--- a/dom/media/platforms/wmf/MFTDecoder.cpp
+++ b/dom/media/platforms/wmf/MFTDecoder.cpp
@@ -213,17 +213,17 @@ MFTDecoder::Output(RefPtr<IMFSample>* aO
   if (output.pEvents) {
     // We must release this, as per the IMFTransform::ProcessOutput()
     // MSDN documentation.
     output.pEvents->Release();
     output.pEvents = nullptr;
   }
 
   if (hr == MF_E_TRANSFORM_STREAM_CHANGE) {
-    // Type change, probably geometric aperature change.
+    // Type change, probably geometric aperture change.
     // Reconfigure decoder output type, so that GetOutputMediaType()
     // returns the new type, and return the error code to caller.
     // This is an expected failure, so don't warn on encountering it.
     hr = SetDecoderOutputType(nullptr, nullptr);
     NS_ENSURE_TRUE(SUCCEEDED(hr), hr);
     // Return the error, so that the caller knows to retry.
     return MF_E_TRANSFORM_STREAM_CHANGE;
   }

--- a/dom/media/platforms/wmf/WMFDecoderModule.cpp
+++ b/dom/media/platforms/wmf/WMFDecoderModule.cpp
@@ -23,16 +23,17 @@
 #include "prsystem.h"
 #include "mozilla/Maybe.h"
 
 namespace mozilla {
 
 static bool sDXVAEnabled = false;
 static int  sNumDecoderThreads = -1;
 static bool sIsIntelDecoderEnabled = false;
+static bool sLowLatencyMFTEnabled = false;
 
 WMFDecoderModule::WMFDecoderModule()
   : mWMFInitialized(false)
 {
 }
 
 WMFDecoderModule::~WMFDecoderModule()
 {
@@ -63,26 +64,34 @@ SetNumOfDecoderThreads()
 
 /* static */
 void
 WMFDecoderModule::Init()
 {
   MOZ_ASSERT(NS_IsMainThread(), "Must be on main thread.");
   sDXVAEnabled = gfxPlatform::GetPlatform()->CanUseHardwareVideoDecoding();
   sIsIntelDecoderEnabled = Preferences::GetBool("media.webm.intel_decoder.enabled", false);
+  sLowLatencyMFTEnabled = Preferences::GetBool("media.wmf.low-latency.enabled", false);
   SetNumOfDecoderThreads();
 }
 
 /* static */
 int
 WMFDecoderModule::GetNumDecoderThreads()
 {
   return sNumDecoderThreads;
 }
 
+/* static */
+bool
+WMFDecoderModule::LowLatencyMFTEnabled()
+{
+  return sLowLatencyMFTEnabled;
+}
+
 nsresult
 WMFDecoderModule::Startup()
 {
   mWMFInitialized = SUCCEEDED(wmf::MFStartup());
   return mWMFInitialized ? NS_OK : NS_ERROR_FAILURE;
 }
 
 already_AddRefed<MediaDataDecoder>

--- a/dom/media/platforms/wmf/WMFDecoderModule.h
+++ b/dom/media/platforms/wmf/WMFDecoderModule.h
@@ -36,15 +36,16 @@ public:
   ConversionRequired
   DecoderNeedsConversion(const TrackInfo& aConfig) const override;
 
   // Called on main thread.
   static void Init();
 
   // Called from any thread, must call init first
   static int GetNumDecoderThreads();
+  static bool LowLatencyMFTEnabled();
 private:
   bool mWMFInitialized;
 };
 
 } // namespace mozilla
 
 #endif

--- a/dom/media/platforms/wmf/WMFVideoMFTManager.cpp
+++ b/dom/media/platforms/wmf/WMFVideoMFTManager.cpp
@@ -211,22 +211,23 @@ WMFVideoMFTManager::InitInternal(bool aF
   NS_ENSURE_TRUE(SUCCEEDED(hr), false);
 
   RefPtr<IMFAttributes> attr(decoder->GetAttributes());
   UINT32 aware = 0;
   if (attr) {
     attr->GetUINT32(MF_SA_D3D_AWARE, &aware);
     attr->SetUINT32(CODECAPI_AVDecNumWorkerThreads,
       WMFDecoderModule::GetNumDecoderThreads());
-    hr = attr->SetUINT32(CODECAPI_AVLowLatencyMode, TRUE);
-    if (SUCCEEDED(hr)) {
-      LOG("Enabling Low Latency Mode");
-    }
-    else {
-      LOG("Couldn't enable Low Latency Mode");
+    if (WMFDecoderModule::LowLatencyMFTEnabled()) {
+      hr = attr->SetUINT32(CODECAPI_AVLowLatencyMode, TRUE);
+      if (SUCCEEDED(hr)) {
+        LOG("Enabling Low Latency Mode");
+      } else {
+        LOG("Couldn't enable Low Latency Mode");
+      }
     }
   }
 
   if (useDxva) {
     if (aware) {
       // TODO: Test if I need this anywhere... Maybe on Vista?
       //hr = attr->SetUINT32(CODECAPI_AVDecVideoAcceleration_H264, TRUE);
       //NS_ENSURE_TRUE(SUCCEEDED(hr), hr);

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -318,16 +318,17 @@ pref("media.mp4.enabled", true);
 // Specifies whether the PDMFactory can create a test decoder that
 #endif
 // just outputs blank frames/audio instead of actually decoding. The blank
 // decoder works on all platforms.
 pref("media.use-blank-decoder", false);
 #ifdef MOZ_WMF
 pref("media.wmf.enabled", true);
 pref("media.wmf.decoder.thread-count", -1);
+pref("media.wmf.low-latency.enabled", false);
 #endif
 #if defined(MOZ_FFMPEG)
 pref("media.ffmpeg.enabled", true);
 #endif
 pref("media.gmp.decoder.enabled", false);
 pref("media.gmp.decoder.aac", 0);
 pref("media.gmp.decoder.h264", 0);
 #ifdef MOZ_RAW

--- a/testing/web-platform/meta/media-source/mediasource-append-buffer.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-append-buffer.html.ini
@@ -1,5 +1,5 @@
 [mediasource-append-buffer.html]
   type: testharness
   prefs: [media.mediasource.enabled:true]
   disabled:
-    if (os == "linux") or ((os == "win") and (version == "6.1.7601")): https://bugzilla.mozilla.org/show_bug.cgi?id=1191138
+    if (os == "linux") or (os == "win"): https://bugzilla.mozilla.org/show_bug.cgi?id=1191138