--- a/dom/media/DecoderDoctorDiagnostics.cpp
+++ b/dom/media/DecoderDoctorDiagnostics.cpp
@@ -285,41 +285,64 @@ DecoderDoctorDocumentWatcher::ReportAnal
   nsContentUtils::ReportToConsole(nsIScriptError::warningFlag,
                                   NS_LITERAL_CSTRING("Media"),
                                   mDocument,
                                   nsContentUtils::eDOM_PROPERTIES,
                                   aReportStringId,
                                   params,
                                   ArrayLength(params));
 
-  DispatchNotification(mDocument->GetInnerWindow(), aNotificationType, aFormats);
+  // For now, disable all front-end notifications by default.
+  // TODO: Future bugs will use finer-grained filtering instead.
+  if (Preferences::GetBool("media.decoderdoctor.enable-notification-bar", false)) {
+    DispatchNotification(
+      mDocument->GetInnerWindow(), aNotificationType, aFormats);
+  }
 }
 
 void
 DecoderDoctorDocumentWatcher::SynthesizeAnalysis()
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   bool canPlay = false;
+#if defined(MOZ_FFMPEG)
+  bool PlatformDecoderNeeded = false;
+#endif
   nsAutoString formats;
   for (auto& diag : mDiagnosticsSequence) {
     if (diag.mDecoderDoctorDiagnostics.CanPlay()) {
       canPlay = true;
     } else {
+#if defined(MOZ_FFMPEG)
+      if (diag.mDecoderDoctorDiagnostics.DidFFmpegFailToLoad()) {
+        PlatformDecoderNeeded = true;
+      }
+#endif
       if (!formats.IsEmpty()) {
         formats += NS_LITERAL_STRING(", ");
       }
       formats += diag.mFormat;
     }
   }
   if (!canPlay) {
-    DD_WARN("DecoderDoctorDocumentWatcher[%p, doc=%p]::Notify() - Cannot play media, formats: %s",
-            this, mDocument, NS_ConvertUTF16toUTF8(formats).get());
-    ReportAnalysis(dom::DecoderDoctorNotificationType::Cannot_play,
-                   "MediaCannotPlayNoDecoders", formats);
+#if defined(MOZ_FFMPEG)
+    if (PlatformDecoderNeeded) {
+      DD_DEBUG("DecoderDoctorDocumentWatcher[%p, doc=%p]::Notify() - formats: %s -> Cannot play media because platform decoder was not found",
+               this, mDocument, NS_ConvertUTF16toUTF8(formats).get());
+      ReportAnalysis(dom::DecoderDoctorNotificationType::Platform_decoder_not_found,
+                     "MediaPlatformDecoderNotFound", formats);
+    } else
+#endif
+    {
+      DD_WARN("DecoderDoctorDocumentWatcher[%p, doc=%p]::Notify() - Cannot play media, formats: %s",
+              this, mDocument, NS_ConvertUTF16toUTF8(formats).get());
+      ReportAnalysis(dom::DecoderDoctorNotificationType::Cannot_play,
+                     "MediaCannotPlayNoDecoders", formats);
+    }
   } else if (!formats.IsEmpty()) {
     DD_INFO("DecoderDoctorDocumentWatcher[%p, doc=%p]::Notify() - Can play media, but no decoders for some requested formats: %s",
             this, mDocument, NS_ConvertUTF16toUTF8(formats).get());
     if (Preferences::GetBool("media.decoderdoctor.verbose", false)) {
       ReportAnalysis(
         dom::DecoderDoctorNotificationType::Can_play_but_some_missing_decoders,
         "MediaNoDecoders", formats);
     }
@@ -335,19 +358,19 @@ DecoderDoctorDocumentWatcher::AddDiagnos
                                             DecoderDoctorDiagnostics&& aDiagnostics)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   if (!mDocument) {
     return;
   }
 
-  DD_DEBUG("DecoderDoctorDocumentWatcher[%p, doc=%p]::AddDiagnostics(format='%s', call site '%s', can play=%d)",
+  DD_DEBUG("DecoderDoctorDocumentWatcher[%p, doc=%p]::AddDiagnostics(format='%s', call site '%s', can play=%d, platform lib failed to load=%d)",
            this, mDocument, NS_ConvertUTF16toUTF8(aFormat).get(),
-           aCallSite, aDiagnostics.CanPlay());
+           aCallSite, aDiagnostics.CanPlay(), aDiagnostics.DidFFmpegFailToLoad());
   mDiagnosticsSequence.AppendElement(
     Diagnostics(Move(aDiagnostics), aFormat, aCallSite));
   EnsureTimerIsStarted();
 }
 
 NS_IMETHODIMP
 DecoderDoctorDocumentWatcher::Notify(nsITimer* timer)
 {

--- a/dom/media/DecoderDoctorDiagnostics.h
+++ b/dom/media/DecoderDoctorDiagnostics.h
@@ -39,16 +39,21 @@ public:
                         const nsAString& aFormat,
                         const char* aCallSite);
 
   // Methods to record diagnostic information:
 
   void SetCanPlay() { mCanPlay = true; }
   bool CanPlay() const { return mCanPlay; }
 
+  void SetFFmpegFailedToLoad() { mFFmpegFailedToLoad = true; }
+  bool DidFFmpegFailToLoad() const { return mFFmpegFailedToLoad; }
+
 private:
   // True if there is at least one decoder that can play the media.
   bool mCanPlay = false;
+
+  bool mFFmpegFailedToLoad = false;
 };
 
 } // namespace mozilla
 
 #endif

--- a/dom/media/platforms/PDMFactory.cpp
+++ b/dom/media/platforms/PDMFactory.cpp
@@ -37,16 +37,18 @@
 
 #include "AgnosticDecoderModule.h"
 
 #ifdef MOZ_EME
 #include "EMEDecoderModule.h"
 #include "mozilla/CDMProxy.h"
 #endif
 
+#include "DecoderDoctorDiagnostics.h"
+
 namespace mozilla {
 
 extern already_AddRefed<PlatformDecoderModule> CreateAgnosticDecoderModule();
 extern already_AddRefed<PlatformDecoderModule> CreateBlankDecoderModule();
 
 bool PDMFactory::sUseBlankDecoder = false;
 #ifdef MOZ_GONK_MEDIACODEC
 bool PDMFactory::sGonkDecoderEnabled = false;
@@ -155,16 +157,24 @@ PDMFactory::CreateDecoder(const TrackInf
                                 aConfig,
                                 aTaskQueue,
                                 aCallback,
                                 aDiagnostics,
                                 aLayersBackend,
                                 aImageContainer);
   }
 
+  if (aDiagnostics) {
+    // If libraries failed to load, the following loop over mCurrentPDMs
+    // will not even try to use them. So we record failures now.
+    if (mFFmpegFailedToLoad) {
+      aDiagnostics->SetFFmpegFailedToLoad();
+    }
+  }
+
   for (auto& current : mCurrentPDMs) {
     if (!current->SupportsMimeType(aConfig.mMimeType, aDiagnostics)) {
       continue;
     }
     RefPtr<MediaDataDecoder> m =
       CreateDecoderWithPDM(current,
                            aConfig,
                            aTaskQueue,
@@ -287,17 +297,19 @@ PDMFactory::CreatePDMs()
   if (sFFVPXDecoderEnabled) {
     m = FFVPXRuntimeLinker::CreateDecoderModule();
     StartupPDM(m);
   }
 #endif
 #ifdef MOZ_FFMPEG
   if (sFFmpegDecoderEnabled) {
     m = FFmpegRuntimeLinker::CreateDecoderModule();
-    StartupPDM(m);
+    if (!StartupPDM(m)) {
+      mFFmpegFailedToLoad = true;
+    }
   }
 #endif
 #ifdef MOZ_APPLEMEDIA
   m = new AppleDecoderModule();
   StartupPDM(m);
 #endif
 #ifdef MOZ_GONK_MEDIACODEC
   if (sGonkDecoderEnabled) {
@@ -330,16 +342,24 @@ PDMFactory::StartupPDM(PlatformDecoderMo
   }
   return false;
 }
 
 already_AddRefed<PlatformDecoderModule>
 PDMFactory::GetDecoder(const nsACString& aMimeType,
                        DecoderDoctorDiagnostics* aDiagnostics) const
 {
+  if (aDiagnostics) {
+    // If libraries failed to load, the following loop over mCurrentPDMs
+    // will not even try to use them. So we record failures now.
+    if (mFFmpegFailedToLoad) {
+      aDiagnostics->SetFFmpegFailedToLoad();
+    }
+  }
+
   RefPtr<PlatformDecoderModule> pdm;
   for (auto& current : mCurrentPDMs) {
     if (current->SupportsMimeType(aMimeType, aDiagnostics)) {
       pdm = current;
       break;
     }
   }
   return pdm.forget();

--- a/dom/media/platforms/PDMFactory.h
+++ b/dom/media/platforms/PDMFactory.h
@@ -89,13 +89,15 @@ private:
   static bool sWMFDecoderEnabled;
 #endif
   static bool sEnableFuzzingWrapper;
   static uint32_t sVideoOutputMinimumInterval_ms;
   static bool sDontDelayInputExhausted;
 
   nsTArray<RefPtr<PlatformDecoderModule>> mCurrentPDMs;
   RefPtr<PlatformDecoderModule> mEMEPDM;
+
+  bool mFFmpegFailedToLoad = false;
 };
 
 } // namespace mozilla
 
 #endif /* PDMFactory_h_ */