From 9aa487418f0e5668fd18cdec6d2220004644aee3 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Mon, 3 Sep 2018 23:34:15 -0700
Subject: [PATCH] Force V-Sync enabled for DXVA2 windowed with DWM composition
 enabled

---
 app/streaming/video/ffmpeg-renderers/dxva2.cpp | 7 ++++++-
 app/streaming/video/ffmpeg-renderers/dxva2.h   | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/app/streaming/video/ffmpeg-renderers/dxva2.cpp b/app/streaming/video/ffmpeg-renderers/dxva2.cpp
index 23590faf..95d9566e 100644
--- a/app/streaming/video/ffmpeg-renderers/dxva2.cpp
+++ b/app/streaming/video/ffmpeg-renderers/dxva2.cpp
@@ -17,6 +17,7 @@ DEFINE_GUID(DXVADDI_Intel_ModeH264_E, 0x604F8E68,0x4951,0x4C54,0x88,0xFE,0xAB,0x
 #define SAFE_COM_RELEASE(x) if (x) { (x)->Release(); }
 
 DXVA2Renderer::DXVA2Renderer() :
+    m_ForceVsyncOn(false),
     m_DecService(nullptr),
     m_Decoder(nullptr),
     m_SurfacesUsed(0),
@@ -494,6 +495,10 @@ bool DXVA2Renderer::initializeDevice(SDL_Window* window, bool enableVsync)
         d3dpp.SwapEffect = D3DSWAPEFFECT_FLIPEX;
         d3dpp.BackBufferCount = 2;
 
+        // We need our V-sync source enabled to synchronize with DWM composition
+        // and avoid micro-stuttering.
+        m_ForceVsyncOn = true;
+
         SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
                     "Windowed mode with DWM running");
     }
@@ -626,7 +631,7 @@ int DXVA2Renderer::getDecoderCapabilities()
 
 IFFmpegRenderer::VSyncConstraint DXVA2Renderer::getVsyncConstraint()
 {
-    return VSYNC_ANY;
+    return m_ForceVsyncOn ? VSYNC_FORCE_ON : VSYNC_ANY;
 }
 
 void DXVA2Renderer::renderFrameAtVsync(AVFrame *frame)
diff --git a/app/streaming/video/ffmpeg-renderers/dxva2.h b/app/streaming/video/ffmpeg-renderers/dxva2.h
index 5b0ae473..068e49b9 100644
--- a/app/streaming/video/ffmpeg-renderers/dxva2.h
+++ b/app/streaming/video/ffmpeg-renderers/dxva2.h
@@ -45,6 +45,7 @@ private:
     int m_VideoFormat;
     int m_VideoWidth;
     int m_VideoHeight;
+    bool m_ForceVsyncOn;
 
     int m_DisplayWidth;
     int m_DisplayHeight;