Bug 1536783 - Use two tile threads in dav1d decoder for performance improvement. r=TD-Linux

Differential Revision: https://phabricator.services.mozilla.com/D24331

--HG--
extra : moz-landing-system : lando

dom/media/platforms/agnostic/DAV1DDecoder.cpp

@@ -31,6 +31,11 @@ RefPtr<MediaDataDecoder::InitPromise> DAV1DDecoder::Init() {
   }
   settings.n_frame_threads =
       static_cast<int>(std::min(decoder_threads, GetNumberOfProcessors()));
+  // There is not much improvement with more than 2 tile threads at least with
+  // the content being currently served. The ideal number of tile thread would
+  // much the tile count of the content. Maybe dav1d can help to do that in the
+  // future.
+  settings.n_tile_threads = 2;
 
   int res = dav1d_open(&mContext, &settings);
   if (res < 0) {

dom/media/platforms/agnostic/DAV1DDecoder.h

@@ -38,7 +38,7 @@ class DAV1DDecoder : public MediaDataDecoder,
   int GetPicture(DecodedData& aData, MediaResult& aResult);
   already_AddRefed<VideoData> ConstructImage(const Dav1dPicture& aPicture);
 
-  Dav1dContext* mContext;
+  Dav1dContext* mContext = nullptr;
 
   const VideoInfo& mInfo;
   const RefPtr<TaskQueue> mTaskQueue;