Add reference frame invalidation for the software decoder

app/streaming/video/ffmpeg.h

@@ -20,6 +20,7 @@ public:
                             int maxFps,
                             bool enableVsync) override;
     virtual bool isHardwareAccelerated() override;
+    virtual int getDecoderCapabilities() override;
     virtual int submitDecodeUnit(PDECODE_UNIT du) override;
     virtual void renderFrame(SDL_UserEvent* event) override;
     virtual void dropFrame(SDL_UserEvent* event) override;