Separate FFmpeg decoder from the Session class (#4)

app/streaming/video/decoder.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <Limelight.h>
+#include <SDL.h>
+#include "settings/streamingpreferences.h"
+
+#define SDL_CODE_FRAME_READY 0
+
+#define MAX_SLICES 4
+
+class IVideoDecoder {
+public:
+    virtual ~IVideoDecoder() {}
+    virtual bool initialize(StreamingPreferences::VideoDecoderSelection vds,
+                            SDL_Window* window,
+                            int videoFormat,
+                            int width,
+                            int height,
+                            int frameRate) = 0;
+    virtual bool isHardwareAccelerated() = 0;
+    virtual int submitDecodeUnit(PDECODE_UNIT du) = 0;
+    virtual void renderFrame(SDL_UserEvent* event) = 0;
+    virtual void dropFrame(SDL_UserEvent* event) = 0;
+
+    virtual void queueFrame(void* data1 = nullptr,
+                            void* data2 = nullptr)
+    {
+        SDL_Event event;
+
+        event.type = SDL_USEREVENT;
+        event.user.code = SDL_CODE_FRAME_READY;
+        event.user.data1 = data1;
+        event.user.data2 = data2;
+
+        SDL_PushEvent(&event);
+    }
+};