Allow FFmpeg renderers to enforce V-sync being enabled or disabled

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

@@ -624,6 +624,11 @@ int DXVA2Renderer::getDecoderCapabilities()
     return 0;
 }
 
+IFFmpegRenderer::VSyncConstraint DXVA2Renderer::getVsyncConstraint()
+{
+    return VSYNC_ANY;
+}
+
 void DXVA2Renderer::renderFrameAtVsync(AVFrame *frame)
 {
     IDirect3DSurface9* surface = reinterpret_cast<IDirect3DSurface9*>(frame->data[3]);

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

@@ -25,6 +25,7 @@ public:
     virtual void renderFrameAtVsync(AVFrame* frame);
     virtual bool needsTestFrame();
     virtual int getDecoderCapabilities();
+    virtual VSyncConstraint getVsyncConstraint();
 
 private:
     bool initializeDecoder();

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

@@ -8,6 +8,12 @@ extern "C" {
 
 class IFFmpegRenderer {
 public:
+    enum VSyncConstraint {
+        VSYNC_FORCE_OFF,
+        VSYNC_FORCE_ON,
+        VSYNC_ANY
+    };
+
     virtual ~IFFmpegRenderer() {}
     virtual bool initialize(SDL_Window* window,
                             int videoFormat,
@@ -19,6 +25,7 @@ public:
     virtual void renderFrameAtVsync(AVFrame* frame) = 0;
     virtual bool needsTestFrame() = 0;
     virtual int getDecoderCapabilities() = 0;
+    virtual VSyncConstraint getVsyncConstraint() = 0;
 };
 
 class SdlRenderer : public IFFmpegRenderer {
@@ -35,6 +42,7 @@ public:
     virtual void renderFrameAtVsync(AVFrame* frame);
     virtual bool needsTestFrame();
     virtual int getDecoderCapabilities();
+    virtual VSyncConstraint getVsyncConstraint();
 
 private:
     SDL_Renderer* m_Renderer;

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

@@ -43,6 +43,11 @@ int SdlRenderer::getDecoderCapabilities()
     return CAPABILITY_REFERENCE_FRAME_INVALIDATION_AVC;
 }
 
+IFFmpegRenderer::VSyncConstraint SdlRenderer::getVsyncConstraint()
+{
+    return VSYNC_ANY;
+}
+
 bool SdlRenderer::initialize(SDL_Window* window,
                              int,
                              int width,

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

@@ -155,6 +155,11 @@ VAAPIRenderer::getDecoderCapabilities()
     return 0;
 }
 
+IFFmpegRenderer::VSyncConstraint VAAPIRenderer::getVsyncConstraint()
+{
+    return VSYNC_ANY;
+}
+
 void
 VAAPIRenderer::renderFrameAtVsync(AVFrame* frame)
 {

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

@@ -40,6 +40,7 @@ public:
     virtual void renderFrameAtVsync(AVFrame* frame);
     virtual bool needsTestFrame();
     virtual int getDecoderCapabilities();
+    virtual VSyncConstraint getVsyncConstraint();
 
 private:
     int m_WindowSystem;

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

@@ -238,6 +238,11 @@ int VDPAURenderer::getDecoderCapabilities()
     return 0;
 }
 
+IFFmpegRenderer::VSyncConstraint VDPAURenderer::getVsyncConstraint()
+{
+    return VSYNC_ANY;
+}
+
 void VDPAURenderer::renderFrameAtVsync(AVFrame* frame)
 {
     VdpStatus status;

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

@@ -23,6 +23,7 @@ public:
     virtual void renderFrameAtVsync(AVFrame* frame);
     virtual bool needsTestFrame();
     virtual int getDecoderCapabilities();
+    virtual VSyncConstraint getVsyncConstraint();
 
 private:
     uint32_t m_VideoWidth, m_VideoHeight;

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

@@ -201,6 +201,14 @@ public:
         return 0;
     }
 
+    virtual IFFmpegRenderer::VSyncConstraint getVsyncConstraint() override
+    {
+        // This renderer is inherently tied to V-sync due how we're
+        // rendering with AVSampleBufferDisplay layer. Running without
+        // the V-Sync source leads to massive stuttering.
+        return VSYNC_FORCE_ON;
+    }
+
 private:
     void setupDisplayLayer()
     {

app/streaming/video/ffmpeg.cpp

@@ -120,6 +120,18 @@ bool FFmpegVideoDecoder::completeInitialization(AVCodec* decoder, SDL_Window* wi
                                                 int videoFormat, int width, int height,
                                                 int maxFps, bool enableVsync, bool testOnly)
 {
+    auto vsyncConstraint = m_Renderer->getVsyncConstraint();
+    if (vsyncConstraint == IFFmpegRenderer::VSYNC_FORCE_OFF && enableVsync) {
+        SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
+                    "V-sync is forcefully disabled by the active renderer");
+        enableVsync = false;
+    }
+    else if (vsyncConstraint == IFFmpegRenderer::VSYNC_FORCE_ON && !enableVsync) {
+        SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
+                    "V-sync is forcefully enabled by the active renderer");
+        enableVsync = true;
+    }
+
     m_Pacer = new Pacer(m_Renderer);
     if (!m_Pacer->initialize(window, maxFps, enableVsync)) {
         return false;