DirectShow（二）GraphEdit

• what
  1. GraphEdit is a visual tool for building and testing filter graphs.
  2. You can quickly build and test filter graphs to see if they function as you expect.
  3. You can even view a filter graph created by an application running in another process.
• ex.
  1. build filter graph

　　2.Load a Graph From an External Process(The application must register the filter graph instance in the Running Object Table (ROT).)。代码如下（在上一篇控制台程序中加入注册代码）：

#include "stdafx.h"
#include <DShow.h>
#define REGISTER_FILTERGRAPH

DWORD     g_dwGraphRegister=0;

HRESULT AddGraphToRot(IUnknown *pUnkGraph, DWORD *pdwRegister);
void RemoveGraphFromRot(DWORD pdwRegister);

int _tmain(int argc, _TCHAR* argv[])
{
	IGraphBuilder *pGraph = NULL;
	IMediaControl *pControl = NULL;
	IMediaEvent   *pEvent = NULL;

	// Initialize the COM library.
	HRESULT hr = CoInitialize(NULL);
	if (FAILED(hr))
	{
		printf("ERROR - Could not initialize COM library");
		return 1;
	}

	// Create the filter graph manager and query for interfaces.
	hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, 
		IID_IGraphBuilder, (void **)&pGraph);
	if (FAILED(hr))
	{
		printf("ERROR - Could not create the Filter Graph Manager.");
		return 1;
	}

	hr = pGraph->QueryInterface(IID_IMediaControl, (void **)&pControl);
	hr = pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent);

	// Build the graph. IMPORTANT: Change this string to a file on your system.
	hr = pGraph->RenderFile(L"E:\\red_sun.wmv", NULL);

#ifdef REGISTER_FILTERGRAPH
	if (SUCCEEDED(hr))
	{
		hr = AddGraphToRot(pGraph, &g_dwGraphRegister);
		if (FAILED(hr))
		{
			printf("Failed to register filter graph with ROT!");
			g_dwGraphRegister = 0;
		}
	}
#endif

	if (SUCCEEDED(hr))
	{
		// Run the graph.
		hr = pControl->Run();
		if (SUCCEEDED(hr))
		{
			// Wait for completion.
			long evCode;
			pEvent->WaitForCompletion(INFINITE, &evCode);

			// Note: Do not use INFINITE in a real application, because it
			// can block indefinitely.
		}
	}

#ifdef REGISTER_FILTERGRAPH
	if (g_dwGraphRegister)
	{
		RemoveGraphFromRot(g_dwGraphRegister);
		g_dwGraphRegister = 0;
	}
#endif

	pControl->Release();
	pEvent->Release();
	pGraph->Release();
	CoUninitialize();

	return 0;
}

#ifdef REGISTER_FILTERGRAPH

HRESULT AddGraphToRot(IUnknown *pUnkGraph, DWORD *pdwRegister) 
{
	IMoniker * pMoniker;
	IRunningObjectTable *pROT;
	if (FAILED(GetRunningObjectTable(0, &pROT))) 
	{
		return E_FAIL;
	}

	WCHAR wsz[128];
	wsprintfW(wsz, L"FilterGraph %08x pid %08x", (DWORD_PTR)pUnkGraph, 
		GetCurrentProcessId());

	HRESULT hr = CreateItemMoniker(L"!", wsz, &pMoniker);
	if (SUCCEEDED(hr)) 
	{
		// Use the ROTFLAGS_REGISTRATIONKEEPSALIVE to ensure a strong reference
		// to the object.  Using this flag will cause the object to remain
		// registered until it is explicitly revoked with the Revoke() method.
		//
		// Not using this flag means that if GraphEdit remotely connects
		// to this graph and then GraphEdit exits, this object registration 
		// will be deleted, causing future attempts by GraphEdit to fail until
		// this application is restarted or until the graph is registered again.
		hr = pROT->Register(ROTFLAGS_REGISTRATIONKEEPSALIVE, pUnkGraph, 
			pMoniker, pdwRegister);
		pMoniker->Release();
	}

	pROT->Release();
	return hr;
}

void RemoveGraphFromRot(DWORD pdwRegister)
{
	IRunningObjectTable *pROT;

	if (SUCCEEDED(GetRunningObjectTable(0, &pROT))) 
	{
		pROT->Revoke(pdwRegister);
		pROT->Release();
	}
}

#endif

运行程序，打开GraphEdit，File-->Connect to Remote Graph...即可看到如上图的filter graph，不过它是由我们的程序建立的。

参考：

     1、GraphEdit Help

     2、DirectShow Help