Bug 1552145 - Make MediaChangeMonitor by default not try to init deco…

…der until it receives extradata. r=jya

In bug 1538508 we changed the MediaChangeMonitor to raise an error when we try
to create a decoder and we don't yet have the H.264 extra data, to maintain the
assumptions made by OpenH264/WebRTC. This however doesn't play nice with the
HLS demuxer, which won't always give you extra data after a seek.

So change the MediaChangeMonitor to by default assume that it should just drop
frames until it has the extra data it needs to create a decoder. We can flag
this mode off in the WebRTC MediaDataDecoder.

Differential Revision: https://phabricator.services.mozilla.com/D34079

dom/media/platforms/PlatformDecoderModule.h

@@ -49,6 +49,10 @@ struct MOZ_STACK_CLASS CreateDecoderParams final {
     LowLatency,
     HardwareDecoderNotAllowed,
     FullH264Parsing,
+    ErrorIfNoInitializationData,  // By default frames delivered before
+                                  // initialization data are dropped. Pass this
+                                  // option to raise an error if frames are
+                                  // delivered before initialization data.
 
     SENTINEL  // one past the last valid value
   };

dom/media/platforms/wrappers/MediaChangeMonitor.cpp

@@ -225,6 +225,8 @@ MediaChangeMonitor::MediaChangeMonitor(PlatformDecoderModule* aPDM,
       mDecoder(nullptr),
       mGMPCrashHelper(aParams.mCrashHelper),
       mLastError(NS_OK),
+      mErrorIfNoInitializationData(aParams.mOptions.contains(
+          CreateDecoderParams::Option::ErrorIfNoInitializationData)),
       mType(aParams.mType),
       mOnWaitingForKeyEvent(aParams.mOnWaitingForKeyEvent),
       mDecoderOptions(aParams.mOptions),
@@ -289,8 +291,12 @@ RefPtr<MediaDataDecoder::DecodePromise> MediaChangeMonitor::Decode(
 
     if (rv == NS_ERROR_NOT_INITIALIZED) {
       // We are missing the required init data to create the decoder.
-      // This frame can't be decoded and should be treated as an error.
-      return DecodePromise::CreateAndReject(rv, __func__);
+      if (mErrorIfNoInitializationData) {
+        // This frame can't be decoded and should be treated as an error.
+        return DecodePromise::CreateAndReject(rv, __func__);
+      }
+      // Swallow the frame, and await delivery of init data.
+      return DecodePromise::CreateAndResolve(DecodedData(), __func__);
     }
     if (rv == NS_ERROR_DOM_MEDIA_INITIALIZING_DECODER) {
       // The decoder is pending initialization.

dom/media/platforms/wrappers/MediaChangeMonitor.h

@@ -114,6 +114,7 @@ class MediaChangeMonitor : public MediaDataDecoder,
   RefPtr<GMPCrashHelper> mGMPCrashHelper;
   MediaResult mLastError;
   bool mNeedKeyframe = true;
+  const bool mErrorIfNoInitializationData;
   const TrackInfo::TrackType mType;
   MediaEventProducer<TrackInfo::TrackType>* const mOnWaitingForKeyEvent;
   const CreateDecoderParams::OptionSet mDecoderOptions;

media/webrtc/signaling/src/media-conduit/WebrtcMediaDataDecoderCodec.cpp

@@ -57,7 +57,8 @@ int32_t WebrtcMediaDataDecoder::InitDecode(
       {mInfo, mTaskQueue,
        CreateDecoderParams::OptionSet(
            CreateDecoderParams::Option::LowLatency,
-           CreateDecoderParams::Option::FullH264Parsing),
+           CreateDecoderParams::Option::FullH264Parsing,
+           CreateDecoderParams::Option::ErrorIfNoInitializationData),
        mTrackType, mImageContainer, knowsCompositor});
 
   if (!mDecoder) {