Avoid the test frame for DXVA2 and VT APIs to address flickering in full-screen on Win7

app/streaming/video/ffmpeg-renderers/dxva2.cpp

@@ -496,6 +496,13 @@ bool DXVA2Renderer::initialize(SDL_Window* window, int videoFormat, int width, i
     return true;
 }
 
+bool DXVA2Renderer::needsTestFrame()
+{
+    // We validate the DXVA2 profiles are supported
+    // in initialize() so no test frame is required
+    return false;
+}
+
 void DXVA2Renderer::renderFrameAtVsync(AVFrame *frame)
 {
     IDirect3DSurface9* surface = reinterpret_cast<IDirect3DSurface9*>(frame->data[3]);

app/streaming/video/ffmpeg-renderers/dxva2.h

@@ -22,6 +22,7 @@ public:
                             int maxFps);
     virtual bool prepareDecoderContext(AVCodecContext* context);
     virtual void renderFrameAtVsync(AVFrame* frame);
+    virtual bool needsTestFrame();
 
 private:
     bool initializeDecoder();

app/streaming/video/ffmpeg-renderers/renderer.h

@@ -16,6 +16,7 @@ public:
                             int maxFps) = 0;
     virtual bool prepareDecoderContext(AVCodecContext* context) = 0;
     virtual void renderFrameAtVsync(AVFrame* frame) = 0;
+    virtual bool needsTestFrame() = 0;
 };
 
 class SdlRenderer : public IFFmpegRenderer {
@@ -29,6 +30,7 @@ public:
                             int maxFps);
     virtual bool prepareDecoderContext(AVCodecContext* context);
     virtual void renderFrameAtVsync(AVFrame* frame);
+    virtual bool needsTestFrame();
 
 private:
     SDL_Renderer* m_Renderer;

app/streaming/video/ffmpeg-renderers/sdl.cpp

@@ -30,6 +30,12 @@ bool SdlRenderer::prepareDecoderContext(AVCodecContext*)
     return true;
 }
 
+bool SdlRenderer::needsTestFrame()
+{
+    // This renderer should always work
+    return false;
+}
+
 bool SdlRenderer::initialize(SDL_Window* window,
                              int,
                              int width,

app/streaming/video/ffmpeg-renderers/vaapi.cpp

@@ -141,6 +141,14 @@ VAAPIRenderer::prepareDecoderContext(AVCodecContext* context)
     return true;
 }
 
+bool
+VAAPIRenderer::needsTestFrame()
+{
+    // We need a test frame to see if this VAAPI driver
+    // supports the profile used for streaming
+    return true;
+}
+
 void
 VAAPIRenderer::renderFrameAtVsync(AVFrame* frame)
 {

app/streaming/video/ffmpeg-renderers/vaapi.h

@@ -37,6 +37,7 @@ public:
                             int maxFps);
     virtual bool prepareDecoderContext(AVCodecContext* context);
     virtual void renderFrameAtVsync(AVFrame* frame);
+    virtual bool needsTestFrame();
 
 private:
     int m_WindowSystem;

app/streaming/video/ffmpeg-renderers/vdpau.cpp

@@ -223,6 +223,13 @@ bool VDPAURenderer::prepareDecoderContext(AVCodecContext* context)
     return true;
 }
 
+bool VDPAURenderer::needsTestFrame()
+{
+    // We need a test frame to see if this VDPAU driver
+    // supports the profile used for streaming
+    return true;
+}
+
 void VDPAURenderer::renderFrameAtVsync(AVFrame* frame)
 {
     VdpStatus status;

app/streaming/video/ffmpeg-renderers/vdpau.h

@@ -20,6 +20,7 @@ public:
                             int maxFps);
     virtual bool prepareDecoderContext(AVCodecContext* context);
     virtual void renderFrameAtVsync(AVFrame* frame);
+    virtual bool needsTestFrame();
 
 private:
     uint32_t m_VideoWidth, m_VideoHeight;

app/streaming/video/ffmpeg-renderers/vt.mm

@@ -189,6 +189,12 @@ public:
         return true;
     }
 
+    virtual bool needsTestFrame() override
+    {
+        // We query VT to determine whether the codec is supported
+        return false;
+    }
+
 private:
     void setupDisplayLayer()
     {