Bug 1892516 - part1 : explicitly disable HEVC support to avoid running the initialization again. r=media-playback-reviewers,padenot

We can actually control whether HEVC is enabled by setting
`sForceEnableHEVC` to false without running decoder module's
initialization again, which can save some time because the
initialization is expensive.

[1] https://searchfox.org/mozilla-central/rev/ee9fd5e2df79c6d69af5aa9bc36041166f483227/dom/media/platforms/wmf/WMFDecoderModule.cpp#486

Differential Revision: https://phabricator.services.mozilla.com/D208243

dom/media/platforms/wmf/WMFDecoderModule.cpp

@@ -485,6 +485,9 @@ bool WMFDecoderModule::IsHEVCSupported() {
   return sForceEnableHEVC || StaticPrefs::media_wmf_hevc_enabled() == 1;
 }
 
+/* static */
+void WMFDecoderModule::DisableForceEnableHEVC() { sForceEnableHEVC = false; }
+
 }  // namespace mozilla
 
 #undef WFM_DECODER_MODULE_STATUS_MARKER

dom/media/platforms/wmf/WMFDecoderModule.h

@@ -10,6 +10,7 @@
 #  include "PlatformDecoderModule.h"
 #  include "WMF.h"
 #  include "WMFUtils.h"
+#  include "mozilla/Atomics.h"
 
 namespace mozilla {
 
@@ -55,11 +56,13 @@ class WMFDecoderModule : public PlatformDecoderModule {
                                   RefPtr<MFTDecoder>& aDecoder);
   static bool CanCreateMFTDecoder(const WMFStreamType& aType);
 
+  static void DisableForceEnableHEVC();
+
  private:
   // This is used for GPU process only, where we can't set the preference
   // directly (it can only set in the parent process) So we need a way to force
   // enable the HEVC in order to report the support information via telemetry.
-  static inline bool sForceEnableHEVC = false;
+  static inline Atomic<bool> sForceEnableHEVC{false};
 
   static bool IsHEVCSupported();
 

gfx/ipc/GPUParent.cpp

@@ -120,12 +120,9 @@ static void ReportHardwareMediaCodecSupportIfNeeded() {
   }
   sReported = true;
 
-  // TODO : we can remove this after HEVC is enabled by default.
-  // HEVC is not enabled. We need to force to enable it in order to know
-  // its support as well, and it would be turn off later.
-  if (StaticPrefs::media_wmf_hevc_enabled() != 1) {
-    WMFDecoderModule::Init(WMFDecoderModule::Config::ForceEnableHEVC);
-  }
+  // We will disable HVEC later after reporting Telemetry if the pref is off.
+  WMFDecoderModule::Init(WMFDecoderModule::Config::ForceEnableHEVC);
+
   const auto support = PDMFactory::Supported(true /* force refresh */);
   if (support.contains(
           mozilla::media::MediaCodecsSupport::H264HardwareDecode)) {
@@ -155,7 +152,7 @@ static void ReportHardwareMediaCodecSupportIfNeeded() {
         true);
   }
   if (StaticPrefs::media_wmf_hevc_enabled() != 1) {
-    WMFDecoderModule::Init();
+    WMFDecoderModule::DisableForceEnableHEVC();
   }
 
 #endif