--- a/dom/media/platforms/PDMFactory.cpp
+++ b/dom/media/platforms/PDMFactory.cpp
@@ -262,17 +262,17 @@ PDMFactory::CreateDecoderWithPDM(Platfor
       TimeDuration::FromMilliseconds(MediaPrefs::PDMFuzzingInterval()));
     callbackWrapper->SetDontDelayInputExhausted(!MediaPrefs::PDMFuzzingDelayInputExhausted());
     callback = callbackWrapper.get();
   }
 
   CreateDecoderParams params = aParams;
   params.mCallback = callback;
 
-  if (MP4Decoder::IsH264(config.mMimeType)) {
+  if (MP4Decoder::IsH264(config.mMimeType) && !aParams.mUseBlankDecoder) {
     RefPtr<H264Converter> h = new H264Converter(aPDM, params);
     const nsresult rv = h->GetLastError();
     if (NS_SUCCEEDED(rv) || rv == NS_ERROR_NOT_INITIALIZED) {
       // The H264Converter either successfully created the wrapped decoder,
       // or there wasn't enough AVCC data to do so. Otherwise, there was some
       // problem, for example WMF DLLs were missing.
       m = h.forget();
     }

--- a/dom/media/platforms/agnostic/BlankDecoderModule.cpp
+++ b/dom/media/platforms/agnostic/BlankDecoderModule.cpp
@@ -6,16 +6,17 @@
 
 #include "ImageContainer.h"
 #include "MediaDecoderReader.h"
 #include "MediaInfo.h"
 #include "mozilla/CheckedInt.h"
 #include "mozilla/mozalloc.h" // for operator new, and new (fallible)
 #include "mozilla/RefPtr.h"
 #include "mozilla/TaskQueue.h"
+#include "mp4_demuxer/AnnexB.h"
 #include "mp4_demuxer/H264.h"
 #include "MP4Decoder.h"
 #include "nsAutoPtr.h"
 #include "nsRect.h"
 #include "PlatformDecoderModule.h"
 #include "ReorderQueue.h"
 #include "TimeUnits.h"
 #include "VideoUtils.h"
@@ -29,17 +30,19 @@ class BlankMediaDataDecoder : public Med
 public:
 
   BlankMediaDataDecoder(BlankMediaDataCreator* aCreator,
                         const CreateDecoderParams& aParams)
     : mCreator(aCreator)
     , mCallback(aParams.mCallback)
     , mMaxRefFrames(aParams.mConfig.GetType() == TrackInfo::kVideoTrack &&
                     MP4Decoder::IsH264(aParams.mConfig.mMimeType)
-                    ? mp4_demuxer::H264::ComputeMaxRefFrames(aParams.VideoConfig().mExtraData)
+                    ? mp4_demuxer::AnnexB::HasSPS(aParams.VideoConfig().mExtraData)
+                      ? mp4_demuxer::H264::ComputeMaxRefFrames(aParams.VideoConfig().mExtraData)
+                      : 16
                     : 0)
     , mType(aParams.mConfig.GetType())
   {
   }
 
   RefPtr<InitPromise> Init() override {
     return InitPromise::CreateAndResolve(mType, __func__);
   }