Validate that the codec is functional before using it. Fixes streaming failure with VAAPI if hardware lacks codec support

app/streaming/video/ffmpeg.h

@@ -23,15 +23,13 @@ public:
     virtual void dropFrame(SDL_UserEvent* event) override;
 
 private:
-    bool
-    chooseDecoder(
-        StreamingPreferences::VideoDecoderSelection vds,
-        SDL_Window* window,
-        int videoFormat,
-        int width, int height,
-        AVCodec*& chosenDecoder,
-        const AVCodecHWConfig*& chosenHwConfig,
-        IFFmpegRenderer*& newRenderer);
+    bool completeInitialization(AVCodec* decoder, int videoFormat, int width, int height, bool testOnly);
+
+    void reset();
+
+    static
+    enum AVPixelFormat ffGetFormat(AVCodecContext* context,
+                                   const enum AVPixelFormat* pixFmts);
 
     AVPacket m_Pkt;
     AVCodecContext* m_VideoDecoderCtx;
@@ -39,4 +37,7 @@ private:
     const AVCodecHWConfig* m_HwDecodeCfg;
     IFFmpegRenderer* m_Renderer;
     SDL_atomic_t m_QueuedFrames;
+
+    static const uint8_t k_H264TestFrame[];
+    static const uint8_t k_HEVCTestFrame[];
 };