ore untangling

2026-05-10 23:31:45 +10:00
parent 739231d5a1
commit 7f0f60c0e3
11 changed files with 593 additions and 176 deletions
--- a/apps/LoopThroughWithOpenGLCompositing/gl/OpenGLComposite.cpp
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/OpenGLComposite.cpp
@@ -1,16 +1,13 @@
 #include "DeckLinkDisplayMode.h"
-#include "DeckLinkSession.h"
 #include "OpenGLComposite.h"
 #include "GLExtensions.h"
 #include "GlRenderConstants.h"
-#include "OpenGLRenderPass.h"
-#include "OpenGLRenderPipeline.h"
-#include "OpenGLShaderPrograms.h"
-#include "OpenGLVideoIOBridge.h"
 #include "PngScreenshotWriter.h"
+#include "RenderEngine.h"
 #include "RuntimeParameterUtils.h"
 #include "RuntimeServices.h"
 #include "ShaderBuildQueue.h"
+#include "VideoBackend.h"

 #include <algorithm>
 #include <cctype>
@@ -97,8 +94,6 @@ JsonValue BuildOscCommitValue(const ShaderParameterDefinition& definition, const

 OpenGLComposite::OpenGLComposite(HWND hWnd, HDC hDC, HGLRC hRC) :
 	hGLWnd(hWnd), hGLDC(hDC), hGLRC(hRC),
-	mVideoIO(std::make_unique<DeckLinkSession>()),
-	mRenderer(std::make_unique<OpenGLRenderer>()),
 	mUseCommittedLayerStates(false),
 	mScreenshotRequested(false)
 {
@@ -106,22 +101,16 @@ OpenGLComposite::OpenGLComposite(HWND hWnd, HDC hDC, HGLRC hRC) :
 	mRuntimeHost = std::make_unique<RuntimeHost>();
 	mRuntimeStore = std::make_unique<RuntimeStore>(*mRuntimeHost);
 	mRuntimeSnapshotProvider = std::make_unique<RuntimeSnapshotProvider>(*mRuntimeHost);
-	mRenderPipeline = std::make_unique<OpenGLRenderPipeline>(
-		*mRenderer,
+	mRenderEngine = std::make_unique<RenderEngine>(
 		*mRuntimeHost,
+		*mRuntimeSnapshotProvider,
+		pMutex,
+		hGLDC,
+		hGLRC,
 		[this]() { renderEffect(); },
 		[this]() { ProcessScreenshotRequest(); },
 		[this]() { paintGL(false); });
-	mVideoIOBridge = std::make_unique<OpenGLVideoIOBridge>(
-		*mVideoIO,
-		*mRenderer,
-		*mRenderPipeline,
-		*mRuntimeHost,
-		pMutex,
-		hGLDC,
-		hGLRC);
-	mRenderPass = std::make_unique<OpenGLRenderPass>(*mRenderer);
-	mShaderPrograms = std::make_unique<OpenGLShaderPrograms>(*mRenderer, *mRuntimeHost, *mRuntimeSnapshotProvider);
+	mVideoBackend = std::make_unique<VideoBackend>(*mRenderEngine, mRuntimeHost->GetHealthTelemetry());
 	mShaderBuildQueue = std::make_unique<ShaderBuildQueue>(*mRuntimeSnapshotProvider);
 	mRuntimeServices = std::make_unique<RuntimeServices>();
 }
@@ -132,8 +121,8 @@ OpenGLComposite::~OpenGLComposite()
 		mRuntimeServices->Stop();
 	if (mShaderBuildQueue)
 		mShaderBuildQueue->Stop();
-	mVideoIO->ReleaseResources();
-	mRenderer->DestroyResources();
+	if (mVideoBackend)
+		mVideoBackend->ReleaseResources();

 	DeleteCriticalSection(&pMutex);
 }
@@ -173,7 +162,7 @@ bool OpenGLComposite::InitVideoIO()
 		}
 	}

-	if (!mVideoIO->DiscoverDevicesAndModes(videoModes, initFailureReason))
+	if (!mVideoBackend->DiscoverDevicesAndModes(videoModes, initFailureReason))
 	{
 		const char* title = initFailureReason == "Please install the Blackmagic DeckLink drivers to use the features of this application."
 			? "This application requires the DeckLink drivers installed."
@@ -182,7 +171,7 @@ bool OpenGLComposite::InitVideoIO()
 		return false;
 	}
 	const bool outputAlphaRequired = mRuntimeStore && mRuntimeStore->IsExternalKeyingConfigured();
-	if (!mVideoIO->SelectPreferredFormats(videoModes, outputAlphaRequired, initFailureReason))
+	if (!mVideoBackend->SelectPreferredFormats(videoModes, outputAlphaRequired, initFailureReason))
 		goto error;

 	if (! CheckOpenGLExtensions())
@@ -197,38 +186,38 @@ bool OpenGLComposite::InitVideoIO()
 		goto error;
 	}

-	PublishVideoIOStatus(mVideoIO->OutputModelName().empty()
+	PublishVideoIOStatus(mVideoBackend->OutputModelName().empty()
 		? "DeckLink output device selected."
-		: ("Selected output device: " + mVideoIO->OutputModelName()));
+		: ("Selected output device: " + mVideoBackend->OutputModelName()));

 	// Resize window to match output video frame, but scale large formats down by half for viewing.
-	if (mVideoIO->OutputFrameWidth() < 1920)
-		resizeWindow(mVideoIO->OutputFrameWidth(), mVideoIO->OutputFrameHeight());
+	if (mVideoBackend->OutputFrameWidth() < 1920)
+		resizeWindow(mVideoBackend->OutputFrameWidth(), mVideoBackend->OutputFrameHeight());
 	else
-		resizeWindow(mVideoIO->OutputFrameWidth() / 2, mVideoIO->OutputFrameHeight() / 2);
+		resizeWindow(mVideoBackend->OutputFrameWidth() / 2, mVideoBackend->OutputFrameHeight() / 2);

-	if (!mVideoIO->ConfigureInput([this](const VideoIOFrame& frame) { mVideoIOBridge->VideoFrameArrived(frame); }, videoModes.input, initFailureReason))
+	if (!mVideoBackend->ConfigureInput(videoModes.input, initFailureReason))
 	{
 		goto error;
 	}
-	if (!mVideoIO->HasInputDevice() && mRuntimeHost)
+	if (!mVideoBackend->HasInputDevice() && mRuntimeHost)
 	{
-		mRuntimeHost->SetSignalStatus(false, mVideoIO->InputFrameWidth(), mVideoIO->InputFrameHeight(), mVideoIO->InputDisplayModeName());
+		mRuntimeHost->SetSignalStatus(false, mVideoBackend->InputFrameWidth(), mVideoBackend->InputFrameHeight(), mVideoBackend->InputDisplayModeName());
 	}

-	if (!mVideoIO->ConfigureOutput([this](const VideoIOCompletion& completion) { mVideoIOBridge->PlayoutFrameCompleted(completion); }, videoModes.output, mRuntimeStore && mRuntimeStore->IsExternalKeyingConfigured(), initFailureReason))
+	if (!mVideoBackend->ConfigureOutput(videoModes.output, mRuntimeStore && mRuntimeStore->IsExternalKeyingConfigured(), initFailureReason))
 	{
 		goto error;
 	}

-	PublishVideoIOStatus(mVideoIO->StatusMessage());
+	PublishVideoIOStatus(mVideoBackend->StatusMessage());

 	return true;

 error:
 	if (!initFailureReason.empty())
 		MessageBoxA(NULL, initFailureReason.c_str(), "DeckLink initialization failed", MB_OK | MB_ICONERROR);
-	mVideoIO->ReleaseResources();
+	mVideoBackend->ReleaseResources();
 	return false;
 }

@@ -252,23 +241,21 @@ void OpenGLComposite::paintGL(bool force)
 		}
 	}

-	if (!TryEnterCriticalSection(&pMutex))
+	if (!mRenderEngine->TryPresentToWindow(mVideoBackend->OutputFrameWidth(), mVideoBackend->OutputFrameHeight()))
 	{
 		ValidateRect(hGLWnd, NULL);
 		return;
 	}

-	mRenderer->PresentToWindow(hGLDC, mVideoIO->OutputFrameWidth(), mVideoIO->OutputFrameHeight());
 	mLastPreviewPresentTime = std::chrono::steady_clock::now();
 	ValidateRect(hGLWnd, NULL);
-	LeaveCriticalSection(&pMutex);
 }

 void OpenGLComposite::resizeGL(WORD width, WORD height)
 {
 	// We don't set the project or model matrices here since the window data is copied directly from
 	// an off-screen FBO in paintGL().  Just save the width and height for use in paintGL().
-	mRenderer->ResizeView(width, height);
+	mRenderEngine->ResizeView(width, height);
 }

 void OpenGLComposite::resizeWindow(int width, int height)
@@ -286,17 +273,17 @@ void OpenGLComposite::PublishVideoIOStatus(const std::string& statusMessage)
 		return;

 	if (!statusMessage.empty())
-		mVideoIO->SetStatusMessage(statusMessage);
+		mVideoBackend->SetStatusMessage(statusMessage);

 	mRuntimeHost->SetVideoIOStatus(
 		"decklink",
-		mVideoIO->OutputModelName(),
-		mVideoIO->SupportsInternalKeying(),
-		mVideoIO->SupportsExternalKeying(),
-		mVideoIO->KeyerInterfaceAvailable(),
+		mVideoBackend->OutputModelName(),
+		mVideoBackend->SupportsInternalKeying(),
+		mVideoBackend->SupportsExternalKeying(),
+		mVideoBackend->KeyerInterfaceAvailable(),
 		mRuntimeStore ? mRuntimeStore->IsExternalKeyingConfigured() : false,
-		mVideoIO->ExternalKeyingActive(),
-		mVideoIO->StatusMessage());
+		mVideoBackend->ExternalKeyingActive(),
+		mVideoBackend->StatusMessage());
 }

 bool OpenGLComposite::InitOpenGLState()
@@ -319,41 +306,41 @@ bool OpenGLComposite::InitOpenGLState()

 	// Prepare the runtime shader program generated from the active shader package.
 	char compilerErrorMessage[1024];
-	if (!mShaderPrograms->CompileDecodeShader(sizeof(compilerErrorMessage), compilerErrorMessage))
+	if (!mRenderEngine->CompileDecodeShader(sizeof(compilerErrorMessage), compilerErrorMessage))
 	{
 		MessageBoxA(NULL, compilerErrorMessage, "OpenGL decode shader failed to load or compile", MB_OK);
 		return false;
 	}
-	if (!mShaderPrograms->CompileOutputPackShader(sizeof(compilerErrorMessage), compilerErrorMessage))
+	if (!mRenderEngine->CompileOutputPackShader(sizeof(compilerErrorMessage), compilerErrorMessage))
 	{
 		MessageBoxA(NULL, compilerErrorMessage, "OpenGL output pack shader failed to load or compile", MB_OK);
 		return false;
 	}

 	std::string rendererError;
-	if (!mRenderer->InitializeResources(
-		mVideoIO->InputFrameWidth(),
-		mVideoIO->InputFrameHeight(),
-		mVideoIO->CaptureTextureWidth(),
-		mVideoIO->OutputFrameWidth(),
-		mVideoIO->OutputFrameHeight(),
-		mVideoIO->OutputPackTextureWidth(),
+	if (!mRenderEngine->InitializeResources(
+		mVideoBackend->InputFrameWidth(),
+		mVideoBackend->InputFrameHeight(),
+		mVideoBackend->CaptureTextureWidth(),
+		mVideoBackend->OutputFrameWidth(),
+		mVideoBackend->OutputFrameHeight(),
+		mVideoBackend->OutputPackTextureWidth(),
 		rendererError))
 	{
 		MessageBoxA(NULL, rendererError.c_str(), "OpenGL initialization error.", MB_OK);
 		return false;
 	}

-	if (!mShaderPrograms->CompileLayerPrograms(mVideoIO->InputFrameWidth(), mVideoIO->InputFrameHeight(), sizeof(compilerErrorMessage), compilerErrorMessage))
+	if (!mRenderEngine->CompileLayerPrograms(mVideoBackend->InputFrameWidth(), mVideoBackend->InputFrameHeight(), sizeof(compilerErrorMessage), compilerErrorMessage))
 	{
 		MessageBoxA(NULL, compilerErrorMessage, "OpenGL shader failed to load or compile", MB_OK);
 		return false;
 	}
-	mCachedLayerRenderStates = mShaderPrograms->CommittedLayerStates();
+	mCachedLayerRenderStates = mRenderEngine->CommittedLayerStates();
 	mUseCommittedLayerStates = false;

-	mShaderPrograms->ResetTemporalHistoryState();
-	mShaderPrograms->ResetShaderFeedbackState();
+	mRenderEngine->ResetTemporalHistoryState();
+	mRenderEngine->ResetShaderFeedbackState();

 	broadcastRuntimeState();
 	mRuntimeServices->BeginPolling(*mRuntimeHost);
@@ -362,7 +349,7 @@ bool OpenGLComposite::InitOpenGLState()

 bool OpenGLComposite::Start()
 {
-	return mVideoIO->Start();
+	return mVideoBackend->Start();
 }

 bool OpenGLComposite::Stop()
@@ -370,8 +357,8 @@ bool OpenGLComposite::Stop()
 	if (mRuntimeServices)
 		mRuntimeServices->Stop();

-	const bool wasExternalKeyingActive = mVideoIO->ExternalKeyingActive();
-	mVideoIO->Stop();
+	const bool wasExternalKeyingActive = mVideoBackend->ExternalKeyingActive();
+	mVideoBackend->Stop();
 	if (wasExternalKeyingActive)
 		PublishVideoIOStatus("External keying has been disabled.");

@@ -587,19 +574,19 @@ void OpenGLComposite::renderEffect()
 			mOscOverlayStates.erase(overlayKey);
 	};

-	const bool hasInputSource = mVideoIO->HasInputSource();
+	const bool hasInputSource = mVideoBackend->HasInputSource();
 	std::vector<RuntimeRenderState> layerStates;
 	if (mUseCommittedLayerStates)
 	{
-		layerStates = mShaderPrograms->CommittedLayerStates();
+		layerStates = mRenderEngine->CommittedLayerStates();
 		applyOscOverlays(layerStates, false);
 		if (mRuntimeSnapshotProvider)
 			mRuntimeSnapshotProvider->RefreshDynamicRenderStateFields(layerStates);
 	}
 	else if (mRuntimeSnapshotProvider)
 	{
-		const unsigned renderWidth = mVideoIO->InputFrameWidth();
-		const unsigned renderHeight = mVideoIO->InputFrameHeight();
+		const unsigned renderWidth = mVideoBackend->InputFrameWidth();
+		const unsigned renderHeight = mVideoBackend->InputFrameHeight();
 		const RuntimeSnapshotVersions versions = mRuntimeSnapshotProvider->GetVersions();
 		const bool renderStateCacheValid =
 			!mCachedLayerRenderStates.empty() &&
@@ -650,20 +637,14 @@ void OpenGLComposite::renderEffect()
 		}
 	}
 	const unsigned historyCap = mRuntimeStore ? mRuntimeStore->GetConfiguredMaxTemporalHistoryFrames() : 0;
-	mRenderPass->Render(
+	mRenderEngine->RenderLayerStack(
 		hasInputSource,
 		layerStates,
-		mVideoIO->InputFrameWidth(),
-		mVideoIO->InputFrameHeight(),
-		mVideoIO->CaptureTextureWidth(),
-		mVideoIO->InputPixelFormat(),
-		historyCap,
-		[this](const RuntimeRenderState& state, LayerProgram::TextBinding& textBinding, std::string& error) {
-			return mShaderPrograms->UpdateTextBindingTexture(state, textBinding, error);
-		},
-		[this](const RuntimeRenderState& state, unsigned availableSourceHistoryLength, unsigned availableTemporalHistoryLength, bool feedbackAvailable) {
-			return mShaderPrograms->UpdateGlobalParamsBuffer(state, availableSourceHistoryLength, availableTemporalHistoryLength, feedbackAvailable);
-		});
+		mVideoBackend->InputFrameWidth(),
+		mVideoBackend->InputFrameHeight(),
+		mVideoBackend->CaptureTextureWidth(),
+		mVideoBackend->InputPixelFormat(),
+		historyCap);
 }

 void OpenGLComposite::ProcessScreenshotRequest()
@@ -671,21 +652,16 @@ void OpenGLComposite::ProcessScreenshotRequest()
 	if (!mScreenshotRequested.exchange(false))
 		return;

-	const unsigned width = mVideoIO ? mVideoIO->OutputFrameWidth() : 0;
-	const unsigned height = mVideoIO ? mVideoIO->OutputFrameHeight() : 0;
+	const unsigned width = mVideoBackend ? mVideoBackend->OutputFrameWidth() : 0;
+	const unsigned height = mVideoBackend ? mVideoBackend->OutputFrameHeight() : 0;
 	if (width == 0 || height == 0)
 		return;

-	std::vector<unsigned char> bottomUpPixels(static_cast<std::size_t>(width) * height * 4);
+	std::vector<unsigned char> bottomUpPixels;
+	if (!mRenderEngine->ReadOutputFrameRgba(width, height, bottomUpPixels))
+		return;
 	std::vector<unsigned char> topDownPixels(bottomUpPixels.size());

-	glBindFramebuffer(GL_READ_FRAMEBUFFER, mRenderer->OutputFramebuffer());
-	glReadBuffer(GL_COLOR_ATTACHMENT0);
-	glPixelStorei(GL_PACK_ALIGNMENT, 1);
-	glPixelStorei(GL_PACK_ROW_LENGTH, 0);
-	glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, bottomUpPixels.data());
-	glPixelStorei(GL_PACK_ALIGNMENT, 4);
-
 	const std::size_t rowBytes = static_cast<std::size_t>(width) * 4;
 	for (unsigned y = 0; y < height; ++y)
 	{
@@ -752,7 +728,7 @@ bool OpenGLComposite::ProcessRuntimePollResults()
 			return true;

 		char compilerErrorMessage[1024] = {};
-		if (!mShaderPrograms->CommitPreparedLayerPrograms(readyBuild, mVideoIO->InputFrameWidth(), mVideoIO->InputFrameHeight(), sizeof(compilerErrorMessage), compilerErrorMessage))
+		if (!mRenderEngine->CommitPreparedLayerPrograms(readyBuild, mVideoBackend->InputFrameWidth(), mVideoBackend->InputFrameHeight(), sizeof(compilerErrorMessage), compilerErrorMessage))
 		{
 			mRuntimeStore->SetCompileStatus(false, compilerErrorMessage);
 			mUseCommittedLayerStates = true;
@@ -762,10 +738,10 @@ bool OpenGLComposite::ProcessRuntimePollResults()
 		}

 		mUseCommittedLayerStates = false;
-		mCachedLayerRenderStates = mShaderPrograms->CommittedLayerStates();
-		mShaderPrograms->ResetTemporalHistoryState();
+		mCachedLayerRenderStates = mRenderEngine->CommittedLayerStates();
+		mRenderEngine->ResetTemporalHistoryState();
 		if (!mPreserveFeedbackOnNextShaderBuild)
-			mShaderPrograms->ResetShaderFeedbackState();
+			mRenderEngine->ResetShaderFeedbackState();
 		mPreserveFeedbackOnNextShaderBuild = false;
 		broadcastRuntimeState();
 		return true;
@@ -780,13 +756,13 @@ bool OpenGLComposite::ProcessRuntimePollResults()

 void OpenGLComposite::RequestShaderBuild()
 {
-	if (!mShaderBuildQueue || !mVideoIO)
+	if (!mShaderBuildQueue || !mVideoBackend)
 		return;

 	mUseCommittedLayerStates = true;
 	if (mRuntimeHost)
 		mRuntimeStore->ClearReloadRequest();
-	mShaderBuildQueue->RequestBuild(mVideoIO->InputFrameWidth(), mVideoIO->InputFrameHeight());
+	mShaderBuildQueue->RequestBuild(mVideoBackend->InputFrameWidth(), mVideoBackend->InputFrameHeight());
 }

 void OpenGLComposite::broadcastRuntimeState()
@@ -797,8 +773,8 @@ void OpenGLComposite::broadcastRuntimeState()

 void OpenGLComposite::resetTemporalHistoryState()
 {
-	mShaderPrograms->ResetTemporalHistoryState();
-	mShaderPrograms->ResetShaderFeedbackState();
+	mRenderEngine->ResetTemporalHistoryState();
+	mRenderEngine->ResetShaderFeedbackState();
 }

 bool OpenGLComposite::CheckOpenGLExtensions()
--- a/apps/LoopThroughWithOpenGLCompositing/gl/OpenGLComposite.h
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/OpenGLComposite.h
@@ -12,7 +12,6 @@
 #include <comutil.h>

 #include "GLExtensions.h"
-#include "OpenGLRenderer.h"
 #include "RuntimeHost.h"
 #include "RuntimeSnapshotProvider.h"
 #include "RuntimeStore.h"
@@ -27,13 +26,10 @@
 #include <deque>
 #include <chrono>

-class VideoIODevice;
-class OpenGLVideoIOBridge;
-class OpenGLRenderPass;
-class OpenGLRenderPipeline;
-class OpenGLShaderPrograms;
+class RenderEngine;
 class RuntimeServices;
 class ShaderBuildQueue;
+class VideoBackend;


 class OpenGLComposite
@@ -74,7 +70,6 @@ private:
 	void resizeWindow(int width, int height);
 	bool CheckOpenGLExtensions();
 	void PublishVideoIOStatus(const std::string& statusMessage);
-	using LayerProgram = OpenGLRenderer::LayerProgram;
 	struct OscOverlayState
 	{
 		std::string layerKey;
@@ -94,17 +89,13 @@ private:
 	HGLRC									hGLRC;
 	CRITICAL_SECTION						pMutex;

-	std::unique_ptr<VideoIODevice>			mVideoIO;
-	std::unique_ptr<OpenGLRenderer>			mRenderer;
 	std::unique_ptr<RuntimeHost>				mRuntimeHost;
 	std::unique_ptr<RuntimeStore>			mRuntimeStore;
 	std::unique_ptr<RuntimeSnapshotProvider>	mRuntimeSnapshotProvider;
-	std::unique_ptr<OpenGLVideoIOBridge>		mVideoIOBridge;
-	std::unique_ptr<OpenGLRenderPass>		mRenderPass;
-	std::unique_ptr<OpenGLRenderPipeline>	mRenderPipeline;
-	std::unique_ptr<OpenGLShaderPrograms>	mShaderPrograms;
+	std::unique_ptr<RenderEngine>			mRenderEngine;
 	std::unique_ptr<ShaderBuildQueue>		mShaderBuildQueue;
 	std::unique_ptr<RuntimeServices>		mRuntimeServices;
+	std::unique_ptr<VideoBackend>			mVideoBackend;
 	std::vector<RuntimeRenderState>			mCachedLayerRenderStates;
 	uint64_t								mCachedRenderStateVersion = 0;
 	uint64_t								mCachedParameterStateVersion = 0;
--- a/apps/LoopThroughWithOpenGLCompositing/gl/RenderEngine.cpp
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/RenderEngine.cpp
@@ -0,0 +1,180 @@
+#include "RenderEngine.h"
+
+#include <gl/gl.h>
+
+RenderEngine::RenderEngine(
+	RuntimeHost& runtimeHost,
+	RuntimeSnapshotProvider& runtimeSnapshotProvider,
+	CRITICAL_SECTION& mutex,
+	HDC hdc,
+	HGLRC hglrc,
+	RenderEffectCallback renderEffect,
+	ScreenshotCallback screenshotReady,
+	PreviewPaintCallback previewPaint) :
+	mRenderer(),
+	mRenderPass(mRenderer),
+	mRenderPipeline(mRenderer, runtimeHost, std::move(renderEffect), std::move(screenshotReady), std::move(previewPaint)),
+	mShaderPrograms(mRenderer, runtimeHost, runtimeSnapshotProvider),
+	mMutex(mutex),
+	mHdc(hdc),
+	mHglrc(hglrc)
+{
+}
+
+RenderEngine::~RenderEngine()
+{
+	mRenderer.DestroyResources();
+}
+
+bool RenderEngine::CompileDecodeShader(int errorMessageSize, char* errorMessage)
+{
+	return mShaderPrograms.CompileDecodeShader(errorMessageSize, errorMessage);
+}
+
+bool RenderEngine::CompileOutputPackShader(int errorMessageSize, char* errorMessage)
+{
+	return mShaderPrograms.CompileOutputPackShader(errorMessageSize, errorMessage);
+}
+
+bool RenderEngine::InitializeResources(
+	unsigned inputFrameWidth,
+	unsigned inputFrameHeight,
+	unsigned captureTextureWidth,
+	unsigned outputFrameWidth,
+	unsigned outputFrameHeight,
+	unsigned outputPackTextureWidth,
+	std::string& error)
+{
+	return mRenderer.InitializeResources(
+		inputFrameWidth,
+		inputFrameHeight,
+		captureTextureWidth,
+		outputFrameWidth,
+		outputFrameHeight,
+		outputPackTextureWidth,
+		error);
+}
+
+bool RenderEngine::CompileLayerPrograms(unsigned inputFrameWidth, unsigned inputFrameHeight, int errorMessageSize, char* errorMessage)
+{
+	return mShaderPrograms.CompileLayerPrograms(inputFrameWidth, inputFrameHeight, errorMessageSize, errorMessage);
+}
+
+bool RenderEngine::CommitPreparedLayerPrograms(const PreparedShaderBuild& preparedBuild, unsigned inputFrameWidth, unsigned inputFrameHeight, int errorMessageSize, char* errorMessage)
+{
+	return mShaderPrograms.CommitPreparedLayerPrograms(preparedBuild, inputFrameWidth, inputFrameHeight, errorMessageSize, errorMessage);
+}
+
+const std::vector<RuntimeRenderState>& RenderEngine::CommittedLayerStates() const
+{
+	return mShaderPrograms.CommittedLayerStates();
+}
+
+void RenderEngine::ResetTemporalHistoryState()
+{
+	mShaderPrograms.ResetTemporalHistoryState();
+}
+
+void RenderEngine::ResetShaderFeedbackState()
+{
+	mShaderPrograms.ResetShaderFeedbackState();
+}
+
+void RenderEngine::ResizeView(int width, int height)
+{
+	mRenderer.ResizeView(width, height);
+}
+
+bool RenderEngine::TryPresentToWindow(unsigned outputFrameWidth, unsigned outputFrameHeight)
+{
+	if (!TryEnterCriticalSection(&mMutex))
+		return false;
+
+	mRenderer.PresentToWindow(mHdc, outputFrameWidth, outputFrameHeight);
+	LeaveCriticalSection(&mMutex);
+	return true;
+}
+
+bool RenderEngine::TryUploadInputFrame(const VideoIOFrame& inputFrame, const VideoIOState& videoState)
+{
+	if (inputFrame.hasNoInputSource || inputFrame.bytes == nullptr)
+		return true;
+
+	const long textureSize = inputFrame.rowBytes * static_cast<long>(inputFrame.height);
+	if (!TryEnterCriticalSection(&mMutex))
+		return false;
+
+	wglMakeCurrent(mHdc, mHglrc);
+
+	glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
+	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+	glBindBuffer(GL_PIXEL_UNPACK_BUFFER, mRenderer.TextureUploadBuffer());
+	glBufferData(GL_PIXEL_UNPACK_BUFFER, textureSize, inputFrame.bytes, GL_DYNAMIC_DRAW);
+	glBindTexture(GL_TEXTURE_2D, mRenderer.CaptureTexture());
+	if (inputFrame.pixelFormat == VideoIOPixelFormat::V210)
+		glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, videoState.captureTextureWidth, videoState.inputFrameSize.height, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+	else
+		glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, videoState.captureTextureWidth, videoState.inputFrameSize.height, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, NULL);
+	glBindTexture(GL_TEXTURE_2D, 0);
+	glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
+
+	wglMakeCurrent(NULL, NULL);
+	LeaveCriticalSection(&mMutex);
+	return true;
+}
+
+bool RenderEngine::RenderOutputFrame(const RenderPipelineFrameContext& context, VideoIOOutputFrame& outputFrame)
+{
+	EnterCriticalSection(&mMutex);
+	wglMakeCurrent(mHdc, mHglrc);
+	const bool rendered = mRenderPipeline.RenderFrame(context, outputFrame);
+	wglMakeCurrent(NULL, NULL);
+	LeaveCriticalSection(&mMutex);
+	return rendered;
+}
+
+void RenderEngine::RenderLayerStack(
+	bool hasInputSource,
+	const std::vector<RuntimeRenderState>& layerStates,
+	unsigned inputFrameWidth,
+	unsigned inputFrameHeight,
+	unsigned captureTextureWidth,
+	VideoIOPixelFormat inputPixelFormat,
+	unsigned historyCap)
+{
+	mRenderPass.Render(
+		hasInputSource,
+		layerStates,
+		inputFrameWidth,
+		inputFrameHeight,
+		captureTextureWidth,
+		inputPixelFormat,
+		historyCap,
+		[this](const RuntimeRenderState& state, OpenGLRenderer::LayerProgram::TextBinding& textBinding, std::string& error) {
+			return mShaderPrograms.UpdateTextBindingTexture(state, textBinding, error);
+		},
+		[this](const RuntimeRenderState& state, unsigned availableSourceHistoryLength, unsigned availableTemporalHistoryLength, bool feedbackAvailable) {
+			return mShaderPrograms.UpdateGlobalParamsBuffer(state, availableSourceHistoryLength, availableTemporalHistoryLength, feedbackAvailable);
+		});
+}
+
+bool RenderEngine::ReadOutputFrameRgba(unsigned width, unsigned height, std::vector<unsigned char>& bottomUpPixels)
+{
+	if (width == 0 || height == 0)
+		return false;
+
+	EnterCriticalSection(&mMutex);
+	wglMakeCurrent(mHdc, mHglrc);
+
+	bottomUpPixels.resize(static_cast<std::size_t>(width) * height * 4);
+	glBindFramebuffer(GL_READ_FRAMEBUFFER, mRenderer.OutputFramebuffer());
+	glReadBuffer(GL_COLOR_ATTACHMENT0);
+	glPixelStorei(GL_PACK_ALIGNMENT, 1);
+	glPixelStorei(GL_PACK_ROW_LENGTH, 0);
+	glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, bottomUpPixels.data());
+	glPixelStorei(GL_PACK_ALIGNMENT, 4);
+
+	wglMakeCurrent(NULL, NULL);
+	LeaveCriticalSection(&mMutex);
+	return true;
+}
--- a/apps/LoopThroughWithOpenGLCompositing/gl/RenderEngine.h
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/RenderEngine.h
@@ -0,0 +1,72 @@
+#pragma once
+
+#include "OpenGLRenderPass.h"
+#include "OpenGLRenderPipeline.h"
+#include "OpenGLRenderer.h"
+#include "OpenGLShaderPrograms.h"
+#include "RuntimeHost.h"
+#include "RuntimeSnapshotProvider.h"
+
+#include <windows.h>
+
+#include <functional>
+#include <string>
+#include <vector>
+
+class RenderEngine
+{
+public:
+	using RenderEffectCallback = std::function<void()>;
+	using ScreenshotCallback = std::function<void()>;
+	using PreviewPaintCallback = std::function<void()>;
+
+	RenderEngine(
+		RuntimeHost& runtimeHost,
+		RuntimeSnapshotProvider& runtimeSnapshotProvider,
+		CRITICAL_SECTION& mutex,
+		HDC hdc,
+		HGLRC hglrc,
+		RenderEffectCallback renderEffect,
+		ScreenshotCallback screenshotReady,
+		PreviewPaintCallback previewPaint);
+	~RenderEngine();
+
+	bool CompileDecodeShader(int errorMessageSize, char* errorMessage);
+	bool CompileOutputPackShader(int errorMessageSize, char* errorMessage);
+	bool InitializeResources(
+		unsigned inputFrameWidth,
+		unsigned inputFrameHeight,
+		unsigned captureTextureWidth,
+		unsigned outputFrameWidth,
+		unsigned outputFrameHeight,
+		unsigned outputPackTextureWidth,
+		std::string& error);
+	bool CompileLayerPrograms(unsigned inputFrameWidth, unsigned inputFrameHeight, int errorMessageSize, char* errorMessage);
+	bool CommitPreparedLayerPrograms(const PreparedShaderBuild& preparedBuild, unsigned inputFrameWidth, unsigned inputFrameHeight, int errorMessageSize, char* errorMessage);
+
+	const std::vector<RuntimeRenderState>& CommittedLayerStates() const;
+	void ResetTemporalHistoryState();
+	void ResetShaderFeedbackState();
+	void ResizeView(int width, int height);
+	bool TryPresentToWindow(unsigned outputFrameWidth, unsigned outputFrameHeight);
+	bool TryUploadInputFrame(const VideoIOFrame& inputFrame, const VideoIOState& videoState);
+	bool RenderOutputFrame(const RenderPipelineFrameContext& context, VideoIOOutputFrame& outputFrame);
+	void RenderLayerStack(
+		bool hasInputSource,
+		const std::vector<RuntimeRenderState>& layerStates,
+		unsigned inputFrameWidth,
+		unsigned inputFrameHeight,
+		unsigned captureTextureWidth,
+		VideoIOPixelFormat inputPixelFormat,
+		unsigned historyCap);
+	bool ReadOutputFrameRgba(unsigned width, unsigned height, std::vector<unsigned char>& bottomUpPixels);
+
+private:
+	OpenGLRenderer mRenderer;
+	OpenGLRenderPass mRenderPass;
+	OpenGLRenderPipeline mRenderPipeline;
+	OpenGLShaderPrograms mShaderPrograms;
+	CRITICAL_SECTION& mMutex;
+	HDC mHdc;
+	HGLRC mHglrc;
+};
--- a/apps/LoopThroughWithOpenGLCompositing/gl/pipeline/OpenGLVideoIOBridge.cpp
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/pipeline/OpenGLVideoIOBridge.cpp
@@ -1,26 +1,17 @@
 #include "OpenGLVideoIOBridge.h"

-#include "OpenGLRenderer.h"
-#include "RuntimeHost.h"
+#include "HealthTelemetry.h"
+#include "RenderEngine.h"

 #include <chrono>
-#include <gl/gl.h>

 OpenGLVideoIOBridge::OpenGLVideoIOBridge(
 	VideoIODevice& videoIO,
-	OpenGLRenderer& renderer,
-	OpenGLRenderPipeline& renderPipeline,
-	RuntimeHost& runtimeHost,
-	CRITICAL_SECTION& mutex,
-	HDC hdc,
-	HGLRC hglrc) :
+	RenderEngine& renderEngine,
+	HealthTelemetry& healthTelemetry) :
 	mVideoIO(videoIO),
-	mRenderer(renderer),
-	mRenderPipeline(renderPipeline),
-	mRuntimeHost(runtimeHost),
-	mMutex(mutex),
-	mHdc(hdc),
-	mHglrc(hglrc)
+	mRenderEngine(renderEngine),
+	mHealthTelemetry(healthTelemetry)
 {
 }

@@ -46,7 +37,7 @@ void OpenGLVideoIOBridge::RecordFramePacing(VideoIOCompletionResult completionRe
 	else if (completionResult == VideoIOCompletionResult::Flushed)
 		++mFlushedFrameCount;

-	mRuntimeHost.GetHealthTelemetry().TryRecordFramePacingStats(
+	mHealthTelemetry.TryRecordFramePacingStats(
 		mCompletionIntervalMilliseconds,
 		mSmoothedCompletionIntervalMilliseconds,
 		mMaxCompletionIntervalMilliseconds,
@@ -58,38 +49,12 @@ void OpenGLVideoIOBridge::RecordFramePacing(VideoIOCompletionResult completionRe
 void OpenGLVideoIOBridge::VideoFrameArrived(const VideoIOFrame& inputFrame)
 {
 	const VideoIOState& state = mVideoIO.State();
-	mRuntimeHost.GetHealthTelemetry().TryReportSignalStatus(!inputFrame.hasNoInputSource, state.inputFrameSize.width, state.inputFrameSize.height, state.inputDisplayModeName);
+	mHealthTelemetry.TryReportSignalStatus(!inputFrame.hasNoInputSource, state.inputFrameSize.width, state.inputFrameSize.height, state.inputDisplayModeName);

 	if (inputFrame.hasNoInputSource || inputFrame.bytes == nullptr)
 		return;							// don't transfer texture when there's no input

-	const long textureSize = inputFrame.rowBytes * static_cast<long>(inputFrame.height);
-
-	// Never let input upload stall the playout/render callback. If the GL bridge
-	// is busy producing an output frame, skip this upload and use the next input.
-	if (!TryEnterCriticalSection(&mMutex))
-		return;
-
-	wglMakeCurrent(mHdc, mHglrc);		// make OpenGL context current in this thread
-
-	glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
-	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
-	glBindBuffer(GL_PIXEL_UNPACK_BUFFER, mRenderer.TextureUploadBuffer());
-	glBufferData(GL_PIXEL_UNPACK_BUFFER, textureSize, inputFrame.bytes, GL_DYNAMIC_DRAW);
-	glBindTexture(GL_TEXTURE_2D, mRenderer.CaptureTexture());
-
-	// NULL for last arg indicates use current GL_PIXEL_UNPACK_BUFFER target as texture data.
-	if (inputFrame.pixelFormat == VideoIOPixelFormat::V210)
-		glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, state.captureTextureWidth, state.inputFrameSize.height, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
-	else
-		glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, state.captureTextureWidth, state.inputFrameSize.height, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, NULL);
-
-	glBindTexture(GL_TEXTURE_2D, 0);
-	glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
-
-	wglMakeCurrent(NULL, NULL);
-
-	LeaveCriticalSection(&mMutex);
+	mRenderEngine.TryUploadInputFrame(inputFrame, state);
 }

 void OpenGLVideoIOBridge::PlayoutFrameCompleted(const VideoIOCompletion& completion)
@@ -104,15 +69,7 @@ void OpenGLVideoIOBridge::PlayoutFrameCompleted(const VideoIOCompletion& complet
 	frameContext.videoState = state;
 	frameContext.completion = completion;

-	EnterCriticalSection(&mMutex);
-
-	// make GL context current in this thread
-	wglMakeCurrent(mHdc, mHglrc);
-
-	mRenderPipeline.RenderFrame(frameContext, outputFrame);
-	wglMakeCurrent(NULL, NULL);
-
-	LeaveCriticalSection(&mMutex);
+	mRenderEngine.RenderOutputFrame(frameContext, outputFrame);

 	mVideoIO.EndOutputFrame(outputFrame);

--- a/apps/LoopThroughWithOpenGLCompositing/gl/pipeline/OpenGLVideoIOBridge.h
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/pipeline/OpenGLVideoIOBridge.h
@@ -2,24 +2,19 @@

 #include "OpenGLRenderPipeline.h"

-#include <windows.h>
-
 #include <chrono>
 #include <cstdint>

-class RuntimeHost;
+class HealthTelemetry;
+class RenderEngine;

 class OpenGLVideoIOBridge
 {
 public:
 	OpenGLVideoIOBridge(
 		VideoIODevice& videoIO,
-		OpenGLRenderer& renderer,
-		OpenGLRenderPipeline& renderPipeline,
-		RuntimeHost& runtimeHost,
-		CRITICAL_SECTION& mutex,
-		HDC hdc,
-		HGLRC hglrc);
+		RenderEngine& renderEngine,
+		HealthTelemetry& healthTelemetry);

 	void VideoFrameArrived(const VideoIOFrame& inputFrame);
 	void PlayoutFrameCompleted(const VideoIOCompletion& completion);
@@ -28,12 +23,8 @@ private:
 	void RecordFramePacing(VideoIOCompletionResult completionResult);

 	VideoIODevice& mVideoIO;
-	OpenGLRenderer& mRenderer;
-	OpenGLRenderPipeline& mRenderPipeline;
-	RuntimeHost& mRuntimeHost;
-	CRITICAL_SECTION& mMutex;
-	HDC mHdc;
-	HGLRC mHglrc;
+	RenderEngine& mRenderEngine;
+	HealthTelemetry& mHealthTelemetry;
 	std::chrono::steady_clock::time_point mLastPlayoutCompletionTime;
 	double mCompletionIntervalMilliseconds = 0.0;
 	double mSmoothedCompletionIntervalMilliseconds = 0.0;