Bug 959007 - Firefox crashes when starting html5 web player. r=cpearce, r=edwin

content/media/gstreamer/GStreamerFunctionList.h

@@ -60,6 +60,7 @@ GST_FUNC(LIBGSTREAMER, gst_mini_object_get_type)
 GST_FUNC(LIBGSTREAMER, gst_mini_object_new)
 GST_FUNC(LIBGSTREAMER, gst_mini_object_ref)
 GST_FUNC(LIBGSTREAMER, gst_mini_object_unref)
+GST_FUNC(LIBGSTREAMER, gst_object_get_name)
 GST_FUNC(LIBGSTREAMER, gst_object_get_parent)
 GST_FUNC(LIBGSTREAMER, gst_object_unref)
 GST_FUNC(LIBGSTREAMER, gst_pad_add_event_probe)

content/media/gstreamer/GStreamerReader.cpp

@@ -175,6 +175,8 @@ nsresult GStreamerReader::Init(MediaDecoderReader* aCloneDonor)
 
   g_signal_connect(G_OBJECT(mPlayBin), "notify::source",
                    G_CALLBACK(GStreamerReader::PlayBinSourceSetupCb), this);
+  g_signal_connect(G_OBJECT(mPlayBin), "element-added",
+                   G_CALLBACK(GStreamerReader::PlayElementAddedCb), this);
 
   return NS_OK;
 }
@@ -921,6 +923,11 @@ GstFlowReturn GStreamerReader::AllocateVideoBufferFull(GstPad* aPad,
 {
   /* allocate an image using the container */
   ImageContainer* container = mDecoder->GetImageContainer();
+  if (!container) {
+    // We don't have an ImageContainer. We probably belong to an <audio>
+    // element.
+    return GST_FLOW_NOT_SUPPORTED;
+  }
   PlanarYCbCrImage* img =
     reinterpret_cast<PlanarYCbCrImage*>(
       container->CreateImage(ImageFormat::PLANAR_YCBCR).get());
@@ -1068,6 +1075,76 @@ void GStreamerReader::Eos()
   }
 }
 
+/**
+ * This callback is called while the pipeline is automatically built, after a
+ * new element has been added to the pipeline. We use it to find the
+ * uridecodebin instance used by playbin and connect to it to apply our
+ * whitelist.
+ */
+void
+GStreamerReader::PlayElementAddedCb(GstBin *aBin, GstElement *aElement,
+                                    gpointer *aUserData)
+{
+  const static char sUriDecodeBinPrefix[] = "uridecodebin";
+  gchar *name = gst_element_get_name(aElement);
+
+  // Attach this callback to uridecodebin, child of playbin.
+  if (!strncmp(name, sUriDecodeBinPrefix, sizeof(sUriDecodeBinPrefix) - 1)) {
+    g_signal_connect(G_OBJECT(aElement), "autoplug-sort",
+                     G_CALLBACK(GStreamerReader::AutoplugSortCb), aUserData);
+  }
+
+  g_free(name);
+}
+
+bool
+GStreamerReader::ShouldAutoplugFactory(GstElementFactory* aFactory, GstCaps* aCaps)
+{
+  bool autoplug;
+  const gchar *klass = gst_element_factory_get_klass(aFactory);
+  if (strstr(klass, "Demuxer") && !strstr(klass, "Metadata")) {
+    autoplug = GStreamerFormatHelper::Instance()->CanHandleContainerCaps(aCaps);
+  } else if (strstr(klass, "Decoder") && !strstr(klass, "Generic")) {
+    autoplug = GStreamerFormatHelper::Instance()->CanHandleCodecCaps(aCaps);
+  } else {
+    /* we only filter demuxers and decoders, let everything else be autoplugged */
+    autoplug = true;
+  }
+
+  return autoplug;
+}
+
+/**
+ * This is called by uridecodebin (running inside playbin), after it has found
+ * candidate factories to continue decoding the stream. We apply the whitelist
+ * here, allowing only demuxers and decoders that output the formats we want to
+ * support.
+ */
+GValueArray*
+GStreamerReader::AutoplugSortCb(GstElement* aElement, GstPad* aPad,
+                                GstCaps* aCaps, GValueArray* aFactories)
+{
+  if (!aFactories->n_values) {
+    return nullptr;
+  }
+
+  /* aFactories[0] is the element factory that is going to be used to
+   * create the next element needed to demux or decode the stream.
+   */
+  GstElementFactory *factory = (GstElementFactory*) g_value_get_object(g_value_array_get_nth(aFactories, 0));
+  if (!ShouldAutoplugFactory(factory, aCaps)) {
+    /* We don't support this factory. Return an empty array to signal that we
+     * don't want to continue decoding this (sub)stream.
+     */
+    return g_value_array_new(0);
+  }
+
+  /* nullptr means that we're ok with the candidates and don't need to apply any
+   * sorting/filtering.
+   */
+  return nullptr;
+}
+
 /**
  * If this is an MP3 stream, pass any new data we get to the MP3 frame parser
  * for duration estimation.

content/media/gstreamer/GStreamerReader.h

@@ -136,6 +136,23 @@ private:
   static void EosCb(GstAppSink* aSink, gpointer aUserData);
   void Eos();
 
+  /* Called when an element is added inside playbin. We use it to find the
+   * decodebin instance.
+   */
+  static void PlayElementAddedCb(GstBin *aBin, GstElement *aElement,
+                                 gpointer *aUserData);
+
+  /* Called during decoding, to decide whether a (sub)stream should be decoded or
+   * ignored */
+  static bool ShouldAutoplugFactory(GstElementFactory* aFactory, GstCaps* aCaps);
+
+  /* Called by decodebin during autoplugging. We use it to apply our
+   * container/codec whitelist.
+   */
+  static GValueArray* AutoplugSortCb(GstElement* aElement,
+                                     GstPad* aPad, GstCaps* aCaps,
+                                     GValueArray* aFactories);
+
   // Try to find MP3 headers in this stream using our MP3 frame parser.
   nsresult ParseMP3Headers();