关于directShow编程？

//After loading the source filter,
//retrieve a pointer to the IKsPropertySet, as follows.
CoInitialize(NULL);
IBaseFilter *pSrcFilter;
IKsPropertySet *pIPropertySet;
pSrcFilter->QueryInterface( IID_IKsPropertySet,(PVOID *)&pIPropertySet );//？？？？
CoUninitialize();

这段程序如何理解？
此外我想知道为什么我执行queryinterface时出错（编译通过，运行时报告该内存不能读）？？
是不是因为我没有用CoCreateInstance创建一个IBaseFilter？如果是，该如何创建？

谢谢！

因为你的 pSrcFilter 相当于未初始化。你需要用相关API创建一个IBaseFilter。

 

因为你的 pSrcFilter 相当于未初始化。你需要用相关API创建一个IBaseFilter。

请教大虾：具体如何做呢？给个引子吧！ :P

CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC,
IID_IGraphBuilder, (void **)&pGraph);

// Create the capture graph builder.
CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL, CLSCTX_INPROC,
IID_ICaptureGraphBuilder2, (void **)&pBuilder);
if(pGraph==NULL||pBuilder==NULL)
{
printf(\"1build base graph error\\n\");
CoUninitialize();
return;
}

pBuilder->SetFiltergraph(pGraph);    
// Create the system device enumerator.
ICreateDevEnum *pDevEnum = NULL;
CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC,
IID_ICreateDevEnum, (void **)&pDevEnum);

// Create an enumerator for video capture devices.
IEnumMoniker *pClassEnum = NULL;
pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pClassEnum, 0);


if (pClassEnum->Next(1, &pMoniker, &cFetched) == S_OK)
{
// Bind the first moniker to a filter object.
pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pSrc);
pMoniker->Release();
}
pClassEnum->Release();
pDevEnum->Release();
if(pSrc)
{
ll_return=pGraph->AddFilter(pSrc, L\"Video Capture\");
if(ll_return==S_OK)
{
printf(\"add video capture ok\\n\");
}
ll_return=pSrc->QueryInterface(IID_IAMCameraControl ,(void**)&pRemote);
if(ll_return==S_OK)
{
printf(\"get camera ok\\n\");
}
else
{
printf(\"get camera false\\n\");
}
}

[编辑 -  7/10/03 by  mike_wang]

//After loading the source filter,
//retrieve a pointer to the IKsPropertySet, as follows.
CoInitialize(NULL);
IBaseFilter* pSrcFilter=NULL;
IKsPropertySet* pIPropertySet=NULL;
//-------------
//....create your pSrcFilter
//-------------
if(pSrcFilter)
{
pSrcFilter->QueryInterface( IID_IKsPropertySet,(PVOID *)&pIPropertySet );//？？？？
}
CoUninitialize();