From 8b50eea485aa09a342c2c73a5b12549539f946a1 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Fri, 30 Aug 2024 22:22:30 -0500
Subject: [PATCH] Wait on a dummy fence before using textures shared with the
 decoder

---
 .../video/ffmpeg-renderers/d3d11va.cpp        | 57 +++++++++++++++++++
 .../video/ffmpeg-renderers/d3d11va.h          | 12 +++-
 2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/app/streaming/video/ffmpeg-renderers/d3d11va.cpp b/app/streaming/video/ffmpeg-renderers/d3d11va.cpp
index d5f90f6d..fc5cd112 100644
--- a/app/streaming/video/ffmpeg-renderers/d3d11va.cpp
+++ b/app/streaming/video/ffmpeg-renderers/d3d11va.cpp
@@ -109,6 +109,8 @@ D3D11VARenderer::~D3D11VARenderer()
 
     SDL_DestroyMutex(m_ContextLock);
 
+    m_DecodeFence.Reset();
+
     m_VideoVertexBuffer.Reset();
     for (auto& shader : m_VideoPixelShaders) {
         shader.Reset();
@@ -244,6 +246,26 @@ bool D3D11VARenderer::createDeviceByAdapterIndex(int adapterIndex, bool* adapter
         m_DevicesWithFL11Support++;
     }
 
+    // Check which fence types are supported by this GPU
+    {
+        m_FenceType = SupportedFenceType::None;
+
+        ComPtr<IDXGIAdapter4> adapter4;
+        if (SUCCEEDED(adapter.As(&adapter4))) {
+            DXGI_ADAPTER_DESC3 desc3;
+            if (SUCCEEDED(adapter4->GetDesc3(&desc3))) {
+                if (desc3.Flags & DXGI_ADAPTER_FLAG3_SUPPORT_MONITORED_FENCES) {
+                    // Monitored fences must be used when they are supported
+                    m_FenceType = SupportedFenceType::Monitored;
+                }
+                else if (desc3.Flags & DXGI_ADAPTER_FLAG3_SUPPORT_NON_MONITORED_FENCES) {
+                    // Non-monitored fences must only be used when monitored fences are unsupported
+                    m_FenceType = SupportedFenceType::NonMonitored;
+                }
+            }
+        }
+    }
+
     if (!checkDecoderSupport(adapter.Get())) {
         m_DeviceContext.Reset();
         m_Device.Reset();
@@ -565,6 +587,20 @@ void D3D11VARenderer::renderFrame(AVFrame* frame)
     // access from inside FFmpeg's decoding code
     lockContext(this);
 
+    // Ensure decoding operations have completed using a dummy fence.
+    // This is not necessary on modern GPU drivers, but it is required
+    // on some older GPU drivers that don't properly synchronize the
+    // video engine with 3D operations.
+    if (m_BindDecoderOutputTextures && m_DecodeFence) {
+        ComPtr<ID3D11DeviceContext4> deviceContext4;
+        if (SUCCEEDED(m_DeviceContext.As(&deviceContext4))) {
+            auto desiredFenceValue = m_DecodeFence->GetCompletedValue() + 1;
+            if (SUCCEEDED(deviceContext4->Signal(m_DecodeFence.Get(), desiredFenceValue))) {
+                deviceContext4->Wait(m_DecodeFence.Get(), desiredFenceValue);
+            }
+        }
+    }
+
     // Clear the back buffer
     const float clearColor[4] = {0.0f, 0.0f, 0.0f, 0.0f};
     m_DeviceContext->ClearRenderTargetView(m_RenderTargetView.Get(), clearColor);
@@ -1457,6 +1493,27 @@ bool D3D11VARenderer::setupRenderingResources()
         m_DeviceContext->RSSetViewports(1, &viewport);
     }
 
+    // Create our decoding fence if the GPU supports fences
+    if (m_FenceType != SupportedFenceType::None) {
+        ComPtr<ID3D11Device5> device5;
+        if (SUCCEEDED(m_Device.As(&device5))) {
+            hr = device5->CreateFence(0,
+                                      m_FenceType == SupportedFenceType::Monitored ?
+                                          D3D11_FENCE_FLAG_NONE : D3D11_FENCE_FLAG_NON_MONITORED,
+                                      IID_PPV_ARGS(&m_DecodeFence));
+            if (FAILED(hr)) {
+                // Non-fatal
+                SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
+                            "ID3D11Device5::CreateFence() failed: %x",
+                            hr);
+            }
+        }
+        else {
+            SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
+                        "ID3D11Device5::CreateFence() not available until Windows 10 1703");
+        }
+    }
+
     return true;
 }
 
diff --git a/app/streaming/video/ffmpeg-renderers/d3d11va.h b/app/streaming/video/ffmpeg-renderers/d3d11va.h
index ea6c8334..5712f1a6 100644
--- a/app/streaming/video/ffmpeg-renderers/d3d11va.h
+++ b/app/streaming/video/ffmpeg-renderers/d3d11va.h
@@ -2,8 +2,8 @@
 
 #include "renderer.h"
 
-#include <d3d11_1.h>
-#include <dxgi1_5.h>
+#include <d3d11_4.h>
+#include <dxgi1_6.h>
 
 extern "C" {
 #include <libavutil/hwcontext_d3d11va.h>
@@ -53,11 +53,19 @@ private:
     int m_DevicesWithFL11Support;
     int m_DevicesWithCodecSupport;
 
+    enum class SupportedFenceType {
+        None,
+        NonMonitored,
+        Monitored,
+    };
+
     Microsoft::WRL::ComPtr<IDXGIFactory5> m_Factory;
     Microsoft::WRL::ComPtr<ID3D11Device> m_Device;
     Microsoft::WRL::ComPtr<IDXGISwapChain4> m_SwapChain;
     Microsoft::WRL::ComPtr<ID3D11DeviceContext> m_DeviceContext;
     Microsoft::WRL::ComPtr<ID3D11RenderTargetView> m_RenderTargetView;
+    Microsoft::WRL::ComPtr<ID3D11Fence> m_DecodeFence;
+    SupportedFenceType m_FenceType;
     SDL_mutex* m_ContextLock;
     bool m_BindDecoderOutputTextures;