Bug 1211335: Have FFMpegDecoderModule properly return if a codec is supported. r=cpearce

dom/media/platforms/ffmpeg/FFmpegDataDecoder.cpp

@@ -70,24 +70,16 @@ ChoosePixelFormat(AVCodecContext* aCodecContext, const PixelFormat* aFormats)
 nsresult
 FFmpegDataDecoder<LIBAV_VER>::InitDecoder()
 {
-  StaticMutexAutoLock mon(sMonitor);
-
   FFMPEG_LOG("Initialising FFmpeg decoder.");
 
-  if (!sFFmpegInitDone) {
-    avcodec_register_all();
-#ifdef DEBUG
-    av_log_set_level(AV_LOG_DEBUG);
-#endif
-    sFFmpegInitDone = true;
-  }
-
-  AVCodec* codec = avcodec_find_decoder(mCodecID);
+  AVCodec* codec = FindAVCodec(mCodecID);
   if (!codec) {
     NS_WARNING("Couldn't find ffmpeg decoder");
     return NS_ERROR_FAILURE;
   }
 
+  StaticMutexAutoLock mon(sMonitor);
+
   if (!(mCodecContext = avcodec_alloc_context3(codec))) {
     NS_WARNING("Couldn't init ffmpeg context");
     return NS_ERROR_FAILURE;
@@ -240,4 +232,18 @@ FFmpegDataDecoder<LIBAV_VER>::PrepareFrame()
   return mFrame;
 }
 
+/* static */ AVCodec*
+FFmpegDataDecoder<LIBAV_VER>::FindAVCodec(AVCodecID aCodec)
+{
+  StaticMutexAutoLock mon(sMonitor);
+  if (!sFFmpegInitDone) {
+    avcodec_register_all();
+#ifdef DEBUG
+    av_log_set_level(AV_LOG_DEBUG);
+#endif
+    sFFmpegInitDone = true;
+  }
+  return avcodec_find_decoder(aCodec);
+}
+  
 } // namespace mozilla

dom/media/platforms/ffmpeg/FFmpegDataDecoder.h

@@ -36,6 +36,8 @@ public:
   nsresult Drain() override;
   nsresult Shutdown() override;
 
+  static AVCodec* FindAVCodec(AVCodecID aCodec);
+
 protected:
   // Flush and Drain operation, always run
   virtual void ProcessFlush();

dom/media/platforms/ffmpeg/FFmpegDecoderModule.h

@@ -68,8 +68,13 @@ public:
 
   bool SupportsMimeType(const nsACString& aMimeType) override
   {
-    return FFmpegAudioDecoder<V>::GetCodecId(aMimeType) != AV_CODEC_ID_NONE ||
-      FFmpegH264Decoder<V>::GetCodecId(aMimeType) != AV_CODEC_ID_NONE;
+    AVCodecID audioCodec = FFmpegAudioDecoder<V>::GetCodecId(aMimeType);
+    AVCodecID videoCodec = FFmpegH264Decoder<V>::GetCodecId(aMimeType);
+    if (audioCodec == AV_CODEC_ID_NONE && videoCodec == AV_CODEC_ID_NONE) {
+      return false;
+    }
+    AVCodecID codec = audioCodec != AV_CODEC_ID_NONE ? audioCodec : videoCodec;
+    return !!FFmpegDataDecoder<V>::FindAVCodec(codec);
   }
 
   ConversionRequired