, gst_wpe_src_uri_handler_init));
 
 static GstStaticPadTemplate video_src_factory =
-GST_STATIC_PAD_TEMPLATE ("video_src", GST_PAD_SRC, GST_PAD_ALWAYS,
+GST_STATIC_PAD_TEMPLATE ("video", GST_PAD_SRC, GST_PAD_SOMETIMES,
     GST_STATIC_CAPS ("video/x-raw(memory:GLMemory), "
                      "format = (string) RGBA, "
                      "width = " GST_VIDEO_SIZE_RANGE ", "
@@ -77,6 +125,166 @@ GST_STATIC_PAD_TEMPLATE ("video_src", GST_PAD_SRC, GST_PAD_ALWAYS,
 #endif
                      ));
 
+static GstStaticPadTemplate audio_src_factory =
+GST_STATIC_PAD_TEMPLATE ("audio_%u", GST_PAD_SRC, GST_PAD_SOMETIMES,
+    GST_STATIC_CAPS ( \
+        GST_AUDIO_CAPS_MAKE (GST_AUDIO_NE (F32)) ", layout=(string)interleaved; " \
+        GST_AUDIO_CAPS_MAKE (GST_AUDIO_NE (F64)) ", layout=(string)interleaved; " \
+        GST_AUDIO_CAPS_MAKE (GST_AUDIO_NE (S16)) ", layout=(string)interleaved" \
+));
+
+static GstFlowReturn
+gst_wpe_src_chain_buffer (GstPad * pad, GstObject * parent, GstBuffer * buffer)
+{
+  GstWpeSrc *src = GST_WPE_SRC (gst_object_get_parent (parent));
+  GstFlowReturn result, chain_result;
+
+  chain_result = gst_proxy_pad_chain_default (pad, GST_OBJECT_CAST (src), buffer);
+  result = gst_flow_combiner_update_pad_flow (src->flow_combiner, pad, chain_result);
+  gst_object_unref (src);
+
+  if (result == GST_FLOW_FLUSHING)
+    return chain_result;
+
+  return result;
+}
+
+static void
+on_audio_receiver_handle_start(void* data, uint32_t id, int32_t channels, const char* format, int32_t sampleRate)
+{
+  GstWpeSrc* src = GST_WPE_SRC (data);
+  GstWpeAudioPad *audio_pad;
+  GstPad *pad;
+  gchar *name;
+  GstEvent *stream_start;
+  GstSegment segment;
+  GstCaps *caps;
+
+  GST_DEBUG_OBJECT (src, "Exposing audio pad for stream %u", id);
+  name = g_strdup_printf ("audio_%u", id);
+  audio_pad = gst_wpe_audio_pad_new (name);
+  pad = GST_PAD_CAST (audio_pad);
+  g_free (name);
+
+  gst_pad_set_active (pad, TRUE);
+  gst_element_add_pad (GST_ELEMENT_CAST (src), pad);
+  gst_flow_combiner_add_pad (src->flow_combiner, pad);
+
+  name = gst_pad_create_stream_id_printf(pad, GST_ELEMENT_CAST (src), "%03u", id);
+  stream_start = gst_event_new_stream_start (name);
+  gst_pad_push_event (pad, stream_start);
+  g_free (name);
+
+  caps = gst_caps_new_simple ("audio/x-raw", "format", G_TYPE_STRING, format,
+    "rate", G_TYPE_INT, sampleRate,
+    "channels", G_TYPE_INT, channels,
+    "channel-mask", GST_TYPE_BITMASK, gst_audio_channel_get_fallback_mask (channels),
+    "layout", G_TYPE_STRING, "interleaved", NULL);
+  gst_audio_info_from_caps (&audio_pad->info, caps);
+  gst_pad_push_event (pad, gst_event_new_caps (caps));
+  gst_caps_unref (caps);
+
+  gst_segment_init (&segment, GST_FORMAT_TIME);
+  gst_pad_push_event (pad, gst_event_new_segment (&segment));
+
+  g_hash_table_insert (src->audio_src_pads, GUINT_TO_POINTER (id), audio_pad);
+}
+
+static void
+on_audio_receiver_handle_packet(void* data, struct wpe_audio_packet_export* packet_export, uint32_t id, int32_t fd, uint32_t size)
+{
+  GstWpeSrc* src = GST_WPE_SRC (data);
+  GstWpeAudioPad *audio_pad = GST_WPE_AUDIO_PAD (g_hash_table_lookup (src->audio_src_pads, GUINT_TO_POINTER (id)));
+  GstPad *pad = GST_PAD_CAST (audio_pad);
+  GstBuffer *buffer;
+  GstClock *clock;
+
+  g_return_if_fail (GST_IS_PAD (pad));
+  g_return_if_fail (fd >= 0);
+
+  GST_TRACE_OBJECT (pad, "Handling incoming audio packet");
+  buffer = gst_buffer_new ();
+
+  GstMemory *mem = gst_fd_allocator_alloc (src->fd_allocator, dup (fd), size, GST_FD_MEMORY_FLAG_KEEP_MAPPED);
+  gst_buffer_append_memory (buffer, mem);
+  gst_buffer_add_audio_meta (buffer, &audio_pad->info, size, NULL);
+
+  clock = gst_element_get_clock (GST_ELEMENT_CAST (src));
+  if (clock) {
+    GstClockTime now;
+    GstClockTime base_time = gst_element_get_base_time (GST_ELEMENT_CAST (src));
+
+    now = gst_clock_get_time (clock);
+    if (now > base_time)
+      now -= base_time;
+    else
+      now = 0;
+    gst_object_unref (clock);
+
+    audio_pad->buffer_time = now;
+    GST_BUFFER_DTS (buffer) = audio_pad->buffer_time;
+  }
+
+  GST_BUFFER_FLAG_UNSET (buffer, GST_BUFFER_FLAG_DISCONT);
+  if (audio_pad->discont_pending) {
+    GST_BUFFER_FLAG_SET (buffer, GST_BUFFER_FLAG_DISCONT);
+    audio_pad->discont_pending = FALSE;
+  }
+
+  gst_flow_combiner_update_pad_flow (src->flow_combiner, pad, gst_pad_push (pad, buffer));
+  wpe_audio_packet_export_release (packet_export);
+  close (fd);
+}
+
+static void
+on_audio_receiver_handle_stop(void* data, uint32_t id)
+{
+  GstWpeSrc* src = GST_WPE_SRC (data);
+  GstWpeAudioPad *audio_pad = GST_WPE_AUDIO_PAD (g_hash_table_lookup (src->audio_src_pads, GUINT_TO_POINTER (id)));
+  GstPad *pad = GST_PAD_CAST (audio_pad);
+  g_return_if_fail (GST_IS_PAD (pad));
+
+  GST_INFO_OBJECT(pad, "Stopping");
+  gst_pad_push_event (pad, gst_event_new_eos ());
+  gst_element_remove_pad (GST_ELEMENT_CAST (src), pad);
+  gst_flow_combiner_remove_pad (src->flow_combiner, pad);
+  g_hash_table_remove (src->audio_src_pads, GUINT_TO_POINTER (id));
+}
+
+static void
+on_audio_receiver_handle_pause(void* data, uint32_t id)
+{
+  GstWpeSrc* src = GST_WPE_SRC (data);
+  GstWpeAudioPad *audio_pad = GST_WPE_AUDIO_PAD (g_hash_table_lookup (src->audio_src_pads, GUINT_TO_POINTER (id)));
+  GstPad *pad = GST_PAD_CAST (audio_pad);
+  g_return_if_fail (GST_IS_PAD (pad));
+
+  GST_INFO_OBJECT(pad, "Pausing");
+  gst_pad_push_event (pad, gst_event_new_gap (audio_pad->buffer_time, GST_CLOCK_TIME_NONE));
+
+  audio_pad->discont_pending = TRUE;
+}
+
+static void
+on_audio_receiver_handle_resume(void* data, uint32_t id)
+{
+  GstWpeSrc* src = GST_WPE_SRC (data);
+  GstWpeAudioPad *audio_pad = GST_WPE_AUDIO_PAD (g_hash_table_lookup (src->audio_src_pads, GUINT_TO_POINTER (id)));
+  GstPad *pad = GST_PAD_CAST (audio_pad);
+  g_return_if_fail (GST_IS_PAD (pad));
+
+  GST_INFO_OBJECT(pad, "Resuming");
+}
+
+
+static const struct wpe_audio_receiver audio_receiver = {
+  .handle_start = on_audio_receiver_handle_start,
+  .handle_packet = on_audio_receiver_handle_packet,
+  .handle_stop = on_audio_receiver_handle_stop,
+  .handle_pause = on_audio_receiver_handle_pause,
+  .handle_resume = on_audio_receiver_handle_resume
+};
+
 static void
 gst_wpe_src_load_bytes (GstWpeVideoSrc * src, GBytes * bytes)
 {
@@ -87,6 +295,37 @@ gst_wpe_src_load_bytes (GstWpeVideoSrc * src, GBytes * bytes)
 }
 
 static void
+gst_wpe_src_set_location (GstWpeSrc * src, const gchar * location)
+{
+  GstPad *pad;
+  GstPad *ghost_pad;
+  GstProxyPad *proxy_pad;
+
+  g_object_set (src->video_src, "location", location, NULL);
+
+  ghost_pad = gst_element_get_static_pad (GST_ELEMENT_CAST (src), "video");
+  if (GST_IS_PAD (ghost_pad)) {
+    gst_object_unref (ghost_pad);
+    return;
+  }
+
+  gst_bin_add (GST_BIN_CAST (src), src->video_src);
+
+  pad = gst_element_get_static_pad (GST_ELEMENT_CAST (src->video_src), "src");
+  ghost_pad = gst_ghost_pad_new_from_template ("video", pad,
+    gst_static_pad_template_get (&video_src_factory));
+  proxy_pad = gst_proxy_pad_get_internal (GST_PROXY_PAD (ghost_pad));
+  gst_pad_set_active (GST_PAD_CAST (proxy_pad), TRUE);
+
+  gst_element_add_pad (GST_ELEMENT_CAST (src), GST_PAD_CAST (ghost_pad));
+  gst_flow_combiner_add_pad (src->flow_combiner, GST_PAD_CAST (ghost_pad));
+  gst_pad_set_chain_function (GST_PAD_CAST (proxy_pad), gst_wpe_src_chain_buffer);
+
+  gst_object_unref (proxy_pad);
+  gst_object_unref (pad);
+}
+
+static void
 gst_wpe_src_get_property (GObject * object, guint prop_id,
     GValue * value, GParamSpec * pspec)
 {
@@ -102,8 +341,12 @@ gst_wpe_src_set_property (GObject * object, guint prop_id,
 {
   GstWpeSrc *self = GST_WPE_SRC (object);
 
-  if (self->video_src)
-    g_object_set_property (G_OBJECT (self->video_src), pspec->name, value);
+  if (self->video_src) {
+    if (prop_id == PROP_LOCATION)
+      gst_wpe_src_set_location (self, g_value_get_string (value));
+    else
+      g_object_set_property (G_OBJECT (self->video_src), pspec->name, value);
+  }
 }
 
 static GstURIType
@@ -134,7 +377,7 @@ gst_wpe_src_set_uri (GstURIHandler * handler, const gchar * uri,
 {
   GstWpeSrc *src = GST_WPE_SRC (handler);
 
-  g_object_set (src->video_src, "location", uri + 6, NULL);
+  gst_wpe_src_set_location(src, uri + 6);
   return TRUE;
 }
 
@@ -152,23 +395,49 @@ gst_wpe_src_uri_handler_init (gpointer iface_ptr, gpointer data)
 static void
 gst_wpe_src_init (GstWpeSrc * src)
 {
+  gst_bin_set_suppressed_flags (GST_BIN_CAST (src),
+      static_cast<GstElementFlags>(GST_ELEMENT_FLAG_SOURCE | GST_ELEMENT_FLAG_SINK));
+  GST_OBJECT_FLAG_SET (src, GST_ELEMENT_FLAG_SOURCE);
+
+  src->fd_allocator = gst_fd_allocator_new ();
+  src->audio_src_pads = g_hash_table_new (g_direct_hash, g_direct_equal);
+  src->flow_combiner = gst_flow_combiner_new ();
   src->video_src = gst_element_factory_make ("wpevideosrc", NULL);
 
-  gst_bin_add (GST_BIN_CAST (src), src->video_src);
+  gst_wpe_video_src_register_audio_receiver (src->video_src, &audio_receiver, src);
+}
 
-  GstPad *pad =
-      gst_element_get_static_pad (GST_ELEMENT_CAST (src->video_src), "src");
+static GstStateChangeReturn
+gst_wpe_src_change_state (GstElement * element, GstStateChange transition)
+{
+  GstStateChangeReturn result;
+  GstWpeSrc *src = GST_WPE_SRC (element);
+
+  GST_DEBUG_OBJECT (src, "%s", gst_state_change_get_name (transition));
+  result = GST_CALL_PARENT_WITH_DEFAULT (GST_ELEMENT_CLASS , change_state, (element, transition), GST_STATE_CHANGE_FAILURE);
+
+  switch (transition) {
+  case GST_STATE_CHANGE_PAUSED_TO_READY:{
+    gst_flow_combiner_reset (src->flow_combiner);
+    break;
+  }
+  default:
+    break;
+  }
+
+  return result;
+}
 
-  GstPad *ghost_pad = gst_ghost_pad_new_from_template ("video_src", pad,
-      gst_static_pad_template_get (&video_src_factory));
-  GstProxyPad *proxy_pad =
-      gst_proxy_pad_get_internal (GST_PROXY_PAD (ghost_pad));
-  gst_pad_set_active (GST_PAD_CAST (proxy_pad), TRUE);
-  gst_object_unref (proxy_pad);
+static void
+gst_wpe_src_dispose (GObject *object)
+{
+    GstWpeSrc *src = GST_WPE_SRC (object);
 
-  gst_element_add_pad (GST_ELEMENT_CAST (src), GST_PAD_CAST (ghost_pad));
+    g_hash_table_unref (src->audio_src_pads);
+    gst_flow_combiner_free (src->flow_combiner);
+    gst_object_unref (src->fd_allocator);
 
-  gst_object_unref (pad);
+    GST_CALL_PARENT (G_OBJECT_CLASS, dispose, (object));
 }
 
 static void
@@ -179,6 +448,7 @@ gst_wpe_src_class_init (GstWpeSrcClass * klass)
 
   gobject_class->set_property = gst_wpe_src_set_property;
   gobject_class->get_property = gst_wpe_src_get_property;
+  gobject_class->dispose = gst_wpe_src_dispose;
 
   g_object_class_install_property (gobject_class, PROP_LOCATION,
       g_param_spec_string ("location", "location", "The URL to display", "",
@@ -189,7 +459,7 @@ gst_wpe_src_class_init (GstWpeSrcClass * klass)
           (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
 
   gst_element_class_set_static_metadata (element_class, "WPE source",
-      "Source/Video", "Creates a video stream from a WPE browser",
+      "Source/Video/Audio", "Creates a video stream from a WPE browser",
       "Philippe Normand <philn@igalia.com>, Žan Doberšek "
       "<zdobersek@igalia.com>");
 
@@ -206,10 +476,8 @@ gst_wpe_src_class_init (GstWpeSrcClass * klass)
       G_CALLBACK (gst_wpe_src_load_bytes), NULL, NULL, NULL, G_TYPE_NONE, 1,
       G_TYPE_BYTES);
 
-  gst_element_class_set_static_metadata (element_class, "WPE source",
-      "Source/Video", "Creates a video stream from a WPE browser",
-      "Philippe Normand <philn@igalia.com>, Žan Doberšek "
-      "<zdobersek@igalia.com>");
+  element_class->change_state = GST_DEBUG_FUNCPTR (gst_wpe_src_change_state);
 
   gst_element_class_add_static_pad_template (element_class, &video_src_factory);
+  gst_element_class_add_static_pad_template (element_class, &audio_src_factory);
 }
diff --git a/ext/wpe/gstwpesrcbin.h b/ext/wpe/gstwpesrcbin.h
index 87b0aea21..c61505d61 100644
--- a/ext/wpe/gstwpesrcbin.h
+++ b/ext/wpe/gstwpesrcbin.h
@@ -1,5 +1,5 @@
-/* Copyright (C) <2018> Philippe Normand <philn@igalia.com>
- * Copyright (C) <2018> Žan Doberšek <zdobersek@igalia.com>
+/* Copyright (C) <2018, 2019> Philippe Normand <philn@igalia.com>
+ * Copyright (C) <2018, 2019> Žan Doberšek <zdobersek@igalia.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -21,9 +21,36 @@
 #pragma once
 
 #include <gst/gst.h>
+#include <gst/audio/audio.h>
 
 G_BEGIN_DECLS
 
+GType gst_wpe_audio_pad_get_type(void);
+#define GST_TYPE_WPE_AUDIO_PAD            (gst_wpe_audio_pad_get_type())
+#define GST_WPE_AUDIO_PAD(obj)            (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_WPE_AUDIO_PAD,GstWpeAudioPad))
+#define GST_IS_WPE_AUDIO_PAD(obj)         (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_WPE_AUDIO_PAD))
+#define GST_WPE_AUDIO_PAD_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST((klass) ,GST_TYPE_WPE_AUDIO_PAD,GstWpeAudioPadClass))
+#define GST_IS_WPE_AUDIO_PAD_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass) ,GST_TYPE_WPE_AUDIO_PAD))
+#define GST_WPE_AUDIO_PAD_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS((obj) ,GST_TYPE_WPE_AUDIO_PAD,GstWpeAudioPadClass))
+
+typedef struct _GstWpeAudioPad GstWpeAudioPad;
+typedef struct _GstWpeAudioPadClass GstWpeAudioPadClass;
+
+struct _GstWpeAudioPad
+{
+  GstGhostPad      parent;
+
+  GstAudioInfo     info;
+  GstClockTime     buffer_time;
+  gboolean         discont_pending;
+};
+
+struct _GstWpeAudioPadClass
+{
+  GstGhostPadClass parent_class;
+};
+
+
 #define GST_TYPE_WPE_SRC            (gst_wpe_src_get_type())
 #define GST_WPE_SRC(obj)            (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_WPE_SRC,GstWpeSrc))
 #define GST_WPE_SRC_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST((klass), GST_TYPE_WPE_SRC,GstWpeSrcClass))
diff --git a/ext/wpe/gstwpevideosrc.cpp b/ext/wpe/gstwpevideosrc.cpp
index 7d7556fb5..ca5fc59ec 100644
--- a/ext/wpe/gstwpevideosrc.cpp
+++ b/ext/wpe/gstwpevideosrc.cpp
@@ -86,6 +86,7 @@
 #endif
 
 #include "gstwpevideosrc.h"
+#include "gstwpe-private.h"
 #include <gst/gl/gl.h>
 #include <gst/gl/egl/gstglmemoryegl.h>
 #include <gst/gl/wayland/gstgldisplay_wayland.h>
@@ -128,6 +129,8 @@ struct _GstWpeVideoSrc
   gint64 n_frames;              /* total frames sent */
 
   WPEView *view;
+  const struct wpe_audio_receiver *audio_receiver;
+  gpointer audio_receiver_data;
 
   GMutex lock;
 };
@@ -296,6 +299,11 @@ gst_wpe_video_src_start (GstWpeVideoSrc * src)
 
   if (created_view) {
     src->n_frames = 0;
+    if (src->audio_receiver) {
+      src->view->registerAudioReceiver(src->audio_receiver, src->audio_receiver_data);
+      src->audio_receiver = NULL,
+      src->audio_receiver_data = NULL;
+    }
   }
   WPE_UNLOCK (src);
   return TRUE;
@@ -735,4 +743,17 @@ gst_wpe_video_src_class_init (GstWpeVideoSrcClass * klass)
       static_cast < GSignalFlags > (G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION),
       G_CALLBACK (gst_wpe_video_src_load_bytes), NULL, NULL, NULL,
       G_TYPE_NONE, 1, G_TYPE_BYTES);
+}
+
+void
+gst_wpe_video_src_register_audio_receiver(GstElement* video_src, const struct wpe_audio_receiver* receiver, gpointer user_data)
+{
+  GstWpeVideoSrc* src = GST_WPE_VIDEO_SOURCE(video_src);
+
+  if (!src->view) {
+    src->audio_receiver = receiver;
+    src->audio_receiver_data = user_data;
+    return;
+  }
+  src->view->registerAudioReceiver(receiver, user_data);
 }
\ No newline at end of file
diff --git a/ext/wpe/meson.build b/ext/wpe/meson.build
index 96b30a99a..580d6649c 100644
--- a/ext/wpe/meson.build
+++ b/ext/wpe/meson.build
@@ -18,7 +18,7 @@ endif
 
 gstwpe = library('gstwpe',
   ['WPEThreadedView.cpp', 'gstwpe.cpp', 'gstwpevideosrc.cpp', 'gstwpesrcbin.cpp'],
-  dependencies : [egl_dep, wpe_dep, wpe_fdo_dep, gstvideo_dep, gstbase_dep, gstgl_dep, xkbcommon_dep, wl_server_dep],
+  dependencies : [egl_dep, wpe_dep, wpe_fdo_dep, gstallocators_dep, gstaudio_dep, gstvideo_dep, gstbase_dep, gstgl_dep, xkbcommon_dep, wl_server_dep],
   cpp_args : gst_plugins_bad_args + ['-DHAVE_CONFIG_H=1'],
   include_directories : [configinc],
   install : true,